California Rule 1153.1 Compliance in 2026: Is Your Commercial Food Oven Ready for the Next NOx Requirement?
Commercial Food Oven Owners: The Zero-NOx Transition Is Getting Closer
If your facility operates commercial food ovens, bakery ovens, cooking ovens, tortilla ovens, smokehouses, roasters, dryers or other permitted commercial food-oven equipment in the South Coast AQMD jurisdiction, Rule 1153.1 – Emissions of Oxides of Nitrogen from Commercial Food Ovens deserves your attention.
South Coast AQMD adopted the current Rule 1153.1 amendment on August 4, 2023, and the rule establishes progressively tighter NOx requirements, including future zero-emission requirements for certain equipment categories.
And 2026 is an important year.
South Coast AQMD held a Rule 1153.1 Technology Check-In on February 3, 2026, followed by a Stationary Source Committee review on March 20, 2026. The District’s 2026 assessment found that zero-NOx standards remain technically feasible and cost-effective for certain smaller equipment categories, while larger units face greater cost and fuel-switching challenges.
The message for facility owners is simple:
Don’t wait until your oven is approaching a compliance trigger to start planning.
What Is California Rule 1153.1?
Rule 1153.1 controls NOx emissions from permitted commercial food ovens used to prepare food or products for making beverages for human consumption within the South Coast AQMD jurisdiction.
The regulated equipment can include:
Bakery ovens
Cooking ovens
Tortilla ovens
Drying ovens
Smokehouses
Roasters
Dryers
Other qualifying commercial food-oven equipment
The current rule establishes Phase I NOx limits, followed by future zero-emission requirements for specified categories.
What Are the Current NOx Requirements?
The 2023 amendment established Phase I limits of 30 ppm NOx for most commercial food-oven categories, while tortilla ovens heated solely by infrared burners have a 15 ppm NOx limit.
The rule then moves toward zero-emission requirements for specified equipment categories.
This is particularly important for equipment planning because a facility may need to consider:
NOx testing → equipment age → burner age → permit requirements → retrofit/replacement → electrification → future compliance
🚨 Major 2026 Rule 1153.1 Update
South Coast AQMD Completed a Technology Check-In
On February 3, 2026, South Coast AQMD held a public technology check-in for Rule 1153.1.
The purpose was to evaluate whether the technology and cost assumptions behind the future zero-NOx requirements remain appropriate.
The March 20, 2026 Stationary Source Committee materials reported an important conclusion:
Zero-NOx standards remain technically feasible and cost-effective for certain smaller units.
The District specifically reported zero-NOx standards as cost-effective for:
Bakery ovens ≤3 MMBtu/hr
Indirect-fired bakery ovens
Cooking ovens ≤3 MMBtu/hr
Smokehouses
For larger equipment, the District concluded that maintaining low-NOx requirements was appropriate because transitioning to zero emissions was not cost-effective at this time, with fuel-switching costs being a major factor.
Current status:
Staff did not recommend a rule change at the March 2026 technology check-in.
That makes the existing compliance roadmap especially important for businesses planning equipment upgrades or replacements.
What Is Coming Next?
The 2023 rule framework established future implementation dates for zero-emission requirements.
January 1, 2027
Phase II zero-emission requirements begin for applicable categories.
These include certain:
Bakery ovens ≤3 MMBtu/hr
Indirect-fired bakery ovens
Cooking ovens
Smokehouses
The specific compliance trigger for existing equipment can depend on the unit’s age and burner age, rather than simply the calendar date.
January 1, 2030
Phase III requirements apply to applicable categories under the rule framework.
The original rule development included additional time for larger equipment where zero-emission technology and electrification presented greater technical and economic challenges.
Important: Facility owners should evaluate the exact rule language, permit conditions, equipment age, burner age and applicable category before assuming a specific deadline applies to their equipment.
Why 2026 Is the Right Time to Start Planning
A major equipment transition cannot always happen overnight.
Zero-emission or electric commercial food ovens can require:
New equipment
Electrical infrastructure
Utility coordination
Facility modifications
Engineering studies
Permit review
Production planning
Installation time
Startup and compliance evaluation
South Coast AQMD has recognized that fuel-switching costs can significantly affect cost-effectiveness, especially for larger equipment.
So waiting until the last moment could create unnecessary operational pressure.
Smart approach:
Evaluate → Test → Plan → Upgrade → Verify → Comply
Rule 1153.1 Compliance Testing: Why It Matters
NOx compliance is not simply about installing a new burner or purchasing an electric oven.
Facilities need reliable information about actual equipment performance.
Depending on the applicable requirements, a compliance program can involve:
NOx emissions testing
CO emissions testing
Fuel-flow measurements
Heat-input calculations
Operating-condition verification
Test protocol preparation
Permit-condition review
Source-test reporting
Equipment certification or documentation
Compliance recordkeeping
Accurate testing provides facility owners with defensible emissions data and helps identify potential problems before they become larger compliance issues.
Pros of Rule 1153.1 Compliance & NOx Testing
✅ 1. Helps Demonstrate Compliance
Professional emissions testing can provide documented data supporting applicable NOx and CO compliance requirements.
✅ 2. Supports Cleaner Operations
Lower NOx emissions contribute to South Coast California’s broader air-quality objectives.
✅ 3. Helps Identify Problems Early
Testing can identify combustion or operational issues before they become more expensive problems.
✅ 4. Supports Equipment Planning
Reliable emissions data can help facility managers decide whether equipment should be maintained, retrofitted or replaced.
✅ 5. Helps Prepare for Zero-NOx Requirements
Early assessment provides more time to evaluate electrification and zero-emission options.
✅ 6. Can Reduce Last-Minute Compliance Risk
Planning ahead can reduce the chance of rushing through testing, permitting or equipment changes near a regulatory trigger.
Cons & Challenges
Compliance also creates real operational challenges.
❌ Testing Costs
Professional source testing requires specialized equipment, personnel and technical reporting.
❌ Production Coordination
Testing may need to be conducted under representative operating conditions, requiring coordination with production.
❌ Equipment Modification Costs
Some facilities may need burner modifications, controls or equipment replacement.
❌ Electrification Costs
For applicable zero-NOx equipment, electrical upgrades and utility infrastructure can become significant expenses.
❌ Potential Production Disruption
Equipment replacement or modification may require planned downtime.
❌ Technical Complexity
Understanding NOx limits, equipment categories, burner age, unit age, permit requirements and compliance schedules can be complicated.
How EES Helps With Rule 1153.1
Energy Environmental Solutions, Inc. — Your Compliance Partner
Rule 1153.1 compliance requires more than simply taking an emissions reading.
EES can help facilities build a practical compliance strategy around testing, documentation and engineering support.
1. Rule 1153.1 Compliance Evaluation
EES can review applicable equipment and help identify the relevant regulatory and testing requirements.
2. NOx Source Testing
EES provides professional source-testing support to measure NOx emissions under applicable test conditions.
3. CO Testing
Where required, EES can support carbon monoxide emissions testing and compliance evaluation.
4. Test Protocol Development
EES can help develop test protocols based on applicable regulatory requirements, permit conditions and facility operations.
5. Equipment Performance Evaluation
Testing data can help determine whether equipment is performing within applicable emission requirements.
6. Regulatory Reporting
EES can support the preparation of technical emissions reports and compliance documentation.
7. Engineering Studies
For facilities evaluating equipment upgrades or future compliance strategies, engineering support can help assess available options.
8. Zero-NOx & Electrification Planning
As facilities move toward future zero-emission requirements, EES can help customers evaluate the emissions-testing and compliance side of equipment transition planning.
Rule 1153.1 + Rule 1153: Don’t Confuse the Two
This is important for commercial bakeries.
Rule 1153
VOC emissions
Commercial Bakery Ovens
Rule 1153.1
NOx emissions
Commercial Food Ovens
A bakery facility may need to consider both rules, depending on its equipment and operations.
EES can help facilities evaluate their applicable air-quality testing requirements rather than treating each requirement in isolation.
Is Your Commercial Food Oven Ready?
Ask your environmental/compliance team:
☑ Do we know which Rule 1153.1 category applies to our oven?
☑ Do we know our current NOx emissions?
☑ When was our last NOx compliance test?
☑ How old is our oven?
☑ How old is the burner?
☑ Are our permits and equipment records current?
☑ Will future zero-NOx requirements affect our equipment?
☑ Will electrical infrastructure be required?
☑ Have we started planning for potential equipment replacement?
☑ Do we have a testing and compliance strategy?
If several answers are “No” or “I’m not sure,” now is the time to investigate.
Don’t Wait for the Deadline
California’s commercial food-oven regulatory landscape is moving toward lower and, for certain equipment categories, zero-NOx emissions.
The 2026 technology check-in confirmed that zero-NOx requirements remain viable for certain smaller equipment categories, while larger equipment continues to face technical and economic challenges.
Your equipment may have years of useful life left—but your compliance planning should start now.
Partner With EES
Accurate Testing. Reliable Results. Regulatory Confidence.
Energy Environmental Solutions, Inc.
Source Testing | Compliance | Engineering
Need Rule 1153.1 NOx Testing or Compliance Support?
Is Your Commercial Bakery Oven Ready for California Air Quality Compliance?
If you operate a commercial bakery, food manufacturing facility, bread production plant, or other operation using regulated bakery ovens in Southern California, South Coast AQMD Rule 1153 – Commercial Bakery Ovens may affect your facility.
Rule 1153 addresses Volatile Organic Compound (VOC) emissions from commercial bakery ovens. For facilities subject to the rule, demonstrating the required level of VOC emission reduction is an important part of maintaining environmental compliance.
And there is another reason bakery operators should be paying attention in 2026:
South Coast AQMD is continuing to move commercial food-oven regulations toward lower and zero-emission technologies under Rule 1153.1.
That means bakery and food-processing facilities should not wait until the next compliance deadline, equipment replacement or regulatory inspection to evaluate their emissions and testing requirements.
What Does Rule 1153 Cover?
South Coast AQMD Rule 1153 applies to commercial bakery ovens meeting specific heat-input and VOC-emission criteria.
The rule generally applies to bakery ovens with:
Rated heat input capacity of 2 million BTU/hour or more
Average daily VOC emissions of 50 pounds or more
VOC emissions associated with fermentation and baking of yeast-leavened products
Facilities should evaluate their individual equipment, permits, operating conditions and emissions before determining applicability.
What Are the Rule 1153 VOC Requirements?
For applicable existing bakery ovens, Rule 1153 establishes VOC emission-reduction requirements based on the oven’s emissions.
Existing Bakery Ovens
Depending on the applicable emissions category:
70% minimum VOC reduction
For an existing oven with base-year average daily VOC emissions of 50 pounds or more, but less than 100 pounds.
95% minimum VOC reduction
For an existing oven with base-year average daily VOC emissions of 100 pounds or more.
New Bakery Ovens
New bakery ovens subject to Rule 1153 generally require:
95% or greater VOC emission reduction when uncontrolled average daily VOC emissions are 50 pounds or more.
These requirements can make accurate emissions measurement and control-device performance evaluation extremely important.
Why Rule 1153 Compliance Testing Matters
A bakery may believe that its oven is operating normally, but normal production does not automatically mean regulatory compliance.
VOC emissions can be influenced by factors such as:
Yeast percentage
Fermentation time
Product type
Production rate
Oven operating conditions
Exhaust flow
Control-device performance
Changes in equipment configuration
Changes in production processes
A properly planned emissions test can help establish whether the equipment is achieving the required emission-reduction performance.
For facilities subject to source-testing requirements, testing should be planned around the applicable permit conditions, regulatory requirements, approved test methods and operating conditions.
2026 Update: Why Bakery Operators Should Also Watch Rule 1153.1
While Rule 1153 focuses on VOC emissions, Rule 1153.1 addresses NOx emissions from commercial food ovens.
This distinction is extremely important.
In 2026, South Coast AQMD conducted a technology check-in concerning the future zero-NOx requirements under Rule 1153.1.
The agency’s 2026 assessment reported that zero-NOx technology is technically feasible and cost-effective for smaller oven categories. At the same time, the agency recognized that transitioning from natural gas to electricity can create significant fuel-switching and infrastructure costs, particularly for larger ovens.
The 2026 activity included:
February 3, 2026 technology check-in
March 20, 2026 Stationary Source Committee discussion
April 3, 2026 Governing Board update
Continued evaluation of zero-NOx technology and cost-effectiveness
Continued preparation for future zero-emission requirements
Why Does This Matter to Bakery Facilities?
Because today’s VOC compliance project can become part of tomorrow’s broader emissions-management strategy.
Bakery operators should consider both:
VOC compliance under Rule 1153
and
NOx requirements under Rule 1153.1
when planning major oven modifications, burner replacements, electrification projects, new equipment purchases or facility expansions.
What Is Coming Under Rule 1153.1?
Rule 1153.1 establishes Phase I NOx requirements and future zero-emission requirements for certain commercial food ovens.
The zero-emission provisions include categories such as:
Certain bakery ovens rated at or below 3 MMBtu/hr
Certain cooking ovens rated at or below 3 MMBtu/hr
Indirect-fired bakery ovens
Smokehouses
The future compliance structure is based in part on equipment and burner age.
For affected facilities, the transition toward zero-NOx technology can involve:
Equipment evaluation
Electrical capacity assessment
Utility coordination
Permit planning
Equipment replacement or modification
Compliance testing
Engineering analysis
Documentation and reporting
The key message for facility owners: Don’t wait until an equipment deadline forces a rushed decision.
Pros of Rule 1153 Compliance & Emissions Testing
1. Helps Demonstrate Regulatory Compliance
Accurate testing provides documented emissions data that can support compliance demonstrations.
2. Identifies Emissions Problems Early
Testing can reveal problems with oven operation, exhaust systems or VOC control equipment before they become larger compliance concerns.
3. Supports Permit Compliance
Testing and reporting can help facilities maintain documentation associated with applicable permits and regulatory requirements.
4. Supports Better Equipment Decisions
Reliable emissions information can help facility managers determine whether to maintain, modify, upgrade or replace equipment.
5. Improves Environmental Performance
Effective VOC control can contribute to reduced ozone-forming emissions and improved regional air quality.
6. Helps Prepare for Future Regulations
With California continuing to move toward lower-emission and zero-emission technologies, early testing and engineering evaluation can help facilities prepare for future requirements.
Cons & Challenges of Rule 1153 Compliance
Compliance is important, but it can create practical challenges for bakery operators.
1. Testing Costs
Professional source testing requires specialized personnel, equipment, laboratory analysis and reporting.
2. Production Coordination
Testing often needs to occur under representative operating conditions, which requires coordination with production schedules.
3. Potential Control-System Upgrades
If testing identifies insufficient VOC reduction, the facility may need to evaluate control-device modifications or other corrective measures.
4. Operational Disruption
Poorly planned testing can interfere with production schedules.
5. Technical Documentation
Permit conditions, test protocols, operating parameters, calculations and final reports can be complicated.
6. Future Equipment Investment
The broader transition toward low-NOx and zero-NOx commercial food-oven technology may require significant capital planning, particularly where electrical upgrades or equipment replacement are necessary.
At Energy Environmental Solutions, Inc. (EES), we help industrial and commercial facilities approach air-quality compliance through professional testing, engineering support and regulatory documentation.
For bakery and food-processing facilities, EES can help with a compliance strategy that may include:
Rule 1153 Compliance Evaluation
Review the facility’s applicable equipment, operating conditions and regulatory requirements to help determine the appropriate compliance pathway.
VOC Source Testing
Perform emissions testing using applicable regulatory and approved test methodologies.
Test Protocol Development
Develop a testing strategy and protocol based on applicable requirements, permit conditions and facility operating parameters.
Emissions Measurement & Data Analysis
Collect and evaluate emissions data to support an accurate compliance determination.
Control-System Performance Evaluation
Where applicable, evaluate the performance of VOC emission-control equipment.
Compliance Reporting
Prepare technically organized documentation and reports to support regulatory compliance and facility records.
Rule 1153.1 Support
For facilities affected by commercial food-oven NOx requirements, EES can also support:
Environmental compliance is not simply about collecting numbers.
The quality of the testing plan, operating conditions, measurements, calculations and final documentation can all matter.
EES provides a coordinated approach:
PLAN → TEST → ANALYZE → REPORT → SUPPORT COMPLIANCE
Our goal is to help customers obtain accurate, defensible emissions data while minimizing unnecessary operational disruption.
Don’t Wait for a Compliance Problem
If your facility operates commercial bakery ovens in California, now is a good time to review your compliance position.
Ask yourself:
Is my bakery oven subject to Rule 1153?
Do I know my uncontrolled VOC emissions?
Is my VOC control system achieving the required reduction?
When was my last compliance test?
Are my testing records complete?
Does my current permit accurately reflect my equipment?
Could upcoming Rule 1153.1 requirements affect my equipment?
Will future electrification require electrical or utility upgrades?
Should I plan equipment modifications or replacement before a regulatory deadline?
If you cannot confidently answer these questions, a professional compliance review may be worthwhile.
Partner With EES for California Air Quality Compliance
Accurate Testing. Reliable Results. Regulatory Confidence.
Energy Environmental Solutions, Inc. helps facilities navigate complex air-emissions testing and compliance requirements with technical, engineering and testing support.
Protect Your Permit. Protect Your Operations. Prepare for What’s Next.
Rule 1146.2 in California 2026: Latest Updates, Pros, Cons & How EES Helps Industries
Rule 1146.2 is one of the most significant South Coast AQMD regulations affecting large water heaters, small boilers, process heaters, pool heaters, and certain high-temperature heaters. The rule is designed to reduce nitrogen oxide (NOx) emissions and, following its June 7, 2024 amendment, progressively moves covered equipment toward zero-NOx emissions.
The biggest Rule 1146.2 development in 2026 is no longer just the January 1 compliance deadline. On July 2, 2026, the Ninth Circuit Court of Appeals upheld South Coast AQMD’s amended Rule 1146.2, rejecting an industry challenge arguing that the regulation was preempted by federal energy-efficiency law. This is a major development because it strengthens the legal position of the District’s zero-NOx transition.
At the same time, the first major compliance milestone has already arrived: beginning January 1, 2026, certain Type 1 units ≤400,000 Btu/hr and instantaneous water heaters ≤200,000 Btu/hr installed in new buildings must meet zero-emission limits.
Important: Rule 1146.2 is not a statewide California regulation. It is a South Coast AQMD rule, applying within the District’s jurisdiction and subject to the rule’s applicability provisions and exemptions.
What Is Rule 1146.2?
South Coast AQMD’s Rule 1146.2 is titled:
“Emissions of Oxides of Nitrogen from Large Water Heaters and Small Boilers and Process Heaters.”
The rule was originally adopted in 1998 and subsequently amended several times. The current version was amended on June 7, 2024.
The 2024 amendment significantly changed the regulatory direction by establishing zero-NOx emission limits and a phased implementation schedule for covered equipment.
The regulation covers equipment categories that can include:
Large water heaters
Small boilers
Process heaters
Pool heaters
High-temperature heaters
Instantaneous water heaters
Other equipment meeting the rule’s definitions and applicability criteria
The exact applicability depends on equipment type, rated heat-input capacity, installation/building status, age, fuel and other conditions.
Why Is Rule 1146.2 Important in 2026?
There are three major reasons.
1. The first zero-emission deadline took effect
South Coast AQMD’s official 2026 compliance-deadline notice states that beginning January 1, 2026, certain Phase I equipment installed in new buildings must comply with zero-emission limits. Specifically, this includes Type 1 units with rated heat input capacity ≤400,000 Btu/hr and instantaneous water heaters ≤200,000 Btu/hr.
2. The Ninth Circuit upheld the rule
On July 2, 2026, the Ninth Circuit affirmed the lower court’s judgment in favor of South Coast AQMD in Rinnai America Corp. v. South Coast Air Quality Management District.
The court held that the Energy Policy and Conservation Act (EPCA) does not preempt Rule 1146.2, allowing the District’s zero-NOx emissions requirements to remain in place.
3. More deadlines are coming
The rule does not stop with 2026.
The current schedule establishes additional zero-emission deadlines in:
2028
2029
2031
2033
depending on equipment category and whether the unit is installed in a new or existing building.
That means businesses installing or replacing combustion equipment today should consider future compliance requirements, not only today’s requirements.
This is arguably the most important Rule 1146.2 development of 2026.
A coalition including appliance manufacturers and industry organizations challenged the rule, arguing that federal law preempted South Coast AQMD’s zero-NOx requirements.
On July 2, 2026, the Ninth Circuit rejected that argument and affirmed the lower court’s judgment for South Coast AQMD.
The court explained that the District adopted Rule 1146.2 as part of its effort to meet federal Clean Air Act ozone requirements.
The court’s opinion notes that the South Coast Air Basin faces severe ozone problems and that the District’s 2022 Air Quality Management Plan determined that widespread adoption of zero-emission technologies across stationary sources was necessary to achieve the required reductions.
What does this mean for industry?
It means companies should not assume that the zero-NOx provisions will disappear simply because they were challenged in court.
The Ninth Circuit decision substantially reinforces the legal status of the rule.
What Does Rule 1146.2 Require?
The 2024 amendment establishes zero-NOx limits for covered equipment according to phased implementation schedules.
The rule’s Table 2 establishes zero-emission limits for several categories, including:
Equipment Category
NOx Limit
Type 1 Unit
0 ppmv
Instantaneous Water Heater ≤200,000 Btu/hr
0 ppmv
Instantaneous Water Heater >200,000 Btu/hr
0 ppmv
Type 1 Pool Heater
0 ppmv
Type 2 Unit
0 ppmv
Type 1 High-Temperature Unit
0 ppmv
Type 2 High-Temperature Unit
0 ppmv
The applicable compliance date varies by category.
This is a fundamental shift from conventional low-NOx combustion requirements.
The direction is clear:
Low NOx → Ultra-Low NOx → Zero NOx
2026 Compliance Deadline
The first major phase began on:
January 1, 2026
For new buildings, Phase I applies to specified equipment, including:
Type 1 units ≤400,000 Btu/hr
Instantaneous water heaters ≤200,000 Btu/hr
These units must comply with the applicable zero-emission limits.
Existing buildings are subject to later deadlines depending on equipment category.
The current Rule 1146.2 schedule identifies:
Phase
New Buildings
Existing Buildings
Phase I
January 1, 2026
January 1, 2029
Phase II
January 1, 2028
January 1, 2031
Phase III
January 1, 2029
January 1, 2033
These dates are tied to the specific equipment categories in the rule.
Therefore, an existing facility should not automatically assume that it has a 2026 deadline.
The facility needs to determine:
What equipment do we have?
When was it installed?
What is its rated heat input?
Which category applies?
Is it in a new or existing building?
Which phase applies?
Rule 1146.2 Is Not Just About New Equipment
A common misconception is that Rule 1146.2 only matters when buying new equipment.
That’s not necessarily true.
The rule includes provisions concerning existing units, unit age, burner modifications/replacements and demonstrations of compliance.
For example, the rule states that after applicable Table 3 compliance dates, an owner/operator may not operate a unit that exceeds the applicable Table 2 emission limits once the unit reaches the specified age. It also addresses modifications and burner replacements.
This means a facility planning a burner replacement should evaluate the regulatory consequences before purchasing or installing the replacement.
Why Zero-NOx Technology?
Traditional combustion equipment generates NOx during high-temperature combustion.
Zero-emission technologies can eliminate combustion-related NOx at the equipment itself.
The District’s rationale is connected to the South Coast Air Basin’s severe ozone challenge. The Ninth Circuit opinion states that the District determined widespread zero-emission technology adoption was necessary to achieve the NOx reductions required for compliance with federal ozone standards.
This makes Rule 1146.2 part of a much broader air-quality strategy.
Pros of Rule 1146.2
1. Significant NOx Reduction
The most obvious advantage is reducing NOx emissions from covered combustion equipment.
Zero-NOx equipment can substantially reduce combustion-related emissions compared with conventional natural-gas-fired equipment.
2. Supports Better Air Quality
NOx contributes to ozone formation and other air-quality problems.
Reducing stationary-source NOx supports South Coast AQMD’s broader clean-air objectives.
3. Encourages Technology Innovation
The rule creates market demand for:
Electric water heating
Electric boilers
Heat-pump technology
Other zero-emission technologies
Advanced building systems
4. Provides a Long-Term Regulatory Roadmap
The phased schedule gives businesses several years to plan for future equipment transitions.
Instead of discovering a future requirement at the last minute, facility managers can incorporate it into capital planning.
5. Encourages Better Equipment Planning
Businesses replacing old equipment can evaluate whether the replacement will remain useful throughout its expected service life.
6. Supports Regional Ozone-Reduction Goals
The Ninth Circuit noted the District’s determination that significant additional NOx reductions were required to meet federal ozone standards.
Cons and Challenges of Rule 1146.2
1. Higher Initial Equipment Costs
Zero-emission equipment can cost more initially than conventional gas-fired equipment.
CARB’s current FAQ on zero-emission space and water heaters also notes that purchase and installation costs can be higher, particularly when electrical-panel, wiring, meter or utility upgrades are necessary.
2. Electrical Infrastructure
Switching from gas combustion to electric equipment may require:
Larger electrical service
New wiring
Panel upgrades
Utility coordination
Additional installation work
3. Facility Downtime
Replacing boilers, water heaters or process heaters can interrupt operations.
Facilities need careful project scheduling.
4. Capital Planning Challenges
Businesses may need to replace functioning equipment earlier than originally expected because of future compliance requirements.
5. Technology Availability
Some industrial applications have more straightforward zero-emission alternatives than others.
High-temperature or specialized process applications may require more complex engineering.
6. Workforce and Engineering Requirements
Facility teams may need electrical, mechanical and environmental expertise simultaneously.
A Major 2026 Legal Development: What Industry Should Know
The Ninth Circuit’s July 2026 ruling is especially important for businesses because it rejected the argument that federal energy-efficiency law preempted Rule 1146.2.
The court also emphasized that the rule regulates emissions, not simply energy efficiency.
It further noted that Rule 1146.2 includes process heaters, which are not among the products covered by EPCA’s federal efficiency standards, making the plaintiffs’ facial challenge unsuccessful.
Practical takeaway:
Businesses should plan around the current Rule 1146.2 requirements rather than assuming that litigation will suspend the rule.
Does Rule 1146.2 Require Source Testing?
Source testing remains relevant to Rule 1146.2 compliance.
South Coast AQMD publishes a specific:
Rule 1121/1146.2 NOx Compliance Testing Protocol for Water Heaters & Small Boilers
The District’s Methods & Procedures page identifies this protocol as part of its official source-testing materials.
Rule 1146.2 also contains provisions allowing certain modified units to demonstrate compliance through source testing conducted according to South Coast AQMD Source Test Method 100.1 by an independent testing laboratory.
This is where professional testing becomes valuable.
Why Compliance Testing Still Matters in a Zero-NOx Transition
You might ask:
“If the new standard is zero emissions, why would testing still matter?”
Because the transition doesn’t happen overnight.
Facilities continue to operate existing equipment during the phase-in period, and some equipment may use compliance demonstrations, retrofit provisions, certification or other mechanisms specified by the rule.
Testing can help establish:
Actual emissions
Equipment performance
Compliance status
Baseline conditions
Retrofit effectiveness
Documentation for regulatory review
South Coast AQMD also operates a Laboratory Approval Program (LAP) under which independent source-testing firms are evaluated for specific methods and technical capabilities.
Certified Equipment Is Becoming More Important
South Coast AQMD maintains a certified equipment list for Rule 1146.2.
The District’s certified-equipment page currently identifies the Rule 1146.2 certified boilers list as last updated December 30, 2025.
The dedicated Rule 1146.2 support page also provides access to the certified equipment information.
For contractors, developers and facility owners, checking equipment certification before purchasing can help avoid expensive compliance surprises.
What Industries Should Pay Attention to Rule 1146.2?
Potentially affected operations include:
Commercial buildings
Hotels
Hospitals
Universities
Apartment buildings
Restaurants
Food-processing facilities
Manufacturing plants
Industrial facilities
Warehouses with process heating
Swimming-pool facilities
Commercial water-heating operations
Industrial process-heating operations
The exact applicability depends on the equipment and the rule’s definitions and exemptions.
Rule 1146.2 2026
Rule 1146.2 Compliance Checklist for 2026
Facility owners and environmental managers should review:
Where a unit has been modified or retrofitted, testing can help demonstrate emissions performance when the applicable rule provision requires it.
CEMS / RATA / CGA Support
For facilities with applicable continuous monitoring systems or related requirements, EES can provide specialized emissions-monitoring support.
Engineering Studies
EES can help facilities understand their current emissions and evaluate potential compliance strategies.
Regulatory Documentation
Testing is only useful when the results are properly documented.
EES can support the technical reporting process associated with emissions testing.
Rule 1146.2 Compliance Strategy for 2026
A smart facility strategy can be divided into five steps:
1. Identify
Determine exactly which Rule 1146.2 provisions apply to each unit.
2. Measure
Establish actual emissions and operating performance where testing is required or useful.
3. Evaluate
Compare the equipment’s current status with the applicable limits and deadlines.
4. Plan
Determine whether the facility needs:
Retrofit
Replacement
Electrification
Process modification
Electrical upgrades
Additional testing
5. Act
Complete the required compliance work before the applicable deadline.
Rule 1146.2: Pros vs. Cons
Pros
Cons
Major NOx reductions
Higher equipment costs
Supports cleaner air
Potential electrical upgrades
Encourages zero-emission technology
Installation complexity
Long-term regulatory roadmap
Possible equipment replacement
Promotes technology innovation
Production downtime
Reduces combustion-related emissions
Specialized engineering may be needed
Helps meet ozone-reduction goals
Capital-planning burden
What Should Businesses Do Now?
The most important lesson from the 2026 developments is simple:
Don’t wait for your deadline to start planning.
If your facility operates a water heater, boiler or process heater affected by Rule 1146.2, determine its regulatory status now.
A useful first step is to create an equipment inventory containing:
Model → Size → Age → Fuel → Location → Certification → Current emissions → Applicable deadline
Then compare that information against the current Rule 1146.2 requirements.
This can reveal whether your facility needs testing, certification review, retrofit planning or equipment replacement.
Final Takeaway: Rule 1146.2 in 2026
Rule 1146.2 represents a major shift in Southern California’s approach to combustion equipment.
The rule is moving covered equipment toward zero-NOx emissions, with phased deadlines extending from 2026 through 2033.
The first Phase I deadline began on January 1, 2026, and the July 2, 2026 Ninth Circuit decision upheld the rule against an industry preemption challenge.
For industry, the message is clear:
Measure your emissions. Understand your deadline. Plan your equipment transition.
And don’t treat Rule 1146.2 as simply a future issue.
2026 is already the beginning of the compliance transition.
Rule 1146 in California 2026: Latest Updates, Pros, Cons & How EES Helps Industries
Rule 1146 — Emissions of Oxides of Nitrogen from Industrial, Institutional and Commercial Boilers, Steam Generators, and Process Heaters is one of the key South Coast AQMD regulations governing NOx emissions from larger combustion equipment.
A major development for 2026 is that Rule 1146 is actively being reconsidered. The current adopted rule was amended on December 4, 2020, but South Coast AQMD is now conducting a new Proposed Amended Rule 1146 (PAR 1146) rulemaking. The District held Working Group Meeting #3 on February 13, 2026 and Working Group Meeting #4 on June 25, 2026, showing that the amendment process is actively progressing.
Important: Rule 1146 is not a statewide California rule. It is a South Coast AQMD rule, so its requirements apply to qualifying sources within the District’s jurisdiction. The current rule covers industrial, institutional and commercial boilers, steam generators and process heaters with rated heat-input capacity generally 5 MMBtu/hr or greater, subject to the rule’s applicability and exemptions.
For companies operating boilers and process heaters, 2026 is therefore a good time to review emissions performance, testing schedules and upcoming regulatory changes.
What Is California Rule 1146?
South Coast AQMD Rule 1146 controls NOx emissions from industrial, institutional and commercial boilers, steam generators and process heaters.
These combustion systems are commonly found in:
Manufacturing facilities
Food-processing plants
Pharmaceutical facilities
Hospitals and institutions
Commercial facilities
Chemical manufacturing
Industrial heating operations
Steam-generation systems
Thermal-fluid heating applications
The current Regulation XI rulebook identifies Rule 1146 as “Emissions of Oxides of Nitrogen from Industrial, Institutional and Commercial Boilers, Steam Generators, and Process Heaters”, amended December 4, 2020.
The regulation is designed primarily around reducing NOx, a pollutant that contributes to ozone and particulate pollution.
Boiler Testing Company
Why Is Rule 1146 Important in 2026?
The biggest reason is simple:
Rule 1146 is currently under active amendment discussions.
South Coast AQMD’s official PAR 1146/1146.1 page lists:
Working Group #1 — November 13, 2024
Working Group #2 — April 24, 2025
Working Group #3 — February 13, 2026
Working Group #4 — June 25, 2026
The District also lists a March 27, 2026 stakeholder comment letter from the SoCal Clean Manufacturing Coalition.
This is significant for industry because the regulatory framework could evolve even though the currently adopted Rule 1146 has not yet been replaced by a new final rule.
In other words:
2026 is a monitoring-and-preparation year—not a reason to assume that proposed requirements are already mandatory.
Facilities should continue complying with the currently effective rule and permit conditions while following the proposed amendment process.
Latest 2026 Update: Proposed Amended Rule 1146
South Coast AQMD’s current rulemaking page confirms that the District is actively working on amendments to Rule 1146 and Rule 1146.1.
The proposed amendment is particularly important because the District is evaluating NOx requirements for combustion equipment against evolving Best Available Retrofit Control Technology (BARCT) and air-quality objectives.
The proposal process includes technical discussions with stakeholders, meaning facility owners, environmental managers, equipment manufacturers and testing professionals have an opportunity to understand where the regulation may be heading.
But there is an important compliance distinction:
A proposed amendment is not the same thing as an adopted regulation.
Companies should not replace their current compliance program based solely on a draft presentation or proposed rule language.
Instead, they should:
Monitor → Evaluate → Test → Plan → Prepare
What Equipment Does Rule 1146 Cover?
Rule 1146 generally applies to boilers, steam generators and process heaters with rated heat input of 5 MMBtu/hr or greater, subject to specific exclusions and provisions.
The rule has historically established different NOx requirements based on equipment characteristics, including size and fuel type.
Examples of potentially regulated equipment include:
Industrial Boilers
Used to generate steam for manufacturing, heating or processing.
Steam Generators
Used where steam is an essential part of production or facility operations.
Process Heaters
Used to provide direct or indirect heat for industrial processes.
Thermal Fluid Heaters
Certain thermal-fluid heating systems can also fall within Rule 1146 requirements.
What Are the Current NOx Limits?
One of the most important things to understand about Rule 1146 is that there is not one universal NOx limit.
The applicable limit depends on the equipment category, size, fuel and other rule provisions.
Current regulatory summaries identify limits including:
Equipment Category
Current NOx Requirement*
Large units ≥75 MMBtu/hr
5 ppm
Units ≥20 and <75 MMBtu/hr
5–9 ppm, depending on applicable group/sub-tier
Units ≥5 and <20 MMBtu/hr
7–9 ppm
Atmospheric units
12 ppm
Digester-gas units
15 ppm
Landfill-gas units
25 ppm
Certain other gaseous-fuel units
30 ppm
Non-gaseous-fuel units
40 ppm
*Limits and applicability depend on the specific rule provisions, equipment configuration, fuel and permit conditions. Current technical summaries report these values at 3% O₂, dry basis.
This is why simply saying “California Rule 1146 requires 5 ppm” is misleading.
The correct question is:
“Which Rule 1146 category applies to my equipment?”
Rule 1146 Source Testing Requirements
Source testing is an important part of demonstrating compliance.
Current compliance information indicates that source-testing frequency is related to equipment size and operating characteristics.
For example, current industry compliance guidance reports:
Units ≥10 MMBtu/hr — generally tested every 3 years
Units >2 and <10 MMBtu/hr under the related Rule 1146.1 framework — generally tested every 5 years
Rule 1146 and Rule 1146.1 also contain periodic portable-analyzer monitoring requirements.
The exact obligation should always be confirmed against the current rule and the facility’s permit.
Portable Analyzer Testing Is Also Important
Rule 1146 compliance isn’t limited to occasional stack testing.
Periodic NOx and CO checks using an approved portable analyzer are also part of the compliance framework.
Current guidance indicates that Rule 1146 units may require portable analyzer testing monthly or every 750 operating hours, with opportunities for an extended schedule under specified compliance conditions. If a unit fails a check, the testing frequency can revert to the more frequent schedule.
Missing a periodic monitoring event can become a compliance-management problem even when the equipment itself is functioning properly.
CEMS Requirements
Certain large Rule 1146 units may require Continuous Emissions Monitoring Systems (CEMS).
Current guidance identifies, for example, CEMS requirements associated with certain units having rated heat-input capacity of 40 MMBtu/hr or greater and specified annual heat input.
CEMS compliance can involve:
NOx monitoring
Oxygen monitoring
Calibration
Certification
Quality assurance
Data validation
RATA
CGA
Recordkeeping
Reporting
This creates an additional layer of technical responsibility for large industrial boilers.
Why NOx Testing Matters
NOx isn’t simply another number on a laboratory report.
During combustion, high-temperature processes can produce nitrogen oxides. In the atmosphere, NOx participates in reactions that contribute to ozone formation and particulate pollution.
Southern California has historically faced serious ozone and air-quality challenges.
That is why stationary combustion sources such as boilers and process heaters remain an important part of the South Coast AQMD regulatory strategy.
Rule 1146 is one component of the broader NOx-control framework.
2026 Regulatory Direction: Why Facilities Should Pay Attention
South Coast AQMD’s current 2026 activity shows that Rule 1146 is being actively evaluated.
The District’s proposed-rule page confirms the June 25, 2026 Working Group #4 meeting, while the February 2026 meeting was Working Group #3.
This suggests that facilities should expect continued technical discussion around the regulation.
Potential areas of concern for industry include:
Future NOx limits
BARCT assessments
Compliance timelines
Monitoring requirements
Source testing
CEMS
Equipment upgrades
Existing-unit provisions
New-unit requirements
Economic impacts
Again, these should be treated as rulemaking considerations until formally adopted.
Pros of Rule 1146
1. Lower NOx Emissions
The strongest benefit is reduced NOx emissions from industrial combustion equipment.
For applicable large combustion units, EES can assist with emissions-monitoring programs.
RATA & CGA
EES can support applicable Relative Accuracy Test Audits (RATA) and Cylinder Gas Audits (CGA).
Engineering Studies
When emissions are approaching regulatory limits, engineering analysis can help identify potential causes and improvement strategies.
Regulatory Reporting
EES can help organize technical documentation and compliance reporting following testing.
Industries That May Need Rule 1146 Support
Potentially affected industries include:
Manufacturing
Food processing
Pharmaceutical manufacturing
Chemical manufacturing
Hospitals
Universities
Commercial facilities
Industrial steam generation
Metal processing
Textile manufacturing
Paper manufacturing
Plastics manufacturing
Industrial process heating
Thermal-fluid heating operations
Applicability depends on the specific equipment, fuel, heat input, permit and regulatory status.
Rule 1146 vs. Rule 1146.1 vs. Rule 1146.2
These rules are frequently confused.
Rule
General Equipment Size
Main Focus
Rule 1146
≥5 MMBtu/hr
Industrial, institutional & commercial boilers, steam generators & process heaters
Rule 1146.1
>2 to <5 MMBtu/hr
Small boilers, steam generators & process heaters
Rule 1146.2
≤2 MMBtu/hr
Large water heaters and small boilers/process heaters
South Coast AQMD’s regulatory materials distinguish these three rules according to equipment size and type.
This distinction matters because testing schedules and emission limits can differ.
2026 Pros vs. Cons at a Glance
Pros
Cons
Reduces NOx
Testing costs
Improves air quality
Possible equipment upgrades
Encourages low-NOx technology
Production interruptions
Provides measurable emissions data
Monitoring workload
Supports proactive maintenance
CEMS costs for applicable units
Improves compliance documentation
Potential uncertainty from proposed amendments
Supports regional clean-air goals
Complex requirements for large facilities
Why Businesses Should Prepare Now
The 2026 amendment process creates a useful opportunity for businesses to examine their current emissions before regulatory requirements potentially change.
South Coast AQMD has already held multiple stakeholder working-group meetings for PAR 1146/1146.1, including two meetings in 2026.
This doesn’t mean every facility needs to replace its boiler today.
It means facility owners should know their numbers.
Ask yourself:
When was my boiler last tested?
What is the current NOx level?
What is my applicable limit?
How often am I required to monitor?
Is my burner operating efficiently?
Could my equipment meet a more stringent future requirement?
If you don’t know the answers, now is the right time to investigate.
The Bottom Line for Rule 1146 in 2026
Rule 1146 remains an important South Coast AQMD NOx regulation for industrial, institutional and commercial boilers, steam generators and process heaters.
The current adopted rule was amended in December 2020, while Proposed Amended Rule 1146 is actively being developed in 2026, with Working Group #4 held on June 25, 2026.
The proposed amendment should not be described as a final 2026 regulation yet. Facilities should continue following the currently effective rule and permit requirements while monitoring the rulemaking process.
For industrial operators, the smartest strategy is straightforward:
Rule 1147.2 in California 2026: Latest Updates, Pros, Cons & How EES Helps Industries
Rule 1147.2 — NOx Reductions from Metal Melting and Heating Furnaces is a key South Coast AQMD regulation for facilities operating permitted metal melting, metal heat-treating, metal heating, and metal forging furnaces.
A critical clarification before discussing 2026: Rule 1147.2 is not a statewide California regulation. It is a South Coast AQMD rule applicable within the District’s jurisdiction when the equipment meets the rule’s applicability requirements. The current official rule is identified as Rule 1147.2, adopted April 1, 2022.
As of August 2026, the official South Coast AQMD material reviewed does not show a newly adopted 2026 amendment replacing Rule 1147.2. However, 2026 remains important because South Coast AQMD has an active rulemaking agenda with more than two dozen planned amendments/adoptions across its regulatory program, while the agency continues implementing measures aimed at reducing emissions and improving air quality.
For metal-processing facilities, the practical question is therefore not simply, “Was Rule 1147.2 changed in 2026?” It is:
“Is my furnace currently meeting the applicable Rule 1147.2 limits, testing schedule, permit conditions and monitoring requirements?”
That’s where professional source testing and compliance support become valuable.
Energy Environmental Solutions, Inc. (EES) can help industries with Rule 1147.2 source testing, NOx testing, CO testing, compliance test protocol development, CEMS, RATA, CGA, engineering studies, emissions monitoring and regulatory reporting.
What Is Rule 1147.2?
Rule 1147.2 was created specifically to reduce nitrogen oxide (NOx) and carbon monoxide (CO) emissions from four major categories of combustion equipment:
Metal melting furnaces
Metal heat-treating furnaces
Metal heating furnaces
Metal forging furnaces
The rule applies to an owner or operator of one of these furnaces when the equipment requires a South Coast AQMD permit.
The regulation was developed as part of South Coast AQMD’s broader transition away from the RECLAIM program toward more source-specific emissions controls. South Coast AQMD documents describe Rule 1147.2 as moving metal melting and heating furnace operations from Rule 1147 into a dedicated rule with NOx limits reflecting current BARCT — Best Available Retrofit Control Technology.
That makes Rule 1147.2 particularly relevant to businesses in the metal-processing sector.
Why Does Rule 1147.2 Matter in 2026?
NOx is a major precursor to ozone and particulate pollution. In Southern California, reducing stationary-source NOx remains an important component of regional air-quality planning.
South Coast AQMD’s 2026 outlook identifies extensive rulemaking activity intended to implement the 2016 and 2022 Air Quality Management Plans and the 2024 PM Plan, reduce health risks, and support attainment of state and federal air-quality standards.
That means industrial facilities shouldn’t treat Rule 1147.2 as an old compliance document sitting in a filing cabinet.
And 2026 is especially relevant for facilities managing multiple furnaces because some of the rule’s multi-unit implementation schedule reaches 100% compliance milestones in 2026 and beyond.
Latest Rule 1147.2 Updates for 2026
1. The Current Adopted Rule Is Still the April 1, 2022 Rule
The official South Coast AQMD rulebook identifies Rule 1147.2 as:
Rule 1147.2 — NOx Reductions from Metal Melting and Heating Furnaces Adopted: April 1, 2022
The current official rule remains the primary document facilities should use when evaluating compliance in 2026.
There is an important distinction between current regulatory obligations and future rulemaking activity.
A facility shouldn’t assume that every item appearing on a proposed-rule page is already law.
2. 2026 Is an Important Milestone for Multiple-Furnace Facilities
One of the most relevant provisions for 2026 is the multiple-unit implementation schedule.
For facilities with two or more applicable units, Rule 1147.2 provides a phased approach based on the percentage of total rated heat-input capacity represented by units covered by the implementation schedule.
The rule specifies a January 1, 2026 milestone requiring:
100% of applicable rated heat-input capacity for facilities with 2–9 units
67% for facilities with 10–19 units
The schedule continues to January 1, 2028, when 100% applies to the 20-or-more-unit category under the specified schedule.
Why is this important?
A company operating one furnace may have a relatively straightforward compliance program.
A company operating 10, 15 or 20 furnaces has a much more complicated compliance calendar.
For those facilities, 2026 is not simply another year on the calendar—it can represent a significant implementation milestone.
3. Rule 1147.2 Has Different Limits for Different Furnaces
One of the biggest mistakes a facility can make is assuming there is one universal NOx limit for every furnace.
There isn’t.
For existing units below 40 MMBtu/hr, Table 1 establishes different NOx limits depending on furnace type and operating temperature.
Existing Furnace
NOx Limit
CO Limit
Metal Melting
40 ppm
1,000 ppm
Metal Heat Treating / Heating / Forging ≤1,200°F
40 ppm
—
Metal Heat Treating / Heating / Forging >1,200°F
50 ppm
—
Radiant-Tube Burners
50 ppm
—
Units ≥40 MMBtu/hr
15 ppm
—
The applicable ppm limits are corrected to 3% oxygen on a dry basis, with an 8-hour rolling average applying where specified for units equipped with certified NOx CEMS.
That means compliance testing has to be designed around the actual furnace configuration.
4. New Units Face Different Requirements
Rule 1147.2 also establishes a separate Table 3 for new units.
For example:
Metal melting furnaces below 40 MMBtu/hr: 40 ppm NOx
Metal heat treating/heating/forging ≤1,200°F: 30 ppm NOx
Metal heat treating/heating/forging >1,200°F: 40 ppm NOx
Radiant-tube burners: 40 ppm NOx
Units ≥40 MMBtu/hr: 15 ppm NOx
The rule specifies the applicable oxygen correction and averaging provisions.
This is an important consideration when a facility is replacing an old furnace.
Replacing equipment does not necessarily mean you can simply carry the old compliance assumptions into the new installation.
5. Burner Age Can Affect Implementation
For certain units below 40 MMBtu/hr, Rule 1147.2 uses burner age as part of its implementation schedule.
For applicable existing units, facilities need to determine burner age using documentation such as:
Burner manufacturer invoices
Previous permit applications
Manufacturer identification/rating plates
Other substantiated written information approved by the Executive Officer
Where burner age cannot be determined through the specified methods, the rule provides a default treatment.
This makes equipment records extremely important.
Think of burner documentation as part of your compliance evidence.
If you don’t know when the burner was installed, you may have difficulty determining which implementation pathway applies.
6. Source Testing Is a Core Requirement
Rule 1147.2 contains specific source-testing requirements.
For units subject to the applicable concentration limits:
Units below 10 MMBtu/hr
A source test is required no later than 60 calendar months from the previous source test.
Units ≥10 MMBtu/hr
The testing interval depends on annual heat input:
≤23 billion Btu/year: up to 60 months
>23 billion Btu/year: up to 36 months
These requirements are based on the rule’s specified testing provisions.
This means the test frequency isn’t necessarily determined by furnace size alone.
Annual heat input can matter.
7. New Furnaces Have an Initial Testing Requirement
For new units, Rule 1147.2 requires an initial source test no later than 18 months after the Permit to Construct is issued, unless the Executive Officer approves an extension in writing.
For existing units, the rule establishes its own initial testing provisions and allows certain previously conducted South Coast AQMD-approved source tests to be used when the specified conditions are satisfied.
This creates an important project-management requirement:
Environmental compliance should be included in the equipment installation schedule from the beginning.
Don’t wait until the furnace is commissioned and production is underway to start thinking about source testing.
8. A Test Protocol Must Be Submitted Before Testing
Rule 1147.2 requires the source-test protocol to be submitted to the Executive Officer for approval at least 90 days before the scheduled source test.
The rule also specifies when the actual test must occur relative to protocol approval.
This is one of the strongest reasons to work with an experienced source-testing company.
A compliance test is not simply:
“Bring the analyzer → measure emissions → issue a report.”
Rule 1147.2 specifies approved source-testing procedures, including applicable South Coast AQMD methods and EPA Method 19, with alternative methods requiring the appropriate advance approvals.
The rule specifically references methods including:
South Coast AQMD Method 100.1
South Coast AQMD Method 7.1
South Coast AQMD Method 10.1
EPA Method 19
It also requires compliance source testing to use a South Coast AQMD-approved contractor under the Laboratory Approval Program for the applicable procedures.
That makes contractor selection a compliance issue—not merely a purchasing decision.
10. Source-Test Reports Have a 60-Day Deadline
After testing, Rule 1147.2 requires source-test reports to be submitted to the Executive Officer within 60 days of completion of the source test.
This creates three separate deadlines that facility managers should track:
Protocol submission → Test date → Report submission
A facility can conduct a technically successful test and still create a compliance problem if the required documentation isn’t handled correctly.
11. Large Furnaces May Require CEMS
For units with a rated heat-input capacity of 40 MMBtu/hr or greater, Rule 1147.2 includes CEMS requirements for measuring NOx and oxygen under specified facility circumstances.
The rule references applicable requirements under South Coast AQMD Rules 218.2 and 218.3, and Rule 2012 for certain RECLAIM facilities.
This means large-furnace compliance may involve much more than periodic stack testing.
Facilities may need to manage:
CEMS → Certification → QA/QC → RATA → Monitoring → Data validation
That is where specialized environmental testing expertise becomes especially valuable.
Pros of Rule 1147.2
1. Lower NOx Emissions
The primary benefit is reduced NOx emissions from metal-processing furnaces.
Lower NOx supports regional efforts to improve ozone and particulate pollution.
2. Better Combustion Performance
Testing can identify combustion problems involving:
Burner settings
Air/fuel ratio
Excess oxygen
Burner deterioration
Furnace operation
Control systems
3. More Transparent Compliance
Measured emissions data provide a stronger compliance record than relying solely on theoretical calculations.
4. Encourages Cleaner Technology
The regulation can encourage facilities to consider:
Low-NOx burners
Improved combustion controls
Burner modernization
Better monitoring
Furnace upgrades
5. Supports Long-Term Planning
A structured testing program gives facility managers better information about equipment performance.
6. Helps Reduce Community Exposure
Metal-processing facilities can be located near industrial communities. Reducing combustion-related pollutants can support broader air-quality objectives.
Cons and Challenges of Rule 1147.2
1. Testing Costs
Professional source testing requires specialized personnel, equipment, calibration, field measurements, data analysis and reporting.
2. Production Disruption
Testing must be coordinated with furnace operations and production schedules.
3. Equipment Upgrades Can Be Expensive
Older burners may not easily achieve newer emission limits without modification or replacement.
4. Multiple Units Increase Compliance Complexity
Facilities with many furnaces may have different:
Burner ages
Heat-input ratings
Operating temperatures
Emission limits
Test frequencies
Permit conditions
5. CEMS Adds Another Layer
Large units may have continuing CEMS-related responsibilities involving certification, maintenance and performance testing.
6. Documentation Is Critical
Permit records, burner-age documentation, source-test reports and monitoring records need to remain organized.
What Industries Should Pay Attention to Rule 1147.2?
Potentially affected operations include facilities involved in:
Metal Casting
Foundries
Metal Forging
Heat Treating
Metal Heating
Aluminum Processing
Steel Processing
Iron Processing
Nonferrous Metal Manufacturing
Industrial Furnace Operations
Metal Fabrication
The exact applicability depends on the equipment and permit.
Rule 1147.2 Compliance: What Should a Facility Check?
A facility manager should review the following:
Is the furnace subject to Rule 1147.2?
What type of furnace is it?
What is its rated heat-input capacity?
What is the burner age?
What is the applicable NOx limit?
Does a CO limit apply?
Is the unit a new or existing unit?
Is the facility RECLAIM, former RECLAIM or non-RECLAIM?
When was the last source test?
When is the next test due?
Is the source-test protocol approved?
Is CEMS required?
Are RATA/CGA requirements applicable?
Are the required permits current?
Are source-test reports submitted on time?
Are records complete?
How EES Helps With Rule 1147.2 Compliance
Energy Environmental Solutions, Inc. (EES) provides environmental testing and engineering support to industrial facilities.
Rule 1147.2 Source Testing
EES can help facilities perform compliance source testing for applicable metal-processing furnaces.
NOx Testing
Accurate NOx measurement is fundamental to demonstrating compliance with Rule 1147.2.
CO Testing
Where applicable, EES can support CO emissions testing alongside NOx measurements.
For large furnaces subject to CEMS requirements, EES can support emissions monitoring programs.
RATA & CGA
EES can assist facilities with applicable Relative Accuracy Test Audits (RATA) and Cylinder Gas Audits (CGA).
Engineering Studies
EES can evaluate combustion performance and help facilities understand potential compliance strategies.
Regulatory Reporting
After testing, EES can assist with technical documentation and reporting.
Rule 1147.2 Testing Process
A professional compliance project can be organized into the following stages:
1. Permit Review
Review the current South Coast AQMD permit and equipment information.
2. Applicability Review
Determine exactly how Rule 1147.2 applies to the furnace.
3. Limit Identification
Determine the applicable NOx and CO limits.
4. Testing Schedule
Calculate when the next source test is due.
5. Protocol Development
Develop and submit the source-test protocol.
6. Field Testing
Conduct the required emissions measurements under appropriate operating conditions.
7. QA/QC
Review calibration, sampling and analytical data.
8. Emissions Calculations
Calculate concentrations and applicable emission rates.
9. Reporting
Prepare and submit the source-test report.
10. Follow-Up
If results indicate noncompliance, evaluate appropriate corrective actions.
Why Proactive Rule 1147.2 Testing Is Important in 2026
South Coast AQMD’s 2026 regulatory agenda demonstrates that the District continues to actively develop and implement air-quality controls. The agency says its 2026 rule calendar contains more than two dozen planned rule amendments and adoptions aimed at implementing air-quality plans, reducing health risks and improving compliance clarity.
That doesn’t mean Rule 1147.2 itself was amended in 2026.
It means the regulatory environment surrounding industrial emissions continues to evolve.
A facility that waits until an inspection, permit renewal or failed test to examine its furnace emissions may have fewer options than a facility that monitors performance proactively.
Rule 1147.2: 2026 Pros vs. Cons
Pros
Cons
Reduces NOx emissions
Source testing costs
Supports cleaner air
Production scheduling challenges
Encourages modern burners
Potential equipment upgrades
Provides measurable compliance data
Complex requirements for multiple furnaces
Helps identify combustion problems
CEMS obligations for certain large units
Improves regulatory readiness
Detailed documentation required
Supports long-term environmental planning
Testing must follow approved methods
The 2026 Takeaway
Rule 1147.2 remains an important compliance requirement for applicable metal-processing furnaces in the South Coast AQMD jurisdiction.
The current adopted rule dates to April 1, 2022, and the official material reviewed does not show a replacement 2026 amendment. At the same time, 2026 includes important implementation and regulatory-planning milestones, particularly for facilities with multiple furnaces.
For facility managers, the smartest approach is not to wait for a regulatory surprise.
Know your furnace. Know your burner age. Know your NOx limit. Know your testing frequency. Know your permit. Know your CEMS obligations.
And most importantly:
Know whether your emissions data can demonstrate compliance.
Rule 1147.1 in California 2026: Latest Updates, Pros, Cons & How EES Helps Aggregate-Drying Facilities
Rule 1147.1 — NOx Reductions from Aggregate Dryers is an important South Coast AQMD regulation affecting certain aggregate-drying operations in Southern California. The rule establishes NOx and CO emission limits, source-testing requirements, monitoring provisions, recordkeeping, and compliance obligations for applicable aggregate dryers.
For 2026, there is an important distinction to make: Rule 1147.1 is not a statewide California regulation. It is a South Coast AQMD rule that applies within the District’s jurisdiction when the equipment meets the rule’s applicability requirements. South Coast AQMD’s current Regulation XI rulebook identifies Rule 1147.1 as “NOx Reductions from Aggregate Dryers,” adopted August 6, 2021.
At the same time, South Coast AQMD’s current proposed-rules pages continue to list Proposed Rule 1147.1 among rules in the proposal process. The dedicated proposal page, however, contains rulemaking documents dating primarily from 2020–2021. Therefore, businesses should not interpret that listing alone as evidence that a new Rule 1147.1 amendment was adopted in 2026.
For aggregate producers, asphalt and construction-material facilities, and other operations using regulated dryers, the practical message is simple:
Know your applicable NOx limit, know your testing deadline, and verify that your aggregate dryer can demonstrate compliance.
Energy Environmental Solutions, Inc. (EES) can help facilities with Rule 1147.1 source testing, NOx testing, CO testing, compliance test protocol development, emissions measurements, CEMS/RATA support, engineering studies, QA/QC and regulatory reporting.
What Is Rule 1147.1?
Rule 1147.1 was adopted by the South Coast AQMD Governing Board on August 6, 2021. It specifically addresses NOx reductions from aggregate dryers and was created as part of South Coast AQMD’s broader strategy to transition NOx sources away from the RECLAIM trading program toward more direct, source-specific controls.
The rule applies to qualifying gaseous-fuel-fired aggregate dryers with more than 1 pound per day of NOx emissions and a rated heat-input capacity greater than 2 million Btu/hour, subject to the rule’s detailed applicability provisions and exemptions.
Aggregate dryers are used to remove moisture from materials such as sand, gravel, crushed stone and other aggregate products. Because the drying process commonly involves high-temperature combustion, the burners can generate NOx.
And here’s the important part:
The larger the combustion system and the higher its emissions, the more important compliance testing becomes.
Why Does Rule 1147.1 Matter in 2026?
NOx is a major air pollutant involved in the formation of ground-level ozone and particulate matter. Southern California has historically faced significant challenges meeting federal and state air-quality standards, so stationary combustion sources remain an important part of regional emission-reduction strategies.
South Coast AQMD specifically developed Rule 1147.1 to establish NOx and CO requirements for aggregate dryers at non-RECLAIM, RECLAIM and former-RECLAIM facilities, together with monitoring, reporting and recordkeeping provisions.
The District’s planning documents estimate that Rule 1147.1 contributes additional NOx reductions as part of the transition from RECLAIM to command-and-control requirements. One South Coast AQMD emissions-inventory document identifies an estimated 0.01 tons/day of NOx reduction by 2030 attributable to Rule 1147.1, with implementation beginning in 2025 and reductions continuing toward 2057.
So while Rule 1147.1 is not a brand-new 2026 regulation, its compliance requirements remain relevant.
Latest 2026 Rule 1147.1 Update: What Facilities Should Know
1. The Current Adopted Rule Is Still Dated August 6, 2021
South Coast AQMD’s current official Regulation XI listing identifies:
Rule 1147.1 — NOx Reductions from Aggregate Dryers Adopted: August 6, 2021
Unlike several other South Coast AQMD rules that received amendments in 2025 or 2026, the current rulebook does not identify a 2026 amendment to Rule 1147.1.
That is an important SEO and compliance point because online articles sometimes describe old proposed-rule documents as if they were new 2026 regulations.
For 2026, facilities should work from:
The currently adopted Rule 1147.1 + their current South Coast AQMD permit + any applicable compliance conditions.
2. Proposed Rule 1147.1 Still Appears on South Coast AQMD’s Proposal Page
There is an unusual point worth highlighting.
South Coast AQMD’s current Active Proposed Rules page lists Proposed Rule 1147.1.
However, the dedicated Rule 1147.1 proposal page presents the original rulemaking materials, including the August 6, 2021 Notice of Public Hearing, July 2021 draft language and 2021 staff documents.
Therefore, companies should be careful when reading search results about “new Rule 1147.1 updates.”
The safest interpretation in 2026 is:
Rule 1147.1 remains an adopted South Coast AQMD rule, while the District’s website also retains/list its proposed-rule project materials. There is no verified evidence in the current official rulebook that a new 2026 amendment has replaced the adopted August 2021 rule.
This distinction is particularly important when preparing a compliance test.
3. NOx and CO Limits Remain Central
Rule 1147.1 establishes a 30 ppm NOx limit and 1,000 ppm CO limit, corrected to 3% oxygen on a dry basis, for the applicable gaseous-fuel-fired aggregate dryers under the rule’s relevant provisions.
The rule also established interim requirements for certain facilities during implementation.
The 2021 adoption materials identify:
Requirement
Rule 1147.1 Provision
Primary NOx limit
30 ppm
CO limit
1,000 ppm
Oxygen correction
3% O₂, dry
Applicability threshold
>1 lb/day NOx
Rated heat-input threshold
>2 MMBtu/hr
Source testing
Required for applicable units
Large dryers ≥40 MMBtu/hr
Annual testing
The precise applicability and compliance pathway should always be confirmed against the current rule and permit.
4. Source Testing Frequency Depends on Dryer Size
One of the most important Rule 1147.1 requirements for facility managers is the periodic source-testing schedule.
The current rule provides different testing frequencies based on the aggregate dryer’s rated heat-input capacity.
Aggregate dryer below 10 MMBtu/hr
Source testing is required every 5 calendar years, with the rule restricting how early the subsequent test can occur.
Aggregate dryer ≥10 and <40 MMBtu/hr
Source testing is required every 3 calendar years, again subject to the minimum interval specified by the rule.
Aggregate dryer ≥40 MMBtu/hr
Source testing is required every calendar year.
For a large dryer that has not operated for at least six consecutive months, the rule also provides a provision allowing the source test to occur within 90 days after operations resume, subject to the rule’s conditions and fuel-use documentation.
Why This Matters for 2026
Imagine an aggregate dryer operating at 45 MMBtu/hr.
Its operator cannot treat compliance testing as something to think about every three or five years.
The applicable rule calls for annual source testing.
Now consider a facility operating several dryers of different sizes. The testing calendar can become complicated very quickly.
That is why environmental managers should maintain a centralized compliance schedule containing:
Equipment identification
Burner age
Rated heat input
Applicable NOx limit
Applicable CO limit
Last source-test date
Next source-test deadline
Permit conditions
Protocol approval
Test report submission date
Maintenance records
Missing a testing deadline can turn a technical compliance requirement into an operational problem.
5. Source-Test Reports Must Be Submitted
Rule 1147.1 requires source-test reports to be submitted to the Executive Officer within 60 days of completion of the test.
That means the project does not end when the field testing is complete.
The complete compliance cycle is:
Plan → Protocol → Test → QA/QC → Calculations → Report → Submission → Recordkeeping
A technically excellent field test can still create headaches if the final report is incomplete, inaccurate or submitted late.
6. Five-Year Recordkeeping Requirement
Rule 1147.1 requires source-test records to be maintained for five years and made available to South Coast AQMD personnel upon request.
This is especially important for companies with multiple facilities or multiple aggregate dryers.
Environmental records should not be scattered across emails, maintenance folders and individual computers.
A better approach is to maintain a centralized compliance file for every regulated unit.
7. Existing CEMS and Monitoring Systems Matter
Rule 1147.1 does not simply require every aggregate dryer to install a brand-new CEMS.
However, qualifying facilities with existing continuous in-stack emissions monitoring systems or equivalent verification systems must retain and operate them according to the applicable requirements.
The rule also allows certain other required testing or monitoring activities to satisfy a source-test requirement under specified conditions.
For example, qualifying:
Title V periodic monitoring/testing, or
RATA associated with CEMS
may be used to satisfy one instance of periodic source testing when the requirements of the rule are met.
This can potentially reduce duplicate testing—but only when the regulatory conditions are satisfied.
Rule 1147.1 Compliance: Pros
1. Reduces NOx Emissions
The biggest environmental advantage is straightforward: lower NOx emissions from aggregate-drying operations.
NOx reductions support South Coast AQMD’s broader efforts to improve regional air quality.
2. Encourages Modern Combustion Technology
Older burners can have substantially different emissions performance from newer low-NOx systems.
Rule 1147.1 creates an incentive for facilities to evaluate burner technology and combustion performance.
3. Provides Measurable Compliance
Instead of relying entirely on equipment specifications, source testing gives the facility actual emissions data.
4. Identifies Equipment Problems
Testing can uncover issues involving:
Burner performance
Combustion-air ratios
Fuel/air control
Temperature
Draft
Excess oxygen
Maintenance
Instrumentation
5. Improves Regulatory Documentation
A well-prepared test report provides evidence that the facility is monitoring its environmental performance.
6. Supports Long-Term Air-Quality Planning
South Coast AQMD’s Rule 1147.1 strategy is part of the District’s broader transition from RECLAIM to direct emissions limits.
Rule 1147.1 Compliance: Cons & Challenges
1. Source Testing Costs Money
Qualified source testing requires trained personnel, specialized instruments, calibration, field work, calculations and reporting.
2. Production Scheduling Can Be Difficult
Aggregate facilities cannot always stop or modify production simply to accommodate a test.
Testing must often occur under representative operating conditions.
3. Burner Replacement Can Be Expensive
Facilities with older burners may need to evaluate replacement or upgrades to maintain compliance.
4. Multiple Dryers Increase Complexity
A facility operating several aggregate dryers may have different:
Heat-input ratings
Burner ages
Permit conditions
Testing frequencies
Compliance deadlines
5. Compliance Data Must Be Defensible
Incorrect oxygen correction, sampling problems, calibration issues or unsuitable operating conditions can compromise a test.
6. Regulatory Interpretation Can Be Complex
Rule 1147.1 interacts with permits, monitoring requirements and the broader South Coast AQMD regulatory structure.
That is why facilities should not rely solely on a generic internet summary.
What Does an Aggregate Dryer Test Measure?
A Rule 1147.1 compliance test can involve measurement of NOx and CO, along with supporting measurements necessary to establish compliance under the applicable test method and permit.
Depending on the test protocol, testing may involve:
NOx concentration
CO concentration
Oxygen
Carbon dioxide
Stack gas conditions
Gas flow
Moisture
Fuel usage
Production rate
Dryer operating temperature
Burner operating conditions
The data are then evaluated against the applicable regulatory limit.
The goal is not simply to produce numbers.
The goal is to produce defensible compliance evidence.
Why Compliance Test Protocol Development Matters
Before testing begins, facilities should determine exactly how the test will be performed.
A compliance test protocol can identify:
Applicable regulations
Permit conditions
Emission limits
Sampling locations
Test methods
Number of test runs
Operating conditions
QA/QC requirements
Calculations
Reporting requirements
Rule 1147.1 requires applicable source testing and approved testing procedures under its compliance provisions.
A poorly planned test can create unnecessary risk.
Protocol first. Testing second.
How EES Helps Industries With Rule 1147.1
Energy Environmental Solutions, Inc. (EES) provides environmental testing and compliance support for industrial facilities.
Rule 1147.1 Source Testing
EES can support compliance testing for applicable aggregate dryers, including NOx and CO measurements.
NOx Testing
Accurate NOx measurement is at the center of Rule 1147.1 compliance.
CO Testing
The rule also establishes CO requirements, making reliable CO measurement important.
Where applicable, EES can support continuous emissions monitoring and associated performance testing.
Engineering Studies
EES can help facilities evaluate combustion equipment, emissions trends and potential control strategies.
Regulatory Reporting
EES can assist with technical documentation and reporting following source testing.
Industries That May Need Rule 1147.1 Support
Potentially affected operations can include facilities involved in:
Aggregate production
Sand and gravel processing
Crushed stone production
Construction materials
Asphalt-related material production
Mineral processing
Aggregate drying
Other operations using qualifying aggregate dryers
Applicability must be confirmed against the actual equipment and permit.
Rule 1147.1 vs. Rule 1147
These rules are easy to confuse.
Rule
Primary Focus
Rule 1147
NOx reductions from miscellaneous combustion sources
Rule 1147.1
NOx reductions from aggregate dryers
Rule 1147.2
NOx reductions from metal melting and heating furnaces
South Coast AQMD adopted Rule 1147.1 specifically to separate aggregate dryers from the broader miscellaneous-source framework.
This distinction matters when determining the applicable emission limits and testing requirements.
2026 Rule 1147.1 Compliance Checklist
If your facility operates an aggregate dryer in the South Coast AQMD jurisdiction, review:
Is the dryer subject to Rule 1147.1?
What is its rated heat-input capacity?
Is its NOx emission level above the applicability threshold?
What NOx limit applies?
What CO limit applies?
When was the burner installed?
When was the last source test?
When is the next test due?
Is the testing contractor appropriately qualified/approved?
Is the test protocol ready?
Are operating conditions representative?
Are calibration records current?
Are CEMS/RATA requirements applicable?
Are source-test reports submitted within the required timeframe?
Are five years of records available?
The 2026 Takeaway for Aggregate Facilities
The biggest misunderstanding about Rule 1147.1 is thinking:
“It is a 2021 rule, so it isn’t a 2026 issue.”
That’s not how environmental compliance works.
A rule can remain unchanged while its testing deadlines, permit conditions and operational obligations continue year after year.
For applicable aggregate dryers, Rule 1147.1 establishes a structured framework around NOx and CO emissions, periodic source testing, monitoring, reporting and recordkeeping. South Coast AQMD’s current rulebook continues to identify the adopted rule, while the District’s current proposal pages still reference Proposed Rule 1147.1 materials.
Don’t wait for the next compliance deadline.
If your aggregate dryer is approaching its source-test date, now is the time to verify:
Your permit. Your emission limits. Your testing frequency. Your protocol. Your equipment condition. Your records.
Need Rule 1147.1 Testing in California?
Energy Environmental Solutions, Inc. (EES) helps industrial facilities with:
Rule 1147.1 Source Testing | Aggregate Dryer Testing | NOx Testing | CO Testing | Compliance Test Protocol Development | Source Testing | Stack Testing | CEMS | RATA | CGA | Engineering Studies | QA/QC | Regulatory Reporting
Measure Emissions. Verify Compliance. Protect Your Operations.
Rule 1147 in California 2026: Latest Updates, Pros, Cons & How EES Helps Industries
Rule 1147 — NOx Reductions from Miscellaneous Sources is an important South Coast AQMD regulation for certain fuel-fired combustion equipment in Southern California. It is designed to reduce nitrogen oxide (NOx) emissions while limiting carbon monoxide (CO) from permitted gaseous- and liquid-fuel-fired equipment that is not covered by another applicable Regulation XI rule.
Important: Rule 1147 is not a statewide California rule. It applies within the South Coast AQMD jurisdiction to equipment meeting the rule’s applicability requirements. Other California air districts have their own rules and permit requirements.
For industrial facilities operating spray-booth heaters, ovens, dryers, furnaces, thermal oxidizers, afterburners, vapor incinerators, tenter-frame dryers, process heaters and other miscellaneous combustion equipment, understanding the current Rule 1147 requirements can be critical to avoiding compliance problems.
Energy Environmental Solutions, Inc. (EES) helps facilities with Rule 1147 source testing, NOx testing, CO testing, compliance test protocol development, emissions testing, CEMS/RATA/CGA, engineering studies and regulatory reporting.
What Is South Coast AQMD Rule 1147?
Rule 1147 was adopted in 2008 and most recently amended on May 6, 2022. The current South Coast AQMD rulebook identifies it as Rule 1147 — NOx Reductions from Miscellaneous Sources.
The rule applies to certain gaseous- and/or liquid-fuel-fired combustion equipment requiring a South Coast AQMD permit, when another Regulation XI rule does not already apply to the unit.
Covered equipment can include categories such as:
Thermal oxidizers
Catalytic oxidizers
Afterburners
Vapor incinerators
Ovens
Dryers
Dehydrators
Heaters
Furnaces
Kilns
Calciners
Cookers
Roasters
Tenter-frame dryers
Fabric and carpet dryers
Remediation units
Certain liquid-fuel-fired equipment
The exact applicability depends on the equipment, fuel, rated heat-input capacity, permit status and other provisions of the rule.
Why Does Rule 1147 Matter in 2026?
The environmental reason is straightforward: NOx contributes to ozone and particulate pollution, making NOx reductions an important component of regional air-quality planning.
South Coast AQMD’s Rule 1147 technology assessment explains that the rule’s NOx reductions are an important part of the region’s attainment strategy for federal and state ambient air-quality standards, including standards for ozone, PM2.5 and PM10.
And the need for effective air-quality controls remains highly relevant in 2026. South Coast AQMD’s current 2026 news and regulatory activity includes ozone advisories, particulate-related actions, toxic-air-contaminant rulemaking and additional emissions-control initiatives.
The compliance message for industry:
NOx compliance is not simply about installing a burner or combustion system. Facilities need to demonstrate that applicable equipment actually operates within its required emissions limits.
Latest Rule 1147 Updates for 2026
1. The Current Rule Remains the May 6, 2022 Version
As of August 2026, South Coast AQMD’s current Regulation XI listing identifies Rule 1147 as amended May 6, 2022. There is no indication on the current official rule listing of a newer 2026 amendment to Rule 1147 itself.
That distinction is important.
“Latest 2026 update” does not mean Rule 1147 itself was amended in 2026. Instead, facilities need to consider the current Rule 1147 requirements alongside their current permits and other 2026 regulatory developments.
2. Source Testing Remains a Major Compliance Requirement
For units subject to Rule 1147 with NOx emissions of at least 1 pound per day, the rule requires source testing to demonstrate compliance with applicable NOx and CO limits in the rule or permit.
The testing frequency depends on the equipment’s Rated Heat Input Capacity:
Rated Heat Input Capacity
Source-Test Frequency
< 10 MMBtu/hr
Every 5 calendar years
≥ 10 and < 40 MMBtu/hr
Every 3 calendar years
≥ 40 MMBtu/hr
Every calendar year
≥40 MMBtu/hr with ≥6 months shutdown
Test within 90 days after resumed operation, subject to the rule’s conditions
These intervals are specified in Rule 1147 paragraph (h)(12).
This is one of the most important points for facility managers:
Your source-test due date can depend directly on the equipment’s rated heat-input capacity and NOx emissions.
3. Rule 1147 Requires an Approved Test Protocol
Source testing isn’t simply a matter of sending a technician to the facility and taking measurements.
Rule 1147 requires the operator to submit a source-test protocol to the Executive Officer for approval no later than 90 days before the scheduled source test, subject to the rule’s timing provisions.
For subsequent compliance determinations, protocol resubmission may not be necessary when an approved protocol already exists, provided the unit has not been modified in a way requiring a permit modification and the applicable limits have not become more stringent.
Why does this matter?
Because an improperly planned test can create unnecessary delays, additional costs and potentially unusable compliance data.
Test planning should happen before the test day—not after.
4. Independent Testing Is Required
Rule 1147 requires compliance determinations to be conducted by an independent contractor approved by the Executive Officer under the Laboratory Approval Program for the applicable test methods.
That means facilities should verify that their selected testing company has the appropriate qualifications and approvals for the methods being used.
This is particularly important when a facility is approaching a regulatory deadline.
5. Recordkeeping Still Matters
Rule 1147 requires source-test reports and maintenance records to be maintained for at least five years and made available to South Coast AQMD personnel upon request.
This means compliance doesn’t end when the testing crew leaves the site.
Your facility should maintain:
Source-test reports
Maintenance records
Rated heat-input information
Fuel records where applicable
CEMS records where applicable
Compliance documentation
Approved testing protocols
Equipment modification records
Good documentation can be as important as good testing.
What Emission Limits Does Rule 1147 Establish?
Rule 1147 contains different NOx and CO limits depending on the equipment category, fuel type, process temperature and whether the unit is an in-use unit or subject to the newer Table 2 requirements.
For example, Table 1 includes different limits for equipment such as thermal oxidizers, ovens, heaters, dryers and other combustion equipment.
For certain gaseous-fuel-fired thermal oxidizers, catalytic oxidizers, afterburners and vapor incinerators, the Table 1 NOx limit is 60 ppmv or 0.073 lb/MMBtu, with a CO limit of 1,000 ppmv.
Table 2 establishes more stringent requirements for applicable equipment.
For example, gaseous-fuel-fired thermal oxidizers, catalytic oxidizers, afterburners and vapor incinerators are listed at 20 ppmv or 0.024 lb/MMBtu NOx under Table 2.
Do not assume these numbers automatically apply to your equipment. The applicable limit must be determined from the rule, equipment category, permit and compliance schedule.
A Key 2026 Compliance Option: Less Than 1 Pound of NOx Per Day
Rule 1147 provides an alternative pathway for certain units.
An owner or operator may elect to comply by demonstrating NOx emissions below 1 pound per day averaged over a calendar month, or by meeting an existing permit limit below 1 pound per day, whichever is applicable under the rule.
However, if the facility fails to demonstrate compliance with that option, additional permit and compliance requirements can be triggered.
This makes accurate emissions calculations and recordkeeping particularly important.
Pros of Rule 1147 Compliance
1. Lower NOx Emissions
The primary environmental benefit is reduced NOx emissions from miscellaneous combustion sources.
Lower NOx contributes to regional efforts to address ozone and particulate pollution. South Coast AQMD describes Rule 1147’s NOx reductions as an important component of its attainment strategy.
2. Better Combustion Performance
Testing can reveal problems involving burners, combustion-air systems, controls or operating conditions.
A failed or borderline test can therefore become an opportunity to identify equipment problems.
3. More Reliable Compliance Data
Professional source testing provides measured emissions data instead of relying exclusively on theoretical calculations or equipment specifications.
4. Better Maintenance Decisions
Testing results can help environmental and maintenance teams identify whether combustion equipment needs adjustment, repair or modernization.
5. Improved Regulatory Readiness
Maintaining current testing and maintenance records can make inspections and compliance reviews easier.
Cons and Challenges of Rule 1147
1. Testing Costs
Source testing requires specialized equipment, qualified personnel, laboratory or analytical resources and technical reporting.
2. Production Disruption
Testing may need to occur under specific operating conditions, which can require coordination with production schedules.
3. Protocol Approval Takes Planning
The requirement for an approved test protocol means facilities need to start preparing well before the actual test date.
4. Equipment Modifications Can Change Requirements
Changes to burners, combustion systems, fuel systems or operating conditions may affect the compliance pathway.
5. Multiple Equipment Categories
Rule 1147 covers a wide variety of equipment, so the correct testing approach is not identical for every unit.
6. Testing at the Wrong Operating Condition Can Create Problems
Rule 1147 specifies operating conditions for compliance determinations, including testing at the maximum heat-input range at which the unit normally operates and additional conditions for specified equipment categories.
What Equipment Should California Facilities Review?
If your facility is located in the South Coast AQMD jurisdiction, review Rule 1147 applicability if you operate permitted fuel-fired equipment such as:
The actual applicability must be confirmed against the current rule and permit.
How EES Helps With Rule 1147 Compliance
Energy Environmental Solutions, Inc. (EES) provides technical testing and environmental compliance support for industrial facilities.
Rule 1147 Source Testing
EES can assist with testing programs designed to demonstrate applicable NOx and CO emission compliance.
Compliance Test Protocol Development
EES helps develop testing protocols covering:
Sampling locations
Applicable test methods
Operating conditions
Test runs
QA/QC
Calculations
Reporting requirements
NOx Testing
Accurate NOx measurements are central to Rule 1147 compliance.
CO Testing
Rule 1147 also establishes CO requirements for applicable equipment, making CO testing an important part of many compliance demonstrations.
CEMS / RATA / CGA
For facilities using continuous emissions monitoring systems, EES can support applicable CEMS, RATA and CGA requirements.
Rule 1147 also provides circumstances in which qualifying periodic monitoring or CEMS relative-accuracy testing may be used as part of the source-testing compliance schedule.
Engineering Studies
EES can help facilities evaluate combustion-system performance, emissions trends and potential compliance strategies.
Regulatory Reporting
Testing isn’t complete until the data have been properly evaluated and documented.
EES can help prepare organized technical reports and supporting documentation.
Rule 1147 Compliance Testing Process
A professional compliance project generally follows this sequence:
1. Review the Permit Determine the applicable permit limits and conditions.
2. Confirm Rule Applicability Determine whether Rule 1147 applies to the unit.
3. Determine Testing Frequency Review NOx emissions and rated heat-input capacity.
4. Develop the Test Protocol Select appropriate methods and operating conditions.
5. Submit for Approval Follow South Coast AQMD protocol-approval requirements.
6. Conduct Field Testing Perform NOx, CO and supporting measurements.
7. QA/QC Review Review calibration, field data and calculations.
8. Calculate Emissions Determine compliance with the applicable limit.
9. Prepare the Report Document the test conditions, methods, results and conclusions.
10. Maintain Records Retain required documentation for the applicable period.
Why Proactive Rule 1147 Testing Makes Sense in 2026
South Coast AQMD states that its compliance staff conduct regular inspections to ensure equipment and processes are operating in compliance with applicable clean-air rules.
The agency also explains that failure to correct a Notice to Comply can lead to a Notice of Violation and penalties, while continuing violations can result in daily penalties.
That is why waiting until an inspector identifies a problem is a risky compliance strategy.
A better approach:
Know your limit. Know your test date. Know your operating conditions. Know your documentation.
Rule 1147 Compliance Checklist for 2026
Before your next test, review:
Is the unit subject to Rule 1147?
Is the current permit available?
What NOx limit applies?
What CO limit applies?
What is the unit’s rated heat-input capacity?
Is NOx ≥1 lb/day?
When was the last approved source test?
Is the next test due?
Has the test protocol been approved?
Has the equipment been modified?
Are operating conditions representative?
Are maintenance records current?
Are required fuel meters installed and maintained?
Are five years of required records available?
Is the testing contractor appropriately approved?
2026 Bottom Line
Rule 1147 remains an important South Coast AQMD NOx-compliance requirement in 2026. Although the rule itself was last amended on May 6, 2022, its current requirements continue to govern applicable miscellaneous combustion equipment, including specific source-testing frequencies, test protocols, NOx/CO limits and recordkeeping requirements.
For facilities with applicable equipment, the biggest mistake is assuming that “the equipment has always passed” means the next test can be treated casually.
VOC Destruction Efficiency in California 2026: Latest Updates, Pros, Cons & How EES Helps Industries
VOC destruction efficiency is a critical performance measure for California facilities that use thermal oxidizers, regenerative thermal oxidizers (RTOs), flares, and other air-pollution control systems to reduce volatile organic compound (VOC) emissions.
In 2026, California’s air-quality regulatory environment continues to place strong emphasis on emissions reduction, source testing, monitoring, control-device performance, and accurate reporting. South Coast AQMD has active rulemaking involving VOC-generating industries, including aerospace, wood-product coatings, marine coatings, solvents, and other industrial sources. Rule 1124 for aerospace assembly and component manufacturing was amended on April 3, 2026, while additional VOC-related rulemaking remains active during 2026.
For industries using thermal oxidation, the message is straightforward: having a control device installed is not the same as proving that it is achieving the required VOC control performance. Facilities may need reliable testing and documentation showing that their equipment operates within applicable permit and regulatory requirements.
Energy Environmental Solutions, Inc. (EES) helps industries with VOC Destruction Efficiency Testing, RTO Testing, Thermal Oxidizer Testing, VOC Source Testing, Stack Testing, NOx and CO Testing, Compliance Test Protocol Development, CEMS, RATA, CGA, Engineering Studies, QA/QC, and Regulatory Reporting.
What Is VOC Destruction Efficiency?
VOC destruction efficiency describes the percentage of VOC entering a control device that is destroyed before the treated gas leaves the system. A commonly used calculation is Destruction Efficiency (%) = [(VOC Inlet − VOC Outlet) ÷ VOC Inlet] × 100. For example, if a control device receives 100 units of VOC and 1 unit remains at the outlet, the calculated destruction efficiency is 99%.
That sounds simple, but industrial testing is rarely that simple. Inlet and outlet concentrations, gas flow, moisture, oxygen, temperature, production rate, fuel usage, and other operating conditions can all influence the final result. A facility also needs to understand whether its permit requires destruction efficiency, removal efficiency, capture efficiency, overall control efficiency, or a specific outlet concentration, because these measurements are not interchangeable.
South Coast AQMD’s emissions-reporting guidance specifically says that site-specific test results, the applicable permit, or the applicable rule limit should be used when determining vapor destruction efficiency for certain thermal-oxidation applications.
Is VOC Destruction Efficiency Testing Compulsory in California?
There is an important distinction for facility owners and environmental managers.
There is no single statewide VOC destruction-efficiency testing requirement that applies identically to every California facility. The requirement depends on the facility’s Air District, permit conditions, source category, control equipment, pollutants, applicable state and federal requirements, and specific regulatory provisions.
For example, a Bay Area Air Quality Management District permit for thermal oxidizers establishes a minimum VOC destruction efficiency of 95% by weight along with minimum operating temperatures and continuous temperature monitoring.
Another Bay Area permit issued in 2025 for regenerative thermal oxidizers establishes different destruction-efficiency requirements depending on inlet VOC concentration: greater than 98.5% for higher inlet concentrations, greater than 98% for intermediate concentrations, and greater than 90% for lower concentrations, with an alternative outlet concentration limit also specified. The permit also establishes a minimum combustion-zone temperature and continuous temperature monitoring.
This illustrates why companies should not simply advertise or assume that “99% destruction efficiency” is automatically the legal requirement for every California operation.
Your permit determines what your facility must demonstrate.
Latest California VOC & Destruction-Efficiency Updates for 2026
1. California Air-District Rulemaking Remains Active
South Coast AQMD’s 2026 regulatory activity includes multiple initiatives affecting VOC-emitting industries and pollution-control requirements. Its current rulemaking pages show active work involving aerospace assembly, wood-product coatings, marine and pleasure-craft coatings, and consumer paint thinners and multipurpose solvents.
This is important because VOC compliance is not static. A facility that designed its emissions-control strategy several years ago may need to reassess whether its current processes, materials, control equipment, testing frequency, and documentation continue to satisfy applicable requirements.
The South Coast AQMD 2026 compliance calendar also includes new or updated deadlines affecting VOC-related operations. For example, Rule 1173 requirements beginning January 1, 2026 require certain petroleum and chemical facilities to expand component monitoring using Optical Gas Imaging (OGI) and maintain specified VOC leak thresholds. The same calendar identifies other 2026 control requirements involving captured fugitive emissions and air-pollution-control systems.
2. Rule 1124 Was Amended in April 2026
One significant 2026 development is the amendment of South Coast AQMD Rule 1124 — Aerospace Assembly and Component Manufacturing Operations, which was amended on April 3, 2026.
The rulemaking process examined control options for VOCs and toxic air contaminants associated with aerospace coating operations.
The March 2026 South Coast AQMD staff report evaluated thermal oxidizers and noted that they can achieve destruction efficiencies exceeding 98% when properly designed and operated. The report identifies temperature, residence time, and turbulence/mixing as important thermal-oxidizer design factors.
But the same analysis also identified an important disadvantage: thermal oxidation of certain chlorinated and fluorinated compounds can generate hydrochloric acid (HCl) and hydrofluoric acid (HF). Additional scrubber controls may therefore be necessary, increasing system complexity and operating costs.
What does this mean for industry?
The lesson is bigger than a single rule.
High VOC destruction efficiency does not automatically mean a control technology is appropriate for every chemical stream.
Facilities need to evaluate the complete emissions profile.
3. Thermal Oxidizers Remain an Important VOC-Control Technology
Thermal oxidizers continue to be used for controlling VOC and certain toxic-air-contaminant emissions. South Coast AQMD’s 2026 technical analysis describes thermal oxidizers as combustion devices that convert applicable organic pollutants primarily into carbon dioxide and water, while identifying temperature, residence time, and mixing as key performance factors.
The technology can provide very high VOC destruction efficiency under appropriate conditions.
However, performance depends on how the system is operated. Changes in VOC concentration, gas flow, process chemistry, temperature, residence time, mixing, equipment condition, and operating cycles can affect performance.
That is why source testing remains an important tool for demonstrating actual performance rather than relying solely on equipment design specifications.
4. California Regulators Are Looking at More Than VOCs
Another important 2026 compliance issue is that destroying VOCs does not mean the control system has no other emissions.
South Coast AQMD’s emissions-reporting guidance explains that thermal oxidation can result in emissions of NOx, SOx, CO, particulate matter, and toxic air contaminants in addition to the controlled VOC emissions. The agency encourages operators to use test results when calculating and reporting these emissions.
This creates a broader compliance challenge.
A facility may achieve excellent VOC destruction efficiency while still needing to address combustion-related emissions.
The right question is not simply:
“How efficiently are we destroying VOCs?”
It is:
“What is our complete emissions profile after the control device operates?”
5. EPA Continues to Emphasize Performance Monitoring
The U.S. EPA’s Compliance Assurance Monitoring guidance for thermal oxidizers demonstrates the importance of connecting performance testing with ongoing monitoring. The EPA’s technical guidance uses real facility case studies involving control-device parameters, long-term monitoring data, and performance/compliance testing. The guidance was updated July 2, 2026.
This reinforces an important compliance principle:
A source test provides a performance snapshot; continuous or periodic monitoring helps demonstrate that operating conditions remain consistent with the conditions under which compliance was established.
For facilities, this means testing and monitoring should work together rather than being treated as completely separate activities.
Why Is VOC Destruction Efficiency Testing Important?
Imagine purchasing an expensive industrial control system that is advertised as capable of destroying 99% of VOCs.
Then production conditions change.
The VOC concentration increases. The process begins operating intermittently. A valve develops leakage. Ceramic media becomes fouled. Temperature drops below the expected range. The process gas flow changes.
Does the system still achieve 99%?
That’s exactly why testing matters.
A manufacturer’s performance specification describes what equipment may achieve under defined conditions. A properly designed compliance test provides evidence of what the system is actually achieving under specified operating conditions.
Key Factors That Affect VOC Destruction Efficiency
Temperature
Thermal oxidation requires sufficient temperature for the targeted organic compounds to oxidize effectively. The appropriate temperature depends on the process, pollutant characteristics, equipment design, and applicable permit requirements.
South Coast AQMD identifies temperature as one of the fundamental design factors affecting thermal-oxidizer performance.
Residence Time
The gas must remain in the appropriate combustion environment long enough for the oxidation reaction to occur.
Insufficient residence time can reduce destruction performance.
Turbulence and Mixing
Effective mixing allows the VOC-containing process gas to interact properly with the combustion environment.
Poor mixing can create localized conditions where oxidation is less complete.
VOC Concentration
A control device may behave differently at low, moderate, or high VOC loading.
This is particularly important when production processes are intermittent or have large concentration swings.
Equipment Condition
Burners, valves, seals, fans, ceramic media, dampers, temperature sensors, controls, and ductwork can influence performance.
Capture Efficiency
There is another crucial issue:
The control device cannot destroy VOC emissions that never reach it.
A facility can therefore have excellent destruction efficiency at the oxidizer while still experiencing uncontrolled emissions because of poor capture or fugitive releases.
Pros of VOC Destruction Efficiency Testing
1. Demonstrates Actual Control Performance
Testing provides measurable evidence of control-device performance rather than relying solely on theoretical or manufacturer claims.
2. Supports Permit Compliance
Where required, source-test results can demonstrate compliance with applicable destruction-efficiency or outlet-emission requirements.
3. Helps Identify Problems Early
Testing may reveal declining control performance before the facility experiences a more serious compliance issue.
4. Provides Site-Specific Data
South Coast AQMD specifically recognizes site-specific destruction-efficiency test results as an important source of information for certain emissions calculations.
5. Supports Permit Renewals and Modifications
Reliable testing data can strengthen technical documentation for certain permit-related activities.
6. Helps Optimize Operations
Test results can show how temperature, process loading, production conditions, and other operating variables affect emissions-control performance.
7. Strengthens Environmental Reporting
Accurate data can improve emissions inventories and regulatory reporting.
Cons & Challenges of VOC Destruction Efficiency Testing
Testing Can Be Expensive
Professional source testing requires specialized equipment, experienced personnel, calibration, field labor, analytical work, and technical reporting.
Production Scheduling Can Be Difficult
Testing often needs to occur under representative operating conditions. Coordinating a source test with production schedules can therefore be challenging.
VOC Streams Can Be Variable
Intermittent processes, batch operations, changing solvents, changing production rates, and different raw materials can make representative testing more complicated.
Sampling Can Be Technically Complex
Accurate destruction-efficiency testing may require simultaneous inlet and outlet measurements, flow measurements, oxygen or carbon-dioxide measurements, moisture measurements, and detailed operating-condition documentation.
High Destruction Efficiency Can Have Tradeoffs
Thermal oxidation can create secondary pollutants such as NOx, CO, particulate matter, SOx, and potentially toxic or acidic combustion products depending on the process chemistry.
Regulatory Requirements Can Change
A testing program that was appropriate several years ago may need review as applicable rules, permits, source categories, and Air District policies evolve.
VOC Destruction Efficiency vs. Capture Efficiency
These terms are often confused.
Measurement
What It Means
Capture Efficiency
How much of the process-generated VOC is captured and routed to the control device
Destruction Efficiency
How much of the captured VOC is destroyed by the control device
Removal Efficiency
How much pollutant is removed from the treated stream, depending on the control technology
Overall Control Efficiency
The combined effect of capture and control/destruction
This distinction matters because a facility can have a 99% efficient oxidizer but still release VOCs if only part of the process emissions are captured.
How VOC Destruction Efficiency Testing Is Typically Conducted
A professional testing project generally begins with permit and regulatory review.
The testing team identifies the required pollutants, limits, methods, operating conditions, testing frequency, and reporting requirements.
A compliance test protocol is then developed to establish the sampling locations, test methods, number of runs, operating conditions, QA/QC requirements, calculations, and reporting format.
During testing, the team may measure VOC concentrations at the control-device inlet and outlet while simultaneously documenting operating parameters.
Depending on the applicable method and permit, testing may also involve:
Gas flow
Moisture
Oxygen
Carbon dioxide
Temperature
Fuel consumption
Production rate
VOC loading
Control-device operating parameters
The resulting data are evaluated and used to calculate the applicable destruction/control efficiency.
The final report should clearly document what was tested, how it was tested, under what operating conditions, what the results were, and whether the applicable compliance requirement was met.
What EES Can Test
Energy Environmental Solutions, Inc. (EES) supports facilities with a broad range of emissions-control testing services.
VOC Destruction Efficiency Testing
Evaluation of VOC inlet/outlet concentrations and applicable control efficiency.
RTO Testing
Testing of Regenerative Thermal Oxidizers, including VOC, NOx, CO, and applicable operating parameters.
Thermal Oxidizer Testing
Performance testing for thermal oxidation systems according to applicable requirements.
Source & Stack Testing
Field testing using applicable EPA, CARB, and local Air District methods.
NOx & CO Testing
Evaluation of combustion-related emissions where required.
CEMS / RATA / CGA
Support for continuous emissions monitoring systems and associated certification, relative accuracy testing, and calibration requirements.
Compliance Test Protocol Development
Preparation of testing protocols covering sampling, methods, QA/QC, operating conditions, calculations, and reporting.
Engineering Studies
Technical evaluations of emissions-control systems, operating conditions, and potential compliance strategies.
Regulatory Reporting
Preparation of organized technical reports and supporting documentation for regulatory compliance.
Industries That May Need VOC Destruction Efficiency Testing
Depending on their permit and emissions-control configuration, EES can support facilities in industries such as:
Aerospace Manufacturing
Chemical Manufacturing
Petroleum & Refining
Pharmaceutical Manufacturing
Paint & Coating
Metal Coating
Printing
Food Processing
Composite Manufacturing
Waste Treatment
Solvent-Using Operations
Industrial Manufacturing
Fuel Processing
Petroleum Storage and Loading
Other VOC-emitting industrial operations
The applicable testing requirement is facility-specific.
Why Choose EES for VOC Destruction Efficiency Testing?
When an Air District asks:
“How do you know your control device is achieving the required VOC destruction efficiency?”
The answer should be supported by credible technical data.
EES helps facilities build that evidence through:
VOC Destruction Efficiency Testing
RTO Testing
Thermal Oxidizer Testing
VOC Source Testing
Stack Testing
NOx Testing
CO Testing
CEMS
RATA
CGA
Compliance Test Protocol Development
Engineering Studies
QA/QC
Emissions Calculations
Regulatory Reporting
The goal is simple:
Measure it. Verify it. Document it. Stay compliant.
2026 Compliance Checklist for California Facilities
Before your next VOC compliance test, review:
Your current Air District permit
Applicable VOC rules
Required destruction/control efficiency
Required test frequency
Approved test methods
Sampling locations
Required operating conditions
Production rate during testing
VOC inlet concentration
VOC outlet concentration
Control-device temperature
Flow and moisture requirements
NOx/CO requirements
QA/QC requirements
Reporting deadlines
Continuous-monitoring requirements
Don’t assume that an old source-test protocol automatically remains appropriate.
Review the current requirements before scheduling the test.
The Big 2026 Takeaway
California’s 2026 regulatory activity demonstrates that VOC compliance continues to evolve across multiple industrial sectors. South Coast AQMD has active rulemaking involving aerospace, coatings, solvents, and other VOC-emitting operations, while its current emissions guidance emphasizes the importance of site-specific destruction-efficiency data for applicable thermal-oxidation calculations.
At the same time, regulators and technical guidance continue to emphasize that control-device performance depends on real operating conditions.
A number on a manufacturer’s brochure is not a substitute for a properly conducted compliance demonstration when testing is required.
Is your VOC control device really achieving the efficiency required by your permit?
Are your inlet and outlet measurements defensible?
Are your operating conditions properly documented?
Has your test protocol been reviewed against current requirements?
Are you prepared for your next Air District inspection?
If you are uncertain about any of these questions, a proactive compliance review can help identify potential issues before they become costly problems.
Need VOC Destruction Efficiency Testing in California?
Energy Environmental Solutions, Inc. (EES) helps industrial facilities evaluate and document the performance of VOC control systems.
Destruction Efficiency in California 2026: Latest Updates, Pros, Cons & How EES Helps Industries Stay Compliant
Destruction efficiency is becoming an increasingly important performance metric for California facilities that use thermal oxidizers, regenerative thermal oxidizers (RTOs), flares, vapor-control systems, and other air-pollution control equipment to reduce VOC and other organic emissions.
In simple terms, destruction efficiency measures how much of a pollutant entering a control device is actually destroyed before the treated gas is released. A commonly used calculation is:
But achieving a high percentage during one test is not necessarily the same as maintaining compliant performance during everyday operation.
California’s 2026 regulatory environment continues to emphasize emission reductions, monitoring, source testing, toxic-air-contaminant controls, and reliable emissions data. South Coast AQMD’s 2026 rule calendar contains more than two dozen planned rule amendments and adoptions addressing particulate matter, toxic air contaminants, monitoring, New Source Review, and other air-quality objectives.
For facilities using thermal oxidation or other control technologies, that creates a growing need for accurate destruction-efficiency testing and defensible compliance documentation.
Energy Environmental Solutions, Inc. (EES) helps industries with Destruction Efficiency Testing, VOC Testing, RTO Testing, Thermal Oxidizer Testing, Source & Stack Testing, CEMS, RATA, CGA, Compliance Test Protocol Development, Engineering Studies, QA/QC, and Regulatory Reporting.
What Is Destruction Efficiency?
Destruction efficiency, often called Destruction Removal Efficiency (DRE), describes the percentage of a pollutant that a control device removes through destruction.
For example, if a control device receives 100 pounds of VOCs and only 1 pound remains in the outlet gas, the calculated destruction efficiency would be approximately 99%.
This measurement is particularly important for equipment such as:
Regenerative Thermal Oxidizers (RTOs)
Thermal oxidizers
Catalytic oxidizers
Afterburners
Flares
VOC control systems
Certain combustion-based control devices
However, destruction efficiency is not the same as capture efficiency.
A facility can have an excellent control device but still release pollutants if the process exhaust is not effectively captured and routed to the control equipment.
That is why compliance evaluations may need to consider capture efficiency + control/destruction efficiency + operating conditions + actual emissions.
Is Destruction Efficiency Testing Compulsory in California?
There is an important distinction.
California does not have one universal destruction-efficiency testing requirement that applies identically to every industrial facility.
Whether a facility must demonstrate destruction efficiency depends on factors including:
Facility location
Local Air District
Air permit
Applicable regulation
Source category
Pollutant
Control technology
Required control efficiency
Federal requirements
State requirements
Permit-specific testing conditions
A current South Coast AQMD emissions-reporting guideline specifically instructs facilities using thermal oxidation to use site-specific destruction-efficiency test results, the applicable permit, or the applicable rule limit when determining vapor-destruction efficiency.
This is an important compliance message:
Don’t assume your facility’s required destruction efficiency—verify it from the applicable permit and regulation.
Latest California Updates in 2026
1. California Continues Strengthening Air-Quality Controls
South Coast AQMD’s 2026 rulemaking program includes more than two dozen planned rule amendments and adoptions.
The agency’s priorities include:
PM reduction
Toxic-air-contaminant controls
Updated toxic-air-contaminant lists
New Source Review
Monitoring requirements
Community emission-reduction objectives
The agency says these activities support the 2016 and 2022 Air Quality Management Plans, 2024 PM Plan, federal and state air-quality standards, and AB 617 Community Emission Reduction Plans.
For facilities using VOC destruction systems, this reinforces the importance of having reliable performance data.
2. Thermal Oxidation Remains an Important Control Technology
South Coast AQMD continues to evaluate thermal oxidation as an emissions-control option.
A March 2026 South Coast AQMD staff report evaluating aerospace coating controls recognized that thermal oxidizers can technically achieve high destruction efficiencies for certain VOC and toxic compounds. However, the agency also identified limitations for some chlorinated and fluorinated compounds because thermal oxidation can produce HCl and HF, requiring additional controls such as scrubbers.
The lesson for industry is important:
A high destruction-efficiency percentage does not automatically mean a control technology is appropriate for every pollutant.
The entire emissions profile must be evaluated.
3. Regulators Are Looking Beyond a Single Performance Number
South Coast AQMD’s 2026 activities demonstrate a broader focus on monitoring, toxic air contaminants, particulate matter, and emissions data rather than relying on a single compliance measurement.
A control device may destroy VOCs while simultaneously generating other combustion-related pollutants.
South Coast AQMD’s emissions-reporting guidance specifically states that thermal oxidation can generate NOx, SOx, CO, PM, and toxic air contaminants, and encourages operators to use site-specific test results for emissions calculations when available.
Therefore, a strong testing program should evaluate the complete picture.
4. Real-World 2026 Cases Show Why Performance Verification Matters
In June 2026, South Coast AQMD hearing-board documents involving Chiquita Canyon included conditions requiring equipment modifications designed to maintain sufficient flare operation and methane content for destruction efficiency consistent with regulatory requirements.
Earlier 2026 correspondence from South Coast AQMD also discussed the relationship between operating conditions, temperature, equipment design, source-test results, and destruction efficiency at the facility.
Although this example involves landfill-gas combustion rather than a conventional industrial RTO, it illustrates a broader principle:
Regulators can require evidence that operating conditions actually support the required destruction performance.
Why Is Destruction Efficiency Testing Important?
A control device manufacturer’s guarantee may say 98%, 99%, or higher.
But what happens after the equipment has been installed?
What happens when:
VOC loading changes?
Production increases?
Temperature fluctuates?
Ceramic media becomes fouled?
Valves begin leaking?
Airflow changes?
Process chemistry changes?
The burner operates differently?
The capture system develops leaks?
That’s where compliance testing becomes valuable.
Testing converts assumptions into measurable evidence.
Key Factors Affecting Destruction Efficiency
Temperature
Thermal oxidation generally requires sufficient temperature for effective oxidation.
If the temperature falls outside the required operating range, destruction performance may decline.
Residence Time
The contaminated gas needs sufficient time in the appropriate combustion environment.
Insufficient residence time can reduce destruction performance.
Turbulence & Mixing
Effective mixing is essential to expose the pollutant-containing gas to the required oxidation conditions.
VOC Concentration
A control system can perform differently depending on the concentration and composition of the incoming VOC stream.
Equipment Condition
Valves, burners, seals, ceramic media, sensors, ductwork, fans, and controls can all affect system performance.
Capture Efficiency
Even a highly efficient RTO cannot destroy pollutants that never reach it.
This makes capture and destruction efficiency two different but interconnected compliance considerations.
Pros of Destruction Efficiency Testing
1. Demonstrates Control Performance
Testing provides measurable evidence of how effectively the control device is destroying pollutants.
2. Supports Regulatory Compliance
Where required by a permit or regulation, test results can support compliance demonstrations.
3. Identifies Problems Early
Testing may reveal declining control efficiency before the problem becomes a larger compliance issue.
4. Supports Permit Applications
Reliable test data can be useful for permit modifications, renewals, and engineering evaluations.
5. Provides Site-Specific Data
South Coast AQMD specifically encourages the use of site-specific destruction-efficiency test results where available for emissions calculations.
6. Improves Operational Understanding
Testing can help facility engineers understand how production conditions affect control-device performance.
Cons & Challenges of Destruction Efficiency Testing
Professional testing also has challenges.
Testing Costs
Specialized source-testing equipment, qualified personnel, laboratory analysis, and reporting can increase project costs.
Production Coordination
Testing may need to occur under representative operating conditions, requiring coordination with production.
Complex Sampling
Some control-efficiency tests require simultaneous measurements at the inlet and outlet.
Variable VOC Streams
Changing process chemistry can make it difficult to establish representative testing conditions.
Secondary Pollutants
Thermal oxidation can create additional pollutants such as NOx, CO, SOx, PM, and certain toxic or acidic compounds, depending on the material being treated.
Documentation Requirements
A technically correct test can still create compliance problems if the supporting protocol, calibration, operating-condition records, calculations, or report are incomplete.
Destruction Efficiency vs. Removal Efficiency vs. Capture Efficiency
These terms are often confused.
Term
What It Measures
Destruction Efficiency
Percentage of pollutant destroyed by the control device
Removal Efficiency
Percentage of pollutant removed from the treated stream; the exact meaning depends on the control process
Capture Efficiency
Percentage of process emissions successfully captured and routed to the control device
Overall Control Efficiency
Combined effect of capture and control/destruction
A facility should understand exactly which metric its permit or regulation requires.
How Destruction Efficiency Testing Is Typically Performed
A professional testing program can include:
1. Permit Review
Identify the required control efficiency, pollutants, test frequency, and applicable methods.
2. Test Protocol Development
Define sampling locations, methods, operating conditions, number of runs, QA/QC, and calculations.
3. Pre-Test Coordination
Coordinate production and control-device operation to establish representative conditions.
4. Equipment Calibration
Prepare and calibrate sampling and analytical equipment.
5. Inlet Testing
Measure the pollutant concentration entering the control device.
6. Outlet Testing
Measure the pollutant concentration leaving the control device.
7. Operating Data Collection
Document temperature, flow, fuel use, production rate, oxygen, pressure, and other applicable parameters.
8. Calculations
Calculate destruction/control efficiency and mass emissions using the applicable methodology.
9. QA/QC Review
Verify data quality, calibration information, field records, and laboratory results.
10. Final Reporting
Prepare a technically defensible report for the facility and regulatory agency when required.
How EES Helps Industries
Energy Environmental Solutions, Inc. (EES) provides comprehensive emissions-testing and environmental compliance services for California industries.
Destruction Efficiency Testing
EES helps facilities design and perform testing programs to determine whether applicable control devices are achieving required performance.
RTO Testing
For regenerative thermal oxidizers, EES can support:
VOC inlet testing
VOC outlet testing
VOC destruction/control efficiency
NOx testing
CO testing
Operating-condition verification
Thermal Oxidizer Testing
EES can evaluate thermal oxidizer performance according to applicable permit and regulatory requirements.
Source & Stack Testing
Professional source and stack testing using applicable EPA, CARB, and local Air District methods.
Compliance Test Protocol Development
EES develops protocols covering:
Test methods
Sampling locations
Operating conditions
Test runs
QA/QC
Calculations
Reporting
CEMS, RATA & CGA
EES also supports:
CEMS Certification | RATA | CGA | QA/QC | Monitoring
Engineering Studies
Engineering evaluations can help facilities understand emissions-control performance and identify potential improvement opportunities.
Compliance Reporting
EES provides organized technical documentation including field data, calculations, QA/QC records, operating information, and final test results.
Industries That May Need Destruction-Efficiency Testing
Depending on their control technology and permit requirements, EES can support facilities in industries such as:
Aerospace
Chemical Manufacturing
Petroleum & Refining
Pharmaceutical Manufacturing
Paint & Coating
Metal Finishing
Printing
Food Processing
Waste Treatment
Recycling
Composite Manufacturing
Fuel Processing
Solvent-Using Industries
Industrial Manufacturing
Why Choose EES?
When a regulator asks:
“How do you know your control device is achieving the required efficiency?”
A manufacturer’s brochure isn’t always enough.
You need credible, documented, site-specific evidence when your permit or regulation requires it.
The 2026 Compliance Message for California Industry
California’s 2026 regulatory activity shows that air-quality management is continuing to focus on emission reductions, monitoring, toxic-air contaminants, particulate matter, and community exposure.
At the same time, regulators continue to use site-specific data and permit conditions to evaluate whether emission-control equipment is achieving required performance. South Coast AQMD’s current emissions guidance specifically points to site-specific destruction-efficiency testing, permit requirements, or applicable rule limits when determining destruction efficiency for certain thermal-oxidation applications.
That makes proactive testing a smart compliance strategy.
Don’t wait until an underperforming control device becomes a regulatory problem.
Ask:
Is your VOC control efficiency still meeting your permit requirement?
Are your inlet and outlet measurements defensible?
Are your operating conditions properly documented?
Has your control device been tested under representative conditions?
Is your current test protocol aligned with your permit?
If you don’t know the answer, it may be time for a compliance review.
Need Destruction Efficiency Testing in California?
Energy Environmental Solutions, Inc. (EES) helps industrial facilities evaluate, document, and improve emissions-control performance.
RTO Testing in California (2026): Latest Updates, Pros, Cons & How EES Helps Industries Stay Compliant
California’s industrial air-quality requirements continue to evolve in 2026, making Regenerative Thermal Oxidizer (RTO) testing an important compliance consideration for facilities using RTOs to control VOCs and other air pollutants.
An RTO is a sophisticated air-pollution control device that uses ceramic heat-recovery media and high-temperature oxidation to destroy combustible pollutants. But installing an RTO does not automatically prove compliance. Facilities may need source testing, operating-condition verification, continuous monitoring, and documentation demonstrating that the system is achieving the performance required by its permit or applicable regulations.
Recent California regulatory activity reinforces this point. South Coast AQMD continues developing and updating rules involving VOC emissions, NOx, toxic air contaminants, particulate matter, monitoring, and New Source Review. Its 2026 work also includes proposed amendments affecting industrial combustion equipment and air-quality controls.
For facilities operating RTOs, this makes proactive testing and compliance planning increasingly valuable.
Energy Environmental Solutions, Inc. (EES) helps industries with RTO Testing, Thermal Oxidizer Testing, VOC Testing, Source & Stack Testing, NOx & CO Testing, CEMS, RATA, CGA, Compliance Test Protocol Development, Engineering Studies, and Regulatory Reporting.
Regenerative Thermal Oxidizer Testing
What Is RTO Testing?
RTO testing evaluates the performance and emissions of a Regenerative Thermal Oxidizer under specified operating conditions.
RTOs are commonly used to control VOC emissions from processes such as:
Coating and painting
Chemical manufacturing
Printing
Solvent-based operations
Aerospace manufacturing
Food and industrial processing
Pharmaceutical manufacturing
Petroleum operations
Waste treatment
Other VOC-generating industrial processes
An RTO generally uses ceramic heat-exchange media to recover heat from the oxidized exhaust and transfer that heat to incoming process gas. This can make the technology highly energy-efficient compared with some conventional thermal oxidizer configurations.
However, the RTO must operate correctly. Testing can help determine whether the system is meeting applicable VOC destruction/control requirements and whether combustion-related emissions such as NOx and CO remain within applicable limits.
Is RTO Testing Compulsory in California?
This is an important distinction.
RTO testing is not automatically compulsory for every facility in California simply because the facility owns an RTO.
Testing requirements depend on factors such as:
Facility location
Air District
Permit conditions
Applicable rules
Type of process
Pollutants being controlled
RTO design
Required control efficiency
Operating conditions
Federal requirements
State requirements
Testing provisions in the facility’s permit
For example, a current San Joaquin Valley Air Pollution Control District permit for a facility using an RTO requires source testing of NOx, VOC at the RTO inlet, VOC at the RTO outlet, and VOC control efficiency within 60 days of startup and annually thereafter. The permit also specifies EPA/ARB test methods, advance notification, an approved source-test plan, and reporting requirements.
This is why facilities should review their individual permit and applicable Air District requirements rather than assuming that one statewide testing schedule applies to every RTO.
Latest California RTO Updates in 2026
1. Air District Rulemaking Remains Active
South Coast AQMD’s 2026 rulemaking agenda shows substantial ongoing regulatory activity involving industrial emissions. Proposed amendments include rules covering NOx from industrial boilers and process heaters, toxic air contaminants, particulate matter, monitoring, reporting, recordkeeping, and New Source Review.
For RTO operators, this matters because an RTO can control VOC emissions while its combustion process may also affect other pollutants.
A compliance program therefore needs to consider the whole emission profile, not only VOC destruction efficiency.
2. South Coast AQMD Continues Evaluating Thermal Oxidizers
A March 2026 South Coast AQMD staff report evaluating controls for aerospace coating operations discusses thermal oxidizers as a technology capable of achieving high destruction efficiencies for applicable VOC and toxic compounds.
The report also highlights an important limitation: thermal oxidation of certain chlorinated and fluorinated compounds can generate HCl and HF, potentially requiring additional scrubbing equipment. South Coast AQMD concluded that thermal oxidation was not the most practical control option for most of the aerospace coating applications evaluated in that particular rulemaking.
What does this mean for RTO operators?
The best control strategy depends on the specific pollutants in the process stream. A high destruction efficiency for VOCs does not necessarily mean the technology is optimal for every chemical mixture.
3. RTOs Remain an Established VOC Control Technology
South Coast AQMD’s BACT materials continue to recognize thermal oxidizers, including RTOs, as established control technologies for certain applications. The District’s BACT records include a regenerative thermal oxidizer determination for a metal-coating operation.
The District has also historically identified RTOs as BACT for certain VOC-control applications.
This means RTO technology remains relevant—but the required performance level is application-specific.
4. RTOs Can Have Strict Operating Conditions
A recent Valley Air District permit provides a useful real-world example.
The permit requires the RTO to operate with:
Minimum combustion-chamber temperature of 1,400°F
Minimum retention time of 0.5 seconds
Continuous temperature monitoring
Annual source testing
Approved testing methods
Advance notification
An approved source-test plan
Regulatory reporting
The permit also establishes pollutant-specific emission limits and requires testing of VOC control efficiency.
This illustrates why RTO testing is more than collecting a stack sample. Operating conditions and documentation can be just as important.
What Does RTO Testing Typically Measure?
Depending on the applicable permit and test protocol, an RTO testing program may evaluate:
The actual parameters and methods should be established from the applicable permit, Air District requirements, and approved test protocol.
How RTO Testing Works
A typical compliance project may involve several stages.
1. Permit Review
The testing team first reviews the facility’s permit and applicable regulatory requirements.
2. Test Protocol Development
A detailed protocol identifies sampling locations, methods, operating conditions, test runs, QA/QC requirements, and calculations.
3. Pre-Test Coordination
Testing is scheduled around representative production conditions.
4. Equipment Calibration
Sampling and measurement equipment is checked and calibrated according to applicable requirements.
5. Inlet & Outlet Testing
Where control efficiency is required, pollutant concentrations may be measured before and after the RTO.
6. Operating-Condition Documentation
Important parameters such as temperature, flow, production rate, fuel use, and process conditions may be documented.
7. QA/QC Review
Field and laboratory data are reviewed for completeness and technical validity.
8. Emissions Calculations
Results are converted into the units required by the applicable permit or rule.
9. Final Report
A comprehensive technical report is prepared for the facility and, when required, submitted to the applicable Air District.
Pros of RTO Testing
1. Demonstrates Compliance
Professional testing can provide documented evidence that an RTO is meeting applicable permit requirements.
2. Verifies VOC Control Efficiency
Testing can determine whether the RTO is achieving the required VOC destruction or control efficiency.
3. Identifies Equipment Problems
Testing may reveal issues involving:
Burner performance
Temperature control
Valve operation
Heat-recovery media
Airflow
Process loading
Combustion conditions
Early identification can allow operators to address problems before they become larger compliance concerns.
4. Supports Permit Requirements
Testing documentation can support:
Permit renewals
Permit modifications
Initial startup compliance
Periodic compliance demonstrations
Regulatory inspections
5. Improves Emissions Data
Site-specific test results can provide stronger emissions information than relying exclusively on generic assumptions or emission factors.
6. Supports Environmental Performance
An appropriately designed and operated RTO can substantially reduce VOC emissions from applicable industrial processes.
Cons & Challenges of RTO Testing
RTO testing also presents practical challenges.
Cost
Professional source testing requires specialized equipment, trained personnel, field time, laboratory analysis where applicable, and technical reporting.
Production Coordination
Testing often needs representative production conditions. Facilities may therefore need to coordinate testing with production schedules.
Complex Sampling
Measuring VOC concentrations and calculating control efficiency can require simultaneous inlet/outlet measurements and careful process documentation.
Operating Conditions Matter
A test performed under non-representative conditions may not provide a meaningful picture of normal performance and may not satisfy the applicable permit requirements.
Combustion Emissions
An RTO destroys VOCs through combustion, but the process can generate NOx, CO and other combustion-related emissions depending on the fuel, temperature, process gas, and equipment design.
Maintenance Requirements
RTOs contain valves, ceramic media, burners, controls, sensors, blowers, and other components that require appropriate maintenance.
Changing Regulations
California’s regulatory framework continues to change. Facilities need to periodically verify whether their existing testing program remains aligned with current permit and Air District requirements.
RTO Testing vs. Thermal Oxidizer Testing
The terms are related but not identical.
Thermal oxidizer testing is a broad term covering different thermal oxidation technologies.
RTO testing specifically refers to Regenerative Thermal Oxidizers.
An RTO uses regenerative heat recovery, typically through ceramic media and alternating flow paths, to improve energy efficiency.
Therefore, an RTO testing program may have additional operating considerations related to:
Regenerative chambers
Ceramic heat-exchange media
Valve switching
Purge cycles
Temperature profiles
Flow direction
Heat recovery
Pressure balance
Why RTO Testing Is Becoming More Important
California’s regulatory environment is moving toward greater emphasis on emissions reductions, monitoring, documentation, and control technology performance.
South Coast AQMD’s 2026 rulemaking activity includes proposed requirements addressing NOx, toxic air contaminants, particulate matter, monitoring, reporting, and New Source Review.
At the same time, real-world permits demonstrate that RTOs can be subject to detailed requirements for:
