Rule 1110.2 Compliance in California: Stationary Engine Testing, NOx, CO & VOC Requirements
Is your stationary engine compliant with California’s air-quality requirements?
If your facility operates a gaseous- or liquid-fueled stationary engine in the South Coast Air Quality Management District (South Coast AQMD), Rule 1110.2 may apply to your equipment.
The rule is designed to reduce NOx, VOC and CO emissions from regulated engines. The current South Coast AQMD rule was amended on November 3, 2023, and South Coast AQMD currently lists Proposed Amended Rule 1110.2 (PAR 1110.2) among rules in the proposal/amendment process.
For facility owners, plant managers and EHS professionals, this means engine testing, monitoring, recordkeeping and compliance planning should not be treated as an afterthought.
Rule 1110.2 California
What Is South Coast AQMD Rule 1110.2?
Rule 1110.2 – Emissions from Gaseous- and Liquid-Fueled Engines establishes emission and monitoring requirements for applicable engines.
The current rule states that its purpose is to reduce:
- NOx — Nitrogen Oxides
- VOC — Volatile Organic Compounds
- CO — Carbon Monoxide
The rule generally applies to stationary and portable engines over 50 rated brake horsepower (bhp), subject to its applicability provisions and exemptions.
Important California compliance point
Rule 1110.2 is not a single statewide California rule. It is a South Coast AQMD rule, so facilities outside the South Coast AQMD jurisdiction must determine which local air-district requirements apply.
Why Rule 1110.2 Matters to Your Business
Stationary internal-combustion engines are used throughout California industry for:
- Power generation
- Natural-gas compression
- Cogeneration
- Industrial processes
- Water and wastewater operations
- Agricultural operations
- Emergency/standby power
- Other mechanical and electrical applications
Depending on the engine and operating conditions, emissions can include significant amounts of NOx, CO and VOCs.
That’s why regulatory agencies require facilities to demonstrate that applicable engines are operating within their permitted and regulatory limits.
Which Engines Can Be Subject to Rule 1110.2?
Potentially regulated equipment can include:
Natural Gas Engines
Used for generators, compressors, pumps and industrial equipment.
Biogas Engines
Engines operating on landfill gas or digester gas can have specific requirements.
Liquid-Fueled Engines
Certain stationary engines using liquid fuels may fall under the rule.
Large Industrial Engines
Large engines can trigger more extensive monitoring requirements.
Low-Use Engines
The rule contains specific provisions for engines operating less than 500 hours/year or using less than 1 × 10⁹ Btu/year of fuel, subject to the applicable requirements.
2026 Regulatory Update: Rule 1110.2 Remains Under Amendment Review
One of the most important things facility operators should know in 2026 is that South Coast AQMD currently lists Proposed Amended Rule 1110.2 as an active rulemaking item.
The PAR 1110.2 process was developed alongside proposed Rule 1110.3 for linear generators. South Coast AQMD’s rulemaking page contains draft documents and working-group materials from the process.
What does this mean for industry?
It means businesses should monitor regulatory developments rather than relying only on an old compliance checklist.
However, a proposed amendment should not be treated as an adopted requirement until officially adopted and effective.
2026 strategy:
Know today’s requirements + monitor tomorrow’s requirements.
Rule 1110.2 Emission Testing: What Is Tested?
Depending on the applicable engine category and compliance requirement, testing can involve:
NOx Testing
NOx is one of the primary pollutants regulated under Rule 1110.2.
CO Testing
Carbon monoxide provides important information about combustion performance and compliance.
VOC Testing
VOC emissions are also regulated, with applicable limits depending on the engine category.
South Coast AQMD maintains a specific source-test protocol for NOx, CO and VOC testing for stationary internal-combustion engines subject to Rule 1110.2.
Why Professional Engine Emissions Testing Matters
A stationary engine may appear to operate normally while still producing emissions above an applicable limit.
For example:
Engine running normally
↓
Combustion conditions change
↓
NOx/CO/VOC emissions increase
↓
Compliance test fails
↓
Corrective action + retesting
This is why proactive emissions testing can be valuable.
Rule 1110.2 Source Testing Requirements
For applicable source testing, the rule contains detailed requirements.
Among other provisions, applicable testing can require testing during:
- Normal operation
- Actual duty cycle
- Peak load
- Minimum practical load
The rule states that certain source testing must include at least 30 minutes during normal operation, plus NOx and CO testing at applicable peak and minimum loads, unless the permit limits operation to a defined load range.
Another important requirement:
The rule states that testing should occur at least 40 operating hours or one week after engine servicing or tuning, as applicable. It also prohibits pre-tests for compliance.
That means testing schedules need to be planned carefully.
Source-Test Protocol: Don’t Leave It Until the Last Minute
One of the biggest compliance mistakes is treating the source-test protocol as paperwork to complete immediately before testing.
Rule 1110.2 requires, for applicable tests, submission of a source-test protocol for written approval at least 60 days before the scheduled test date. The protocol must address items such as:
- Engine identification
- Permit/application information
- Applicable emission limits
- Test methods
- Number of test runs
- Operating loads
- VOC sampling requirements
- Parameters measured under the Inspection & Monitoring Plan
The rule also requires approval before testing.
That’s why early planning matters.
Protocol → Approval → Testing → Reporting
Testing Contractor Requirements
For applicable Rule 1110.2 source tests, the rule requires use of a contractor approved by the Executive Officer under the Laboratory Approval Program (LAP) for the necessary test methods.
South Coast AQMD also maintains its source-testing methods and procedures, including the dedicated Rule 1110.2 protocol.
Before hiring a testing company, verify:
- Appropriate test-method approval
- Relevant experience
- Qualified personnel
- Proper instrumentation
- QA/QC procedures
- Reporting capability
- Familiarity with South Coast AQMD requirements
Source-Test Reporting
Testing doesn’t end when the instruments are removed from the stack.
For applicable Rule 1110.2 testing, the rule requires source-test reports to be submitted to the Executive Officer within 60 days of completion of the test.
A professional testing program therefore includes:
Planning → Field Testing → Data Validation → Calculations → Report Preparation → Submission
CEMS Requirements Under Rule 1110.2
Large engines may have additional continuous monitoring requirements.
The current rule requires NOx and CO CEMS for certain engines rated 1,000 bhp or greater and operating more than 2 million bhp-hours per calendar year.
CEMS can also be required at facilities with applicable engines having a combined rating of 1,500 bhp or greater at the same location and combined fuel usage exceeding 16 × 10⁹ Btu/year, subject to the rule’s provisions and exclusions.
The rule also requires applicable CEMS to comply with relevant requirements under Rules 218 and 218.1, including equipment specifications, certification, operation, recordkeeping, QA and reporting.
This connects Rule 1110.2 directly with CEMS compliance.
If your engine requires CEMS, you may also need:
CEMS Certification + QA/QC + RATA/other applicable performance testing + Data Validation
Inspection & Monitoring Plans
Not every facility uses CEMS for every engine.
Rule 1110.2 also contains Inspection and Monitoring (I&M) requirements.
Applicable operators may need an approved I&M Plan covering items specified by the rule.
South Coast AQMD also provides:
- Combustion Gas Periodic Monitoring Protocol
- Calibration recordkeeping forms
- Periodic monitoring forms
- Stability-check forms
- Linearity/interference records
through its Rule 1110.2 compliance resources.
Portable Analyzer Testing
Portable combustion analyzers can play an important role in Rule 1110.2 compliance.
South Coast AQMD states that portable-analyzer engine tests required under the I&M provisions must be conducted by a person who has completed an approved training program and received South Coast AQMD certification.
This is important because a portable-analyzer measurement is not simply a matter of taking a reading.
Proper procedure matters.
The person conducting the test needs appropriate training, equipment, calibration and documentation.
Emergency Standby Engines: A Common Compliance Misunderstanding
Many businesses assume:
“It’s an emergency generator, so air-quality rules don’t apply.”
That’s not necessarily correct.
South Coast AQMD identifies an emergency backup generator as a standby ICE or turbine for non-utility power generation that operates no more than 200 hours per year and is used for emergency power failure or routine testing/maintenance, subject to the applicable requirements.
Rule 1110.2 also contains exemptions for certain emergency standby engines limited by permit conditions to 200 hours or less per year, along with other specified categories.
The permit condition matters.
Don’t assume that simply calling an engine an “emergency generator” automatically exempts it from every requirement.
Rule 1110.2 service provider in California
Rule 1110.2 Compliance: Pros & Cons
Advantages of Proactive Compliance
1. Early Problem Detection
Testing can identify elevated emissions before a regulatory deadline.
2. Better Engine Performance
Combustion testing can identify operating problems.
3. Reduced Compliance Risk
Regular monitoring provides better visibility into emissions.
4. Better Documentation
Professional reports create an organized compliance record.
5. Improved Maintenance Planning
Emission trends can help identify equipment problems.
6. Better Preparation for Rule Changes
Facilities that maintain accurate emissions data can make better upgrade decisions.
Potential Challenges
Testing Costs
Professional source testing requires equipment, personnel and laboratory/analytical resources.
Operational Coordination
The engine may need to operate at specific loads during testing.
Protocol Lead Time
Applicable protocols may need regulatory approval well before testing.
Failed Tests
An exceedance can require corrective action and potentially additional testing.
CEMS Costs
Large applicable engines may require continuous monitoring systems.
Recordkeeping
Compliance requires maintaining appropriate records and documentation.
What Happens If an Engine Fails?
A failed test shouldn’t be ignored.
A typical corrective approach is:
1. Identify the Cause
Check:
- Fuel system
- Air/fuel ratio
- Ignition
- Engine condition
- Catalyst
- Control equipment
- Operating load
- Maintenance history
2. Correct the Problem
Tune, repair or modify the equipment as appropriate.
3. Verify Performance
Conduct appropriate testing or monitoring.
4. Document the Corrective Action
Maintain records of:
- Problem
- Corrective action
- Test results
- Maintenance
- Retesting
5. Report When Required
Meet applicable regulatory reporting requirements.
Industries That Can Benefit From Rule 1110.2 Compliance Services
Potential clients include:
Manufacturing
- Food processing
- Chemical plants
- Pharmaceutical facilities
- Metal manufacturing
- Industrial manufacturing
Energy & Power
- Distributed generation
- Cogeneration
- Power generation
- Utility-related operations
Oil & Gas
- Compressor stations
- Gas processing
- Petroleum operations
Water & Wastewater
- Wastewater treatment plants
- Water facilities
- Digester-gas engines
Agriculture
- Agricultural stationary engines
- Irrigation/pumping applications
Commercial & Institutional
- Large facilities
- Hospitals
- Universities
- Commercial operations
The exact applicability must be determined from the engine, permit, fuel, operating conditions and applicable South Coast AQMD provisions.
How EES Can Help With Rule 1110.2 Compliance
Energy Environmental Solutions, Inc. (EES) can support facilities with a coordinated engine-emissions compliance program.
1. Rule Applicability Review
EES can help evaluate:
Engine Type + Fuel + bhp + Operating Hours + Permit + Applicable Rule
2. Rule 1110.2 Emissions Testing
Testing can address applicable:
NOx + CO + VOC
requirements using the applicable approved methods and procedures.
South Coast AQMD publishes a dedicated Rule 1110.2 source-test protocol for these pollutants.
3. Source-Test Protocol Development
EES can help prepare a protocol covering:
- Engine identification
- Permit conditions
- Applicable limits
- Test methods
- Sampling duration
- Operating loads
- QA/QC
- Required monitoring parameters
4. Portable Analyzer Testing
Where applicable, EES can support combustion-gas periodic monitoring and required portable-analyzer testing through appropriately qualified personnel.
5. CEMS Compliance
For applicable large engines, EES can support:
- CEMS testing
- CEMS certification
- QA/QC
- RATA
- CGA
- Data evaluation
- Compliance documentation
6. Compliance Reporting
EES can assist with technical reporting and documentation following applicable testing.
7. Corrective-Action Support
If test results indicate an emissions problem, EES can help the facility understand the technical issue and plan appropriate corrective testing.
EES Rule 1110.2 Compliance Process
STEP 1 — ENGINE REVIEW
Fuel + bhp + operating hours + permit
↓
STEP 2 — RULE REVIEW
Rule 1110.2 + applicable provisions
↓
STEP 3 — TEST PLAN
Methods + loads + sampling + QA/QC
↓
STEP 4 — PROTOCOL
Prepare & submit applicable source-test protocol
↓
STEP 5 — FIELD TEST
NOx + CO + VOC
↓
STEP 6 — DATA ANALYSIS
Validate results against applicable limits
↓
STEP 7 — REPORT
Prepare compliance documentation
↓
STEP 8 — FOLLOW-UP
Corrective action / retesting if required
Why Choose EES?
Engine emissions testing is not simply:
“Put a meter on the engine and take a reading.”
A successful compliance program requires understanding:
Engine Technology + Combustion + Test Methods + Air-District Rules + QA/QC + Reporting
That’s where an experienced environmental testing partner can add value.
2026 Rule 1110.2 Compliance Checklist
Before your next engine test, ask:
- Is my engine subject to Rule 1110.2?
- What is the engine’s rated bhp?
- What fuel does it use?
- Is it stationary, portable or non-road?
- Is it an emergency standby engine?
- What are the permit operating-hour limits?
- What are the applicable NOx limits?
- What are the applicable CO limits?
- What are the applicable VOC limits?
- Is source testing required?
- Is portable-analyzer monitoring required?
- Is an I&M Plan required?
- Is CEMS required?
- Is CEMS certification current?
- Is a RATA or other QA/QC test due?
- Is the source-test protocol approved?
- Is the testing contractor appropriately approved?
- Are records current?
- Have applicable Rule 1110.2 amendments been reviewed?
Don’t Wait Until Your Engine Fails a Compliance Test
A compliance problem is much easier to manage when you know about it before the deadline.
EES Can Help You:
Review Rule 1110.2 applicability Develop test protocols Conduct NOx/CO/VOC testing Perform applicable portable-analyzer monitoring Support CEMS compliance Evaluate emissions results Prepare technical reports Support corrective-action planning
Your Engine Runs Every Day. Make Sure Your Compliance Program Does Too.
Energy Environmental Solutions, Inc. (EES)
Phone: 714-630-5210 | 714-630-7844
Email: info@sourcetester.com
Website: sourcetester.org