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.

Explore the latest 2026 Rule 1147.1 updates for California aggregate dryers, NOx and CO testing, pros, cons, compliance requirements and how EES helps industries.

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.

Compliance Test Protocol Development

EES can help prepare protocols covering:

Sampling → Methods → Operating Conditions → QA/QC → Calculations → Reporting

CEMS / RATA / CGA

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:

Measure Emissions. Verify Compliance. Protect Your Operations.

Energy Environmental Solutions, Inc. (EES)

Phone: 714-630-5210 | 714-630-7844
Email: info@sourcetester.com
Website: sourcetester.org

Rule 1147.1 California 2026 | Aggregate Dryer NOx Testing | Source Tester | EES