EPA vs. CARB vs. SCAQMD Test Methods: Which Apply to Your Facility?

If you operate permitted equipment in Southern California, your facility is subject to emissions testing requirements from three separate regulatory bodies. Federal EPA methods, state CARB methods, and district-level SCAQMD methods can all apply to the same piece of equipment, sometimes simultaneously.

The question isn't which agency matters most. It's which specific test method your permit requires. Get it wrong, and you've spent money on a test that doesn't satisfy your compliance obligation.

Three Layers of Regulation, Three Sets of Methods

The regulatory structure works like a hierarchy. EPA sets the federal baseline. CARB layers state requirements on top. SCAQMD, as the local air quality management district for the South Coast Air Basin, adds its own district-specific methods and often imposes stricter standards than either EPA or CARB.

Each agency publishes its own set of test methods with distinct numbering systems, procedures, and QA/QC requirements. They are not interchangeable unless your permit explicitly says otherwise.

EPA Test Methods: The Federal Baseline

EPA methods are codified in 40 CFR Part 60, Appendix A. These are the methods most facilities and testing companies encounter first. They cover the fundamentals of stack emissions testing and serve as the reference standard nationwide.

Common EPA methods include:

• Method 1 -- Sample and velocity traverses for stationary sources
• Method 2 -- Determination of stack gas velocity and volumetric flow rate
• Method 5 -- Determination of particulate matter emissions
• Method 7E -- Determination of NOx emissions (instrumental)
• Method 10 -- Determination of CO emissions
• Method 25A -- Determination of total gaseous organic concentration (FID)
• Method 201A -- Determination of PM10 and PM2.5 emissions

If your facility is subject to a federal NSPS (New Source Performance Standard) or NESHAP (National Emission Standard for Hazardous Air Pollutants), EPA methods are what you'll follow. Many SCAQMD permits also reference EPA methods directly, particularly for RATA requirements on CEMS.

CARB Test Methods: California's State Layer

CARB maintains its own set of test methods that apply statewide. These methods address pollutants and situations that EPA methods either don't cover or don't address with the specificity California requires.

CARB methods are numbered sequentially and include several that have no EPA equivalent:

• CARB Method 425 -- Determination of hexavalent chromium emissions
• CARB Method 428 -- Determination of polychlorinated dibenzo-p-dioxins and dibenzofurans
• CARB Method 429 -- Determination of polycyclic aromatic hydrocarbon emissions
• CARB Method 430 -- Determination of formaldehyde and acetaldehyde emissions
• CARB Method 436 -- Determination of multiple metals emissions

These methods exist because California regulates toxic air contaminants more aggressively than the federal government. If your facility has an air toxics permit condition or is subject to the AB 2588 Hot Spots program, CARB methods are likely in play.

CARB also maintains the Independent Contractor program. Any testing company performing source tests for state regulatory purposes must be registered as an Independent Contractor with CARB. This is separate from SCAQMD's LAP program.

SCAQMD Test Methods: District-Level Requirements

SCAQMD publishes its own test methods, and these are the ones that trip up facilities most often. SCAQMD methods follow an X.1 numbering format that roughly corresponds to their EPA counterparts but with district-specific modifications.

Key SCAQMD methods include:

• Method 1.1 -- Sample and velocity traverses
• Method 5.1 -- Determination of particulate matter emissions
• Method 25.1 -- Determination of total gaseous non-methane organic compounds
• Method 100.1 -- Instrumental analyzer procedures (continuous analyzers)
• Method 207.1 -- Determination of NOx, CO, and O2 from stationary sources

Where SCAQMD Methods Differ

The differences between SCAQMD and EPA methods aren't cosmetic. SCAQMD Method 100.1, for example, governs the use of portable continuous analyzers for measuring NOx, CO, O2, and SO2. There is no direct EPA equivalent for this specific protocol. It dictates calibration procedures, data validation criteria, and reporting requirements unique to the South Coast district.

SCAQMD Method 5.1 parallels EPA Method 5 for particulate matter but includes district-specific sampling and analytical requirements. Method 207.1 covers instrumental measurement of NOx and CO in a manner tailored to SCAQMD's regulatory framework.

When your SCAQMD permit specifies an SCAQMD method, you must use that method. Substituting the EPA equivalent without written approval from SCAQMD is a compliance violation.

How to Determine Which Methods Apply to Your Equipment

The answer is in your permit. Every SCAQMD-permitted source has conditions that specify the test methods required for compliance demonstrations. Here's where to look:

Step 1: Review your permit conditions. Each piece of equipment listed on your SCAQMD permit will have associated testing requirements. These conditions name the specific methods by number.

Step 2: Check the applicable rule. Rules like 1146 (boilers), 1147 (NOx from miscellaneous sources), and 218.2 (continuous monitoring) reference specific test methods. The rule itself will tell you which methods are acceptable.

Step 3: Read the protocol. Before any source test, a test protocol must be prepared and submitted to SCAQMD. The protocol identifies the methods that will be used. SCAQMD reviews and approves or modifies the protocol before testing proceeds.

Common Equipment and Applicable Methods

Here's how methods typically apply to equipment found in SCAQMD-permitted facilities:

Boilers and heaters (Rules 1146/1146.1): SCAQMD Method 100.1 for NOx, CO, and O2. Some permits reference EPA Method 7E and Method 10 for NOx and CO respectively.

Turbines and engines (Rule 1134): SCAQMD Method 100.1 or EPA Method 7E/Method 10, depending on permit conditions. RATA requirements for CEMS typically reference EPA Methods 7E and 10.

Paint spray booths and coating operations (Rule 1107): EPA Method 25A or SCAQMD Method 25.1 for VOC. Particulate via EPA Method 5 or SCAQMD Method 5.1.

Chrome plating operations (Rule 1469): CARB Method 425 for hexavalent chromium. This is a CARB method, not EPA or SCAQMD, because California has specific hex chrome regulations.

Waste incinerators and combustion sources: CARB Method 428 for dioxins/furans, CARB Method 429 for PAHs. EPA Method 23 may also apply for federal requirements.

Metal melting and heat treating: CARB Method 436 for metals, EPA Method 29 for metals, SCAQMD Method 5.1 for particulate.

The LAP and Independent Contractor Programs

Your testing company's approvals matter as much as the methods themselves.

SCAQMD LAP (Laboratory Approval Program): Any company performing source tests for SCAQMD compliance must be approved under the LAP. This includes meeting QA/QC standards, participating in audits, and maintaining certified analysts. Accurate Environmental Services is SCAQMD LAP-approved.

CARB Independent Contractor: For state-level testing, particularly toxic air contaminant testing under AB 2588, the testing company must be registered as a CARB Independent Contractor. This is a separate credential from the LAP.

Using a testing company that lacks the appropriate approval means your test results may not be accepted by the agency. That puts your facility back at square one with deadlines ticking.

When Methods Overlap -- and When They Don't

Some pollutants can be measured by methods from multiple agencies. PM can be measured by EPA Method 5, SCAQMD Method 5.1, or EPA Method 201A. But your permit dictates which is acceptable.

Other situations have no overlap. SCAQMD Method 100.1 is district-specific. CARB Method 425 for hex chrome has no SCAQMD equivalent. EPA Method 23 for dioxins and CARB Method 428 differ in procedure despite similar scope.

The critical mistake is assuming any PM method satisfies a PM permit condition. Method selection is permit-driven, not pollutant-driven. Use the wrong method and SCAQMD can reject the results -- meaning you've paid for a test that doesn't count, and you still owe a compliant test within your deadline. A rejected test can trigger a Notice of Violation if the deadline passes without valid results.

The Bottom Line

Three agencies, three sets of methods. Your permit tells you which ones apply. Your testing company needs to be approved under the right program for the methods being run.

Don't guess. Review your permit conditions, work with a testing company that understands the SCAQMD, CARB, and EPA frameworks, and make sure the test protocol is approved before anyone shows up with sampling equipment.

Frequently Asked Questions