Nitrogen Oxides (NOx) Testing for CARB Compliance

At REM, our source testing protocols are designed to meet and exceed California Air Resources Board (CARB) requirements, including the accurate measurement of nitrogen oxides (NOx)—a critical pollutant regulated due to its role in smog formation and adverse health impacts.

What We Measure

NOx refers collectively to nitric oxide (NO) and nitrogen dioxide (NO₂), both of which are produced during high-temperature combustion processes. CARB regulations require precise quantification of these compounds to assess compliance with emissions limits and permitting conditions.

How REM Tests for NOx

REM utilizes industry-standard EPA reference methods and advanced instrumentation to ensure defensible, audit-ready data:

• EPA Method 7E (Instrumental Analyzer Procedure)
  Our primary approach for NOx measurement is EPA Method 7E, which uses a continuous emissions analyzer to quantify NO and NOx concentrations in real time.

• Chemiluminescence Detection (CLD)
  We deploy chemiluminescence analyzers—the gold standard for NOx measurement. This method works by reacting nitric oxide (NO) with ozone (O₃), producing light. The intensity of this light is directly proportional to the NO concentration.
  For total NOx measurement, nitrogen dioxide (NO₂) is first converted to NO using a thermal or catalytic converter, allowing total NOx to be measured accurately.

• In-Stack Sampling Procedures
  Our trained technicians extract gas samples directly from the emission source (e.g., stack or duct) using heated sample lines to prevent condensation and loss of nitrogen species. This ensures sample integrity from extraction to analysis.

• Calibration and Quality Assurance
  We perform multi-point calibrations using certified calibration gases before, during, and after testing. Zero and span checks are conducted to verify analyzer stability, and all procedures follow strict QA/QC protocols in accordance with EPA and CARB guidelines.

• Moisture and Oxygen Corrections
  Measured NOx concentrations are corrected for oxygen content and moisture levels to standardize results, ensuring accurate comparison against regulatory limits.

What Clients Receive

• Real-Time Data Monitoring during testing to ensure operational transparency

• Comprehensive Test Reports formatted to CARB specifications

• Emission Rates and Compliance Determinations clearly outlined

• Full Documentation of methods, calibrations, and QA/QC procedures for regulatory submittal

Why It Matters

Accurate NOx measurement is essential not only for regulatory compliance but also for operational insight. REM’s testing approach provides reliable data that clients can use to validate control technologies, optimize combustion efficiency, and confidently demonstrate compliance with CARB and local air district requirements.