Ammonia (NH₃) Slip Testing for CARB Compliance

As part of our CARB-compliant source testing services, REM Environmental incorporates ammonia (NH₃) slip measurement to support facilities operating selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR) systems. Monitoring NH₃ slip is critical for demonstrating proper system performance, optimizing reagent usage, and ensuring compliance with evolving regulatory requirements.

What is NH₃ Slip?

NH₃ slip refers to unreacted ammonia passing through the emissions control system and being released in the exhaust stream. While ammonia is injected to reduce NOₓ emissions, incomplete reaction or over-injection can result in measurable NH₃ emissions. Excessive slip can contribute to secondary particulate formation, visible plumes, odor issues, and potential regulatory exceedances.

REM’s Measurement Approach

REM utilizes proven, CARB-accepted source test methodologies to quantify ammonia emissions with high accuracy and repeatability. Our approach is tailored to the specific process and control technology but generally includes:

• Isokinetic or extractive sampling techniques designed to capture representative flue gas conditions

• Use of impinger trains or sorbent-based collection systems to selectively capture ammonia from the gas stream

• Strict adherence to method-defined temperature control and moisture management to prevent ammonia loss or transformation during sampling

• Field quality controls including calibration checks, blanks, and duplicate runs to ensure data integrity

Depending on project requirements, REM may apply methodologies aligned with:

• Conditional Test Method (CTM-027 or equivalent) for ammonia

• ASTM D6348 (FTIR-based analysis) for real-time or integrated measurement

• Other CARB-approved or site-specific protocols

Analytical Process

Collected samples are analyzed using laboratory-based wet chemistry techniques or instrumental methods such as Fourier Transform Infrared Spectroscopy (FTIR). These methods allow for:

• Quantification of ammonia concentration (ppmvd or lb/hr)

• Correction to standard conditions (e.g., dry basis, reference oxygen content)

• Cross-verification with process and control system operating parameters

Quality Assurance and Data Integrity

REM follows a rigorous QA/QC framework consistent with CARB and EPA expectations:

• Pre- and post-test leak checks and calibration verification

• Chain-of-custody documentation for all samples

• Use of method blanks and spiked samples where applicable

• Data validation to confirm method compliance and defensibility

Why NH₃ Slip Testing Matters

Accurate measurement of ammonia slip provides actionable insight into system performance:

• Optimizes reagent injection rates, reducing operational costs

• Prevents ammonium salt formation that can foul downstream equipment

• Supports regulatory reporting and permit compliance

• Demonstrates environmental stewardship and operational control