§ 1065.277 - NH3 measurement devices.

§ 1065.277 NH₃ measurement devices.

(a) General component requirements. We recommend that you use an analyzer that meets the specifications in § 1065.205. Note that your system must meet the linearity verification in § 1065.307.

(b) Instrument types. You may use any of the following analyzers to measure NH₃:

(1) Nondispersive ultraviolet (NDUV) analyzer.

(2) Fourier transform infrared (FTIR) analyzer. Use appropriate analytical procedures for interpretation of infrared spectra. For example, EPA Test Method 320 (see § 1065.266(c)) and ASTM D6348 (incorporated by reference, see § 1065.1010) are considered valid methods for spectral interpretation.

(3) Laser infrared analyzer. Examples of laser infrared analyzers are pulsed-mode high-resolution narrow-band mid-infrared analyzers, modulated continuous wave high-resolution narrow band near and mid-infrared analyzers, and modulated continuous-wave high-resolution near-infrared analyzers. A quantum cascade laser, for example, can emit coherent light in the mid-infrared region where NH₃ and other nitrogen compounds can effectively absorb the laser's energy.

(c) Sampling system. Minimize NH₃ losses and sampling artifacts related to NH₃ adsorbing to surfaces by using sampling system components (sample lines, prefilters and valves) made of stainless steel or PTFE heated to (110 to 202) °C. If surface temperatures exceed ≥130 °C, take steps to prevent any DEF in the sample gas from thermally decomposing and hydrolyzing to form NH₃. Use a sample line that is as short as practical.

(d) Interference verification. Certain species can positively interfere with NDUV, FTIR, and laser infrared analyzers by causing a response similar to NH₃. Perform interference verification as follows:

(1) Perform SO₂ and H₂O interference verification for NDUV analyzers using the procedures of § 1065.372, replacing occurances of NO_X with NH₃. NDUV analyzers must have combined interference that is within (0.0 ±2.0) µmol/mol.

(2) Perform interference verification for FTIR and laser infrared analyzers using the procedures of § 1065.377. Use good engineering judgment to determine interference species. Note that interference species, with the exception of H₂O, are dependent on the NH₃ infrared absorption band chosen by the instrument manufacturer. Determine interference species under this paragraph (d)(2) that are appropriate for each NH₃ infrared absorption band, or you may identify the interference species based on the instrument manufacturer's recommendations.

[89 FR 29797, Apr. 22, 2024]