Code of Federal Regulations Title 40. Protection of Environment § 40.1065.266 Fourier transform infrared analyzer

(a) Application. For engines that run only on natural gas, you may use a Fourier transform infrared (FTIR) analyzer to measure nonmethane hydrocarbon (NMHC) and nonmethane-nonethane hydrocarbon (NMNEHC) for continuous sampling. You may use an FTIR analyzer with any gaseous-fueled engine, including dual-fuel and flexible-fuel engines, to measure CH₄ and C₂ H₆, for either batch or continuous sampling (for subtraction from THC).

(b) Component requirements. We recommend that you use an FTIR analyzer that meets the specifications in Table 1 of § 1065.205. Note that your FTIR–based system must meet the linearity verification in § 1065.307. Use appropriate analytical procedures for interpretation of infrared spectra. For example, EPA Test Method 320 (see https://www.epa.gov/emc/method–320–vapor-phase-organic-and-inorganic-emissions-extractive-ftir) and ASTM D6348 (incorporated by reference in § 1065.1010) are considered valid methods for spectral interpretation. You must use heated FTIR analyzers that maintain all surfaces that are exposed to emissions at a temperature of (110 to 202) °C.

(c) Hydrocarbon species for NMHC and NMNEHC additive determination. To determine NMNEHC, measure ethene, ethyne, propane, propene, butane, formaldehyde, acetaldehyde, formic acid, and methanol. To determine NMHC, measure ethane in addition to those same hydrocarbon species. Determine NMHC and NMNEHC as described in § 1065.660(b)(4) and § 1065.660(c)(3).

(d) NMHC and NMNEHC CH₄ and C₂H₆ determination from subtraction of CH₄ and C₂H₆ from THC. Determine CH₄ as described in § 1065.660(d)(2) and C₂H₆ as described § 1065.660(e). Determine NMHC from subtraction of CH₄ from THC as described in § 1065.660(b)(3) and NMNEHC from subtraction of CH₄ and C₂H₆ as described § 1065.660(c)(2). Determine CH₄ as described in § 1065.660(d)(2) and C₂H₆ as described § 1065.660(e).

(e) Interference verification. Perform interference verification for FTIR analyzers using the procedures of § 1065.366. Certain interference gases can interfere with FTIR analyzers by causing a response similar to the hydrocarbon species of interest. When running the interference verification for these analyzers, use interference gases as follows: