### U.S. Code of Federal Regulations

Regulations most recently checked for updates: Sep 11, 2024

(a) *Scope and frequency.* If you use a FID analyzer and an NMC to measure methane (CH

(b) *Measurement principles.* An NMC is a heated catalyst that removes nonmethane hydrocarbons from an exhaust sample stream before the FID analyzer measures the remaining hydrocarbon concentration. An ideal NMC would have a CH*PF**PF*

(c) *System requirements.* We do not require that you limit NMC penetration fractions to a certain range. However, we recommend that you optimize an NMC by adjusting its temperature to achieve a *PF**PF**PF*

(d) *Procedure for a FID calibrated with the NMC.* The following procedure describes the recommended method for verifying NMC performance and the required method for any gaseous-fueled engine, including dual-fuel and flexible-fuel engines.

(1) Select CH

(2) Start, operate, and optimize the NMC according to the manufacturer's instructions, including any temperature optimization.

(3) Confirm that the FID analyzer meets all the specifications of § 1065.360.

(4) Start and operate the FID analyzer according to the manufacturer's instructions.

(5) Zero and span the FID with the NMC as you would during emission testing. Span the FID through the NMC by using CH

(6) Introduce the C

(7) Allow time for the analyzer response to stabilize. Stabilization time may include time to purge the NMC and to account for the analyzer's response.

(8) While the analyzer measures a stable concentration, record 30 seconds of sampled data. Calculate the arithmetic mean of the analytical gas mixture.

(9) Calculate a reference concentration of C*RFPF**RFPF**RFPF**RFPF**RFPF*

(10) For any gaseous-fueled engine, including dual-fuel and flexible-fuel engines, repeat the steps in paragraphs (d)(6) through (9) of this section, but with the CH*RFPF**RFPF*

(11) Use *RFPF**RFPF*

(e) *Procedure for a FID calibrated with propane, bypassing the NMC.* If you use a single FID for THC and CH*PF**PF*

(1) Select CH

(2) Start and operate the NMC according to the manufacturer's instructions, including any temperature optimization.

(3) Confirm that the FID analyzer meets all the specifications of § 1065.360.

(4) Start and operate the FID analyzer according to the manufacturer's instructions.

(5) Zero and span the FID as you would during emission testing. Span the FID by bypassing the NMC and by using C

(6) Introduce the C

(7) Allow time for the analyzer response to stabilize. Stabilization time may include time to purge the NMC and to account for the analyzer's response.

(8) While the analyzer measures a stable concentration, record 30 seconds of sampled data. Calculate the arithmetic mean of the analytical gas mixture.

(9) Reroute the flow path to bypass the NMC, introduce the C

(10) Divide the mean C*PF*

(11) Repeat the steps in paragraphs (e)(6) through (10) of this section, but with the CH*PF*

(f) *Procedure for a FID calibrated with CH**bypassing the NMC*. If you use a FID with an NMC that is calibrated with CH*RFPF**PF*

(1) Select CH

(2) Start and operate the NMC according to the manufacturer's instructions, including any temperature optimization.

(3) Confirm that the FID analyzer meets all the specifications of § 1065.360.

(4) Start and operate the FID analyzer according to the manufacturer's instructions.

(5) Zero and span the FID as you would during emission testing. Span the FID by bypassing the NMC and by using CH

(6) Introduce the C

(7) Allow time for the analyzer response to stabilize. Stabilization time may include time to purge the NMC and to account for the analyzer's response.

(8) While the analyzer measures a stable concentration, record 30 seconds of sampled data. Calculate the arithmetic mean of the analytical gas mixture.

(9) Divide the mean C*RFPF*

(10) Introduce the CH

(11) Allow time for the analyzer response to stabilize. Stabilization time may include time to purge the NMC and to account for the analyzer's response.

(12) While the analyzer measures a stable concentration, record 30 seconds of sampled data. Calculate the arithmetic mean of these data points.

(13) Reroute the flow path to bypass the NMC, introduce the CH

(14) Divide the mean CH*PF*

(g) *Test gas humidification.* If you are generating gas mixtures as a function of the molar water concentration in the raw or diluted exhaust according to paragraph (d) of this section, create a humidified test gas by bubbling the analytical gas mixture that meets the specifications in § 1065.750 through distilled H*U*

(1) If the sample does not pass through a dryer during emission testing, generate at least five different H

(2) If the sample passes through a dryer during emission testing, humidify your test gas to an H