Statutes, codes, and regulations
Code of Federal Regulations
Title 40 - PROTECTION OF ENVIRONMENTChapter I - ENVIRONMENTAL PROTECTION AGENCYSubchapter U - AIR POLLUTION CONTROLSPart 1065 - ENGINE-TESTING PROCEDURES
Subpart G - CALCULATIONS AND DATA REQUIREMENTS
Section 1065.670 - NO[X] intake-air humidity and temperature corrections

40 C.F.R. § 1065.670

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Current through October 31, 2024
Section 1065.670 - NO[X] intake-air humidity and temperature corrections

See the standard-setting part to determine if you may correct NOX emissions for the effects of intake-air humidity or temperature. Use the NOX intake-air humidity and temperature corrections specified in the standard-setting part instead of the NOX intake-air humidity correction specified in this part 1065. If the standard-setting part does not prohibit correcting NOX emissions for intake-air humidity according to this part 1065, correct NOX concentrations for intake-air humidity as described in this section. See § 1065.650(c)(1) for the proper sequence for applying the NOX intake-air humidity and temperature corrections. You may use a time-weighted mean intake air humidity to calculate this correction if your intake air humidity remains within a tolerance of ±0.0025 mol/mol of the mean value over the test interval. For intake-air humidity correction, use one of the following approaches:

(a) For compression-ignition engines operating on carbon-containing fuels and lean-burn combustion engines operating on fuels other than carbon-containing fuels, correct for intake-air humidity using the following equation:

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Example:

xNOxuncor = 700.5 [MICRO]mol/mol

xH2O = 0.022 mol/mol

xNOxcor = 700.5 · (9.953 · 0.022 + 0.832)

xNOxcor = 736.2 [MICRO]mol/mol

(b) For spark-ignition engines operating on carbon-containing fuels and stoichiometric combustion engines operating on fuels other than carbon-containing fuels, correct for intake-air humidity using the following equation:

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Example:

xNOxuncor = 154.7 [MICRO]mol/mol

xH2O = 0.022 mol/mol

xNOxcor = 154.7 · (18.840 · 0.022 + 0.68094)

xNOxcor = 169.5 [MICRO]mol/mol

(c) Develop your own correction, based on good engineering judgment.

40 C.F.R. §1065.670

75 FR 23056 , Apr. 30, 2010, as amended at 76 FR 57466 , Sept. 15, 2011; 88 FR 4686 , Jan. 24, 2023; 89 FR 29822 , Apr. 22, 2024
40 FR 43101, 7/1/2016; 84 FR 9243 , 4/15/2019; 88 FR 4686 , 3/27/2023; 89 FR 29822 , 6/21/2024