{"data":{"id":"us/40-cfr-1065.670","jurisdiction":"us","citation":"40 CFR 1065.670","heading":"NOX intake-air humidity and temperature corrections.","body":"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:\n(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:\nExample:\nxNOxuncor = 700.5 µmol/mol\nxH2O = 0.022 mol/mol\nxNOxcor = 700.5 · (9.953 · 0.022 + 0.832)\nxNOxcor = 736.2 µmol/mol\n(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:\nExample:\nxNOxuncor = 154.7 µmol/mol\nxH2O = 0.022 mol/mol\nxNOxcor = 154.7 · (18.840 · 0.022 + 0.68094)\nxNOxcor = 169.5 µmol/mol\n(c) Develop your own correction, based on good engineering judgment.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER U—AIR POLLUTION CONTROLS","PART 1065—ENGINE-TESTING PROCEDURES","Subpart G—Calculations and Data Requirements"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"0b9465e960fd792d5c70a2da20b9ef6945eceef779b87e3a5b1bb1dafb55e249","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-1065.667","next":"us/40-cfr-1065.672"},"notice":"GroundRules: Original legal text. Not legal advice."}