The following symbols, acronyms, and abbreviations apply to this part: [deg]--degrees.ASTM--American Society for Testing and Materials.ATV--all-terrain vehicle.cc--cubic centimeters.CFR--Code of Federal Regulations.CH4 methane.cm--centimeter.C--Celsius.CO--carbon monoxide.CO2--carbon dioxide.EPA--Environmental Protection Agency.F--Fahrenheit.g--grams.g/gal/day--grams per gallon per test day.g/m\2\/day--grams per meter-square per test day.HC--hydrocarbon.Hg--mercury.hr--hours.km--kilometer.kW--kilowatt.LPG--liquefied petroleum gas.m--meters.mm--millimeters.mW--milliwatts.N2O nitrous oxide.NARA--National Archives and Records Administration.NMHC--nonmethane hydrocarbons.NOX--oxides of nitrogen (NO and NOX).psig--pounds per square inches of gauge pressure.rpm--revolutions per minute.SAE--Society of Automotive Engineers.SI--spark-ignition.THC--total hydrocarbon.THCE--total hydrocarbon equivalent.U.S.C.--United States Code. [67 FR 68347, Nov. 8, 2002, as amended at 70 FR 40510, July 13, 2005; 74 FR 56511, Oct. 30, 2009]