Abbreviations.

The abbreviations used in this subpart have the following meanings in both capital and lowercase: ASTM—American Society for Testing and Materials. C—Celsius. cc—Cubic centimetre(s). cfh—Cubic feet per hour. cfm—Cubic feet per minute. CH 4 methane. cm—Centimetre(s). CO—Carbon monoxide. CO 2 —Carbon dioxide. Conc—Concentration. cu.—Cubic. CVS—Constant volume sampler. EGR—Exhaust gas recirculation. EP—End point. EPA—Environmental Protection Agency. F—Fahrenheit. h—hour. HC—Hydrocarbon(s). Hg—Mercury. H 2 O—Water. in.—Inch(es). K—Kelvin. kg—Kilogram(s). km—Kilometre(s). kpa—Kilopascals. lb—Pound(s). m—Metre(s). mph—Miles per hour. mm—Millimetre(s). N 2 —Nitrogen. N 2 O nitrous oxide. NO X —Oxides of nitrogen. No.—Number. O 2 —Oxygen. Pa—Pascal(s). Pb—lead. ppm—Parts per million by volume. psi—Pounds per square inch. psig—Pounds per square inch gauge. R—Rankine. rpm—Revolutions per minute. wt—Weight. °—Degree(s). %—Percent. [42 FR 1126, Jan. 5, 1977, as amended at 74 FR 56373, Oct. 30, 2009]