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.CH4 methane.cm--Centimetre(s).CO--Carbon monoxide.CO2--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. H2O--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).N2--Nitrogen.N2O nitrous oxide.NOX--Oxides of nitrogen.No.--Number.O2--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]