# 86.403-78 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<sub>4</sub> methane.
cm—Centimetre(s).
CO—Carbon monoxide.
CO<sub>2</sub>—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<sub>2</sub>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<sub>2</sub>—Nitrogen.
N<sub>2</sub>O nitrous oxide.
NO<sub>X</sub>—Oxides of nitrogen.
No.—Number.
O<sub>2</sub>—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]