Preferred Label : composition of pure air;
Detailed label : composition of pure air in atmospheric chemistry;
IUPAC definition : The composition of air is variable with respect to several of its components (e.g.
CH sub 4 /sub , CO sub 2 /sub , H sub 2 /sub O) so 'pure' air has no precise meaning;
it is commonly considered to be air which is free of dust, aerosols and reactive gaseous
contaminants of anthropogenic origin. The composition of the major components in dry
air is relatively constant (percent by volume given): nitrogen, 78.084; oxygen, 20.946;
argon, 0.934; carbon dioxide, 0.033; neon, 0.0018; helium, 0.000524; methane, 0.00016;
krypton, 0.000114; hydrogen 0.00005; nitrous oxide, 0.00003; xenon, 0.0000087. The
concentrations of carbon dioxide, methane, nitrous oxide, the chlorofluorocarbons
and some other species of anthropogenic origin are increasing measurably with time.
Relative clean air which is free of most reactive anthropogenic pollution (NO, NO
sub 2 /sub , SO sub 2 /sub , non-methane hydrocarbons, etc.), often used as a reference
sample in the calibration and operation of instruments, is purchased under the designation
of zero air.;
Origin ID : C01214;
See also
The composition of air is variable with respect to several of its components (e.g.
CH sub 4 /sub , CO sub 2 /sub , H sub 2 /sub O) so 'pure' air has no precise meaning;
it is commonly considered to be air which is free of dust, aerosols and reactive gaseous
contaminants of anthropogenic origin. The composition of the major components in dry
air is relatively constant (percent by volume given): nitrogen, 78.084; oxygen, 20.946;
argon, 0.934; carbon dioxide, 0.033; neon, 0.0018; helium, 0.000524; methane, 0.00016;
krypton, 0.000114; hydrogen 0.00005; nitrous oxide, 0.00003; xenon, 0.0000087. The
concentrations of carbon dioxide, methane, nitrous oxide, the chlorofluorocarbons
and some other species of anthropogenic origin are increasing measurably with time.
Relative clean air which is free of most reactive anthropogenic pollution (NO, NO
sub 2 /sub , SO sub 2 /sub , non-methane hydrocarbons, etc.), often used as a reference
sample in the calibration and operation of instruments, is purchased under the designation
of zero air.
