Air

Air

1. The mixture of gases comprising the earth's atmosphere.
The percent by volume of those gases found in relatively constant amount in dry air near sea level in very nearly as follows:

ELEMENT</P>	%</P>
nitrogen (N2)	78.084
oxygen (O2)	20.9476
argon (A)	0.934
carbon dioxide (CO2)	0.0314 (variable)
neon (Ne)	0.001818
helium (He)	0.000524
methane (CH4)	0.0002 (variable)
krypton (Kr)	0.000114
hydrogen (H2)	0.00005
nitruous oxide (N2O)	0.00005
xenon (Xe)	0.0000087

_{This table is from the 1965 edition of the Aerospace Dictionary.}

In addition to the above constituents there are many variable constituents. Chief of these is water vapor, which may vary from zero to volume percentages close to 4 percent. Ozone, sulfur dioxide, ammonia, carbon monoxide, iodine, and other trace gases occur in small and varying amounts.
The above composition of dry air is true to about 90 kilometers. See upper atmosphere.

2. The realm or medium in which aircraft operate.

This definition page has been automatically generated. You can help ExoDictionary by expanding, updating, or correcting it.

This autostub has not yet had its initial copyediting proof and may contain significant formatting and even factual errors. You can improve Exodictionary by cleaning up the page markup and verifying that the definition is correct and then removing this tag.

This autostub has not yet had its initial categorization proof and may be categorized incorrectly. You can improve Exodictionary by removing inappropriate categories and then removing this tag.

References

This article is based on NASA's Dictionary of Technical Terms for Aerospace Use