Air Composition

Dry air is a mechanical mixture of nitrogen, oxygen, carbon dioxide and more

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Air is a mixture of gases, 78% nitrogen and 21% oxygen with traces of water vapor, carbon dioxide, argon, and various other components. We usually model air as a uniform (no variation or fluctuation) gas with properties that are averaged from all the individual components.

Gas Ratio compared to Dry Air (%) Molecular Mass
- M -
 (kg/kmol)		 Chemical Symbol Boiling Point
By volume By weight K (oC)
Oxygen 20.95 23.20 32.00 O2 90.2 -182.95
Nitrogen 78.09 75.47 28.02 N2 77.4 -195.79
Carbon Dioxide 0.03 0.046 44.01 CO2 194.7 -78.5
Hydrogen 0.00005 ~ 0 2.02 H2 20.3 -252.87
Argon 0.933 1.28 39.94 Ar 84.2 -186
Neon 0.0018 0.0012 20.18 Ne 27.2 -246
Helium 0.0005 0.00007 4.00 He 4.2 -269
Krypton 0.0001 0.0003 83.8 Kr 119.8 -153.4
Xenon 9 10-6 0.00004 131.29 Xe 165.1 -108.1

The water or vapor content in air varies. The maximum moisture carrying capacity of air depends primarily on the temperature.

The composition of air is unchanged until the height of approximately 10.000 m.

The average air temperature diminishes at the rate of about 0.6oC for each 100 m vertical height

"One Standard Atmosphere" is defined as the pressure equivalent to that exerted by a 760 mm column of mercury at 0oC sea level and at standard gravity (32.174 ft/sec2).

Common Pressure Units frequently used as alternative to "one Atmosphere"

More about Temperature, Density, Specific heat, Thermal Conductivity - the properties of air.

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Related Topics

  • Air Psychrometrics Air psychrometrics are the study of moist and humid air and the change of air condition - psychrometric charts, Mollier diagrams, air temperature and absolute and relative humidity, moisture content ..
  • Material Properties Material properties - density, heat capacity, viscosity and more - for gases, fluids and solids

Related Documents

  • Air Properties Air properties - temperature, density, specific heat, thermal conductivity, expansion coefficient, kinematic viscosity and Prandtl number for temperatures between -150oC and 400oC.
  • Specific Heat Ratio of Air Specific Heat Ratio of air at temperatures from -40 to 1.000oC (-40 to 1.500oF) at standard atmospheric pressure - in Imperial and SI Units
  • Humid Air and the Ideal Gas Law The Ideal Gas Law relating pressure, temperature, and volume of an ideal or perfect gas can also be used for air with water vapor - moist air
  • Molecular Mass of Air Dry air is a mixture of gases where the molecular weight can be calculated by adding the weight of each component
  • Density of Dry Air, Water Vapor and Moist Humid Air Calculating the density of dry air, water vapor or the mixture of air and water vapor - moist or humid air
  • Dry Air Properties Dry air properties at temperatures ranging 175 - 1900 K - specific heat capacity, ratio of specific heats, dynamic viscosity, thermal conductivity, Prandtl number, density and kinematic viscosity
  • Nitrogen - Specific Heat Capacity Specific heat capacity of Nitrogen Gas - N2 - at temperatures ranging 175 - 6000 K
  • Oxygen - Specific Heat Capacity Specific heat capacity of Oxygen Gas - O2 - at temperatures ranging 175 - 6000 K
  • Ideal Gas Properties Oxygen Enthalpy, Internal Energy and Entropy of Oxygen

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