Air Composition

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

Air is a mixture of gases - 78% nitrogen and 21% oxygen - with traces of water vapor, carbon dioxide, argon, and various other components.

air composition

Air is usually modeled as a uniform (no variation or fluctuation) gas with properties averaged from the individual components.

GasRatio compared to Dry Air (%)Molecular Mass
- M -
(kg/kmol)
Chemical SymbolBoiling Point
By volumeBy 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 temperature
  • The composition of air is unchanged until elevation of approximately 10.000 m
  • The average air temperature diminishes at the rate of 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)

Other components in air

  • Sulfur dioxide - SO2 - 1.0 parts/million (ppm)
  • Methane - CH4 - 2.0 parts/million (ppm)
  • Nitrous oxide - N2O - 0.5 parts/million (ppm)
  • Ozone - O3 - 0 to 0.07 parts/million (ppm)
  • Nitrogen dioxide - NO2 - 0.02 parts/million (ppm)
  • Iodine - I2 - 0.01 parts/million (ppm)
  • Carbon monoxide - CO - 0 to trace (ppm)
  • Ammonia - NH3 - 0 to trace (ppm)

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

  • 76 Centimeters (760 mm) of Mercury
  • 29.921 Inches of Mercury
  • 10.332 Meters of Water
  • 406.78 Inches of Water
  • 33.899 Feet of Water
  • 14.696 Pound-Force per Square Inch
  • 2116.2 Pounds-Force per Square Foot
  • 1.033 Kilograms-Force per Square Centimeter
  • 101.33 Kilopascal

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

Related Topics

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

Related Documents

  • Specific Heat Ratio of Air - Specific Heat Ratio of air at temperatures from -40 - 1000 oC (-40 - 1500 oF) at standard atmospheric pressure - 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 used for air with water vapor - or moist air
  • Air Properties - Temperature, density, specific heat, thermal conductivity, expansion coefficient, kinematic viscosity and Prandtl's number for temperatures ranging -150 - 400 oC
  • Density of Dry Air, Water Vapor and Moist Humid Air - Calculate the density of dry air, water vapor or the mixture of air and water vapor - moist or humid air
  • Air Solubility in Water - Amount of air that can be dissolved in water - decrease with temperature - increase with pressure
  • Nitrogen - Specific Heat - Specific heat of Nitrogen Gas - N2 - at temperatures ranging 175 - 6000 K
  • 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
  • Oxygen - Specific Heat - Specific heat of Oxygen Gas - O2 - at temperatures ranging 175 - 6000 K
  • Ideal Gas Properties Oxygen - Enthalpy, Internal Energy and Entropy of Oxygen
  • 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

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