Properties of Air
Air is the mixture of gases that make up Earth’s atmosphere. It primarily consists of approximately 78% nitrogen, 21% oxygen, and trace amounts of other gases like carbon dioxide, argon, and water vapor.
The following table provides a comprehensive list of air properties in both SI and US customary/Imperial units at normal temperature and pressure (NTP).
Click on the icon to switch between Metric and Imperial units.
| Physical Properties | Metric |
|---|---|
| Molar Mass | 28.964 g/mol |
| Density vs temperature | 1.204 kg/m3 |
| Dynamic Viscosity (25°C) vs temperature | 18.5 µPa·s |
| Speed of Sound in Gas (25°C) vs temperature | 346 m/s |
| Thermal Properties | Metric |
| Melting Point | -213.4 °C |
| Boiling Point | -194.3 °C |
| Thermal Conductivity (25°C) vs temperature | 0.0264 W/m·K |
| Specific Heat Capacity (Cp) | 1006 J/kg·K |
| Coefficient of Thermal Expansion | 3.43×10-3 1/°C |
| Critical Constants | Metric |
| Critical Pressure (Pc) | 3.774 mPa |
| Critical Temperature (Tc) | -140.7 °C |
| Critical Density (ρc) | 328 kg/m3 |
| Electrical Properties | Metric |
| Relative Permittivity (εr) | 1.00059 |
| Optical Properties | Metric |
| Refractive Index (589 nm) | 1.000293 |
Unless stated otherwise, all values are taken at room temperature (approximately 20°C or 68°F) and 1 atm pressure. (1 atm = 101,325 Pa)
Related Pages
References: 1) Cardarelli, François. Materials Handbook: A Concise Desktop Reference. Switzerland: Springer International Publishing, 2018. 2) CRC Handbook of Chemistry and Physics, 97th Edition. United Kingdom: CRC Press, 2016-2017. 3) Yaws, Carl L. The Yaws Handbook of Physical Properties for Hydrocarbons and Chemicals. Netherlands: Elsevier Science, 2015. 4) Fire Protection Guide to Hazardous Materials, 14th Edition. United States: National Fire Protection Association, 2010.