| Table 1: Average composition of the atmosphere up to an altitude of 25 km. | ||
|---|---|---|
| Gas Name | Chemical Formula | Percent Volume |
| Nitrogen | N2 | 78.08% |
| Oxygen | O2 | 20.95% |
| Argon | Ar | 0.93% |
| * Water | H2O | 0.25% (0-4% range) |
| * Carbon dioxide | CO2 | 0.0415% |
| Neon | Ne | 0.0018% |
| Helium | He | 0.0005% |
| * Methane | CH4 | 0.00017% |
| Hydrogen | H2 | 0.00005% |
| * Nitrous oxide | N2O | 0.00003% |
| * Ozone | O3 | 0.000004% |
| * variable gases | ||