From AMS Glossary
Colorless gas, formula N2O, released by bacterial activity at the earth's surface.
It has an atmospheric lifetime of about 160 years and is currently present at a level of about 330 ppb. Its atmospheric significance is that it is transported into the stratosphere, where its reaction with excited oxygen atoms (O1D) is the major source of active nitrogen; it is also a major greenhouse gas. In large amounts, it has anesthetic properties (laughing gas).