Nitrous oxide

Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an oxide of nitrogen with the formula N
₂O. At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen.

Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain-reducing effects, and it is on the World Health Organization's List of Essential Medicines. Its colloquial name, "laughing gas", coined by Humphry Davy, describes the euphoric effects upon inhaling it, which cause it to be used as a recreational drug inducing a brief "high". When abused chronically, it may cause neurological damage through inactivation of vitamin B₁₂. It is also used as an oxidiser in rocket propellants and motor racing fuels, and as a frothing gas for whipped cream.

Nitrous oxide is also an atmospheric pollutant, with a concentration of 333 parts per billion (ppb) in 2020, increasing at 1 ppb annually. It is a major scavenger of stratospheric ozone, with an impact comparable to that of CFCs. About 40% of human-caused emissions are from agriculture, as nitrogen fertilisers are digested into nitrous oxide by soil micro-organisms. As the third most important greenhouse gas, nitrous oxide substantially contributes to global warming. Reduction of emissions is an important goal in the politics of climate change.