Nitrous oxide. Computer model of a molecule of nitrous oxide. Atoms are represented as spheres and are colour-coded: nitrogen (blue) and oxygen (red). Nitrous oxide is a colourless non-flammable gas at room temperature. When inhaled it induces feelings of euphoria and acts as an analgesic (painkiller). Due to this, nitrous oxide is mixed with oxygen and used as an anaesthetic in dentistry and surgery. It is also used as an aerosol propellant, particularly in the food industry. Nitrous oxide is a greenhouse gas and the third largest contributor to global warming after carbon dioxide and methane.