» Gas and air redirects here, for the 1923 film, see Gas and Air (film)Entonox, referred to colloquially as gas and air, is an analgesic used to ease pain during labour, trauma and minor surgical procedures. Entonox is the trade name for a mixture of fifty percent nitrous oxide (N2O or laughing gas) and fifty percent oxygen (O2). Entonox is administered by inhalation from a cylinder at a pressure of 137 bar (in the UK) or from a pipeline supply. Its analgesic effect is strong (equivalent to 5 t… (More on Entonox)