MODEL RELEASED. Roadside breathalyser. Driver breathing into the mouthpiece of a breathalyser. He is suspected of drink driving. An electronic breathalyser uses alcohol from a suspect's breath to produce an electric current. The strength of the current is used to estimate how much alcohol a driver has drunk. The legal blood alcohol consumption (BAC) limit in the UK is 80 milligrams of alcohol per 100 millimetres of blood or 35 micrograms of alchol per 100 millimetres of breath (Road Traffic Act, 1988). Photographed in the UK.