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MODEL RELEASED. Breathalyser. Driver's view of a policeman reaching into a car with a breathalyser in his outstretched hand. Electronic breathalysers use alcohol to produce an electric current. Breath from the tube is drawn into a battery-like cell, where it touches a platinum electrode. The platinum causes any alcohol present to oxidise into acetic acid, releasing electrons as it does so. These electrons flow to another electrode, producing a current. The strength of the current is used to estimate out how much alcohol the subject has drunk. (KEYSTONE/SCIENCE PHOTO LIBRARY/ADAM HART-DAVIS)