Question Alcohol evaporators are: Answers Illegal. Used to add alcohol to braking systems to prevent items from freezing. Only allowed on vehicles carrying hazardous materials. Explanation Some air brake systems include an alcohol evaporator. The evaporator introduces alcohol into the braking system to prevent the formation of ice, which can cause damage. Take a FREE Practice Test Now This questions appears in the following tests: Arkansas Knowledge Test Class A , Kentucky Air Brakes , South Dakota Air Brakes ,