Final answer:
An alcohol evaporator in air brake systems helps reduce the risk of ice forming in the air brake valves during cold weather by lowering the freezing point of moisture in the system.
Step-by-step explanation:
Some air brake systems have an alcohol evaporator which helps reduce the risk of ice in the air brake valves during cold weather. When it gets cold, water vapor present in the air can condense and freeze inside the brake valves, causing them to malfunction. The alcohol evaporator is designed to introduce alcohol vapor into the air brake system, which lowers the freezing point of the moisture, preventing ice formation. This allows the air brakes to function properly even in cold weather.