The air dryer in trucks is a device that removes water vapor, oil and other contaminants from the compressed air system. All trucks that have air brakes must have an air compressor driven by the engine. The air compressor keeps the air brake system charged up and ready to stop the truck and trailer.

Air dryers are located between the compressor and reservoirs and work hard to remove solids, liquids and vapors that can damage the entire air brake system.