Question What do air brakes use to make the brakes work? Answers Compressed air Outside air Non-compressed air Explanation Many large CMVs are equipped with air brakes. An air braking system uses compressed air to operate. Take a FREE Practice Test Now This questions appears in the following tests: Arizona Knowledge Test Class A , Maine Knowledge Test Class B , Wisconsin Knowledge Test Class B , Louisiana Passenger , Iowa Air Brakes , Michigan Air Brakes , New Mexico Air Brakes , Ohio Air Brakes ,