Question Air pressure should build up in a single air system within: Answers 15 minutes. 12 minutes. Three minutes. One minute. Explanation In a vehicle with a single air brake system, after the engine is at operating rpms, the pressure in the air system should generally build from 50 to 90 psi within three minutes. Take a FREE Practice Test Now This questions appears in the following tests: Wyoming Knowledge Test Class A , West Virginia Double , Connecticut Air Brakes , Nevada Air Brakes ,