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. This questions appears in the following tests: Arkansas Air Brakes Illinois Air Brakes Massachusetts Air Brakes Nevada Air Brakes South Dakota Air Brakes Utah Class A Knowledge Test West Virginia Class A Knowledge Test