Air pressure should build up in a single air system within: Question Air pressure should build up in a single air system within: Answers 15 minutes. 12 minutes. Three minutes. Explanation In single air systems, air pressure should build from approximately 50 to 90 psi within three minutes. This questions appears in the following tests: California Air Brakes Hawaii Class B Knowledge Test Hawaii Class B Knowledge Test Idaho Air Brakes Maine Air Brakes Maryland Class B Knowledge Test Minnesota Class B Knowledge Test Nevada Air Brakes Nevada Air Brakes New Mexico Air Brakes Ohio Double Rhode Island Class B Knowledge Test Rhode Island Double Rhode Island Air Brakes Vermont Class B Knowledge Test Washington Class B Knowledge Test