What is the minimum acceptable pressure build in an air brake system after 3 minutes?

Answer: D — 90 psi

In an air brake system, the minimum acceptable pressure that should be maintained after three minutes is crucial for ensuring the system is functioning correctly and safely. Maintaining a pressure of 90 psi indicates that the air brake system is in a suitable condition to provide effective braking performance. Pressure levels below this threshold may indicate a potential issue with the air compressor or leaks within the system, which could compromise the braking ability of the vehicle. Therefore, achieving and maintaining 90 psi is essential for the safety of the vehicle and its occupants, ensuring that the air brake system can activate properly when needed. This standard reflects the operational requirements necessary to ensure the reliability and safety of air brakes in commercial vehicles, as well as compliance with safety regulations.