What is the maximum allowable air pressure loss after the initial drop when checking air brake leaks?

When checking air brake leaks, the maximum allowable air pressure loss after the initial drop is 3 psi. This standard is set to ensure that the air brake system maintains sufficient pressure for safe operation. A leak that allows for a loss greater than 3 psi over a specified time indicates that there may be a significant issue within the brake system, which could compromise the safety of the bus. Regularly monitoring this pressure loss helps in identifying any leaks early and addressing them promptly, ensuring the brakes function effectively when needed. Maintaining the air pressure within this limit is critical for the reliability and responsiveness of the braking system, which is essential in a school bus where the safety of children is a priority.