What does it indicate when the safety valves release air?

Answer: B — The pressure has exceeded 150 psi

When the safety valves release air, it indicates that the pressure in the air brake system has exceeded a safe limit, which is typically set around 150 psi. The purpose of the safety valve is to prevent excessive pressure that could potentially lead to a failure or rupture in the air system. By releasing air when the pressure surpasses this threshold, the safety valve helps maintain safe operating conditions and protects the integrity of the air brake system. This function is crucial because air brake systems rely on maintaining a specific pressure range to operate effectively. If the pressure were to continuously exceed safe limits without a means of release, it could result in serious safety hazards, such as component failure or brake malfunctions. Understanding the role of safety valves in air brake systems is essential for ensuring both vehicle safety and functionality.