What is the purpose of the over-pressure safety valve?

• A. To prevent cabin pressure from exceeding the design limits of the aircraft structure
• B. To regulate the rate of cabin pressurization
• C. To vent cabin air to the outside
• D. To monitor differential pressure

Answer: (A)

The over-pressure safety valve serves as a relief device in the cabin pressurization system. Its job is to open at a preset differential pressure and vent cabin air to the outside, preventing the pressure from exceeding what the aircraft structure is designed to safely withstand. This acts as a safety backup to the normal controls that regulate cabin pressure; those controls manage rate and target pressure, while the safety valve only intervenes when the limit is reached. So, while it may vent to the outside when it activates, its primary purpose is to protect the structure from over-pressurization, not to continuously regulate pressurization.