How many safety valves are used to ensure the cabin pressure differential does not exceed limits?

The correct answer is two because the CRJ550 is designed with a dual safety valve system to ensure that the cabin pressure differential does not exceed safe operational limits. This dual configuration serves as a redundancy measure—should one valve fail, the other can still function to maintain safety and pressure regulation. This is crucial in preventing pressure overload situations that could lead to structural damage to the cabin or other safety concerns. Using two safety valves provides a balance between reliability and safety, ensuring that the aircraft can maintain proper cabin pressure in various operating conditions.