What is the purpose of a fire extinguisher's pressure gauge?

The purpose of a fire extinguisher's pressure gauge is to ensure that the extinguisher is pressurized and ready for use. The pressure gauge provides a visual indication of the internal pressure of the extinguisher. A needle in the green zone of the gauge signifies that the extinguisher is properly pressurized. If the needle is in the red zone, it suggests that the extinguisher may not operate effectively in the event of a fire, either due to being over-pressured or under-pressured. Therefore, the gauge is crucial for assessing the readiness and safety of the extinguisher prior to use, allowing users to quickly verify its condition before responding to an emergency.