A pressure governor operates by:

A pressure governor plays a critical role in the operation of fire pumps by regulating the engine speed based on the pump pressure. When the demand for water changes—such as when a nozzle is opened or closed—the pressure governor adjusts the engine speed to maintain the desired pump discharge pressure. This functionality allows for consistent performance and prevents fluctuations that could impact the firefighting operation.

By controlling the engine speed, the governor ensures that the fire apparatus can deliver the required flow and pressure while also optimizing fuel efficiency and reducing wear on the engine. This automatic adjustment is crucial in fire scenarios where rapid changes in water demand can occur, allowing firefighters to maintain effective water supply without the need for manual intervention.

Other options, such as controlling the water discharge rate or nozzle pressure, do not accurately describe the primary function of a pressure governor. These functions may be influenced by the performance of the governor, but they do not encapsulate its primary role. The option relating to limiting pump intake pressure is also not the focus of what a pressure governor does, as it specifically addresses the relationship between engine speed and output pressure from the pump, which is essential in fire ground operations.