A pressurestat responds to _____.

A pressurestat is a type of control device that is specifically designed to monitor and respond to changes in system pressure. It operates by detecting the pressure within a system, such as HVAC or refrigeration systems, and activating or deactivating components based on preset pressure thresholds. This functionality is critical in ensuring that the system operates within safe and efficient pressure parameters, which can help prevent malfunctions or inefficiencies.

The other options relate to different types of sensors or controls. Temperature changes are typically monitored by thermostats, while humidity levels are managed by hygrometers or humidistats. Voltage fluctuations are generally monitored by devices intended for electrical management. Thus, a pressurestat's primary role is to respond to system pressure, making it essential for maintaining the operational integrity of pressure-dependent systems.