What role do thermostats play in HVAC systems?

Thermostats are essential components of HVAC systems as they serve the primary function of regulating temperature within a space. By sensing the current temperature, thermostats determine whether the environment is at the desired setting (the "setpoint"). When the temperature deviates from this setpoint, the thermostat activates or deactivates the heating or cooling output accordingly. This function helps maintain a comfortable indoor climate and ensures energy efficiency, as the HVAC system only operates as needed.

Other options either misrepresent the function of thermostats or pertain to different components of the HVAC system. Air filtration is handled by filters, humidity levels are typically controlled by humidifiers or dehumidifiers, and gas monitoring for safety involves sensors not found in standard thermostats. Thus, while the other options may involve elements related to HVAC systems, they do not accurately describe the role of thermostats.