What is the purpose of a thermostat in an HVAC system?

The purpose of a thermostat in an HVAC system is to measure and control temperature. A thermostat serves as a key component in maintaining the desired indoor climate by detecting the current temperature of the environment and comparing it to the set temperature on the unit. When the temperature deviates from this set point, the thermostat sends signals to the HVAC system to either activate heating or cooling modes, allowing for efficient and comfortable temperature regulation within a space. This functionality is crucial for energy efficiency and ensuring occupant comfort.

In contrast to this, circulating air pertains to the role of fans or blowers in the HVAC system rather than the thermostat itself. Filtering pollutants is a function of air filters, which are designed to clean the air circulating within the system. Igniting the burner is a specific task related to certain heating systems, particularly gas-fired units, and is not the primary function of the thermostat. Thus, the correct answer focuses on the thermostat's essential role in temperature measurement and control.