HVAC systems are used to provide a comfortable indoor environment by controlling the temperature, humidity, and air quality of a space. HVAC systems are designed to maintain a consistent temperature and humidity level, while also providing ventilation to remove pollutants and stale air from the space. HVAC systems are also used to reduce energy costs by using energy-efficient components and systems, such as programmable thermostats and variable speed fans. Additionally, HVAC systems can help reduce the spread of airborne illnesses by filtering and purifying the air.