Which component is crucial for maintaining air quality in HVAC systems?

Filters are crucial for maintaining air quality in HVAC systems because they serve the essential function of removing dust, allergens, and other pollutants from the air circulating through the system. By trapping these particles, filters help to ensure that the air delivered into the living spaces is clean and healthy for occupants. This not only improves indoor air quality but also protects the HVAC system itself from damage caused by dirt accumulation on components like coils and fans.

While other components like expansion valves, compressors, and thermostats play important roles in the operation and efficiency of HVAC systems, they do not contribute directly to air quality. Expansion valves regulate refrigerant flow, compressors circulate refrigerant, and thermostats control temperature settings, but none of these functions involve filtering or purifying the air that moves through the system. Thus, the presence of high-quality filters is paramount for ensuring that the air distributed throughout a building remains free of harmful contaminants.