Furnace filters and return air filters play crucial roles in maintaining indoor air quality. Furnace filters remove particulate matter from forced air before it reaches heating and cooling components, while return air filters catch airborne pollutants as air returns to the HVAC system. The Minimum Efficiency Reporting Value (MERV) rating indicates filter efficiency in removing harmful particles. Regular HVAC maintenance, including filter changes, is essential for better health, reduced energy consumption, and humidity control.