Quick Answer: Most homeowners should replace a 1-inch HVAC air filter ever 30-60 days. Homes with pets, allergies, or heavy HVAC use should replace filters every 30 days, while 4-inch media filters typically last 6-12 months. These are general guidelines. The ideal replacement schedule depends on your air filter type, pets, allergies, indoor air quality, and how often your HVAC system runs. If you're wondering how often to change your air filter, the answer depends on your