Check the air filter on your HVAC unit every month, especially during heavy use months (winter and summer). If the filter looks dirty after a month, change it. At a minimum, change the filter every 3 months. A dirty filter will slow down air flow and make the system work harder to keep you warm or cool — wasting energy. Even worse, a dirty air filter will eventually start releasing some of the dirt it originally trapped back into the air stream. Keeping your air filter clean will prevent dust and dirt from building up in the system — leading to expensive maintenance and/or early system failure. Contact your American Standard Service Representative today with any questions.