Change your air filter on regular schedule to keep the air for you and the a/c unit cleaner.Check your filter 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,leading to expensive maintenance and/or early system failure. A clean filter will help to prevent dust and dirt from building up in the system thus providing cleaner air in the home.