Carrier and Bryant High Efficiency filters should be changed on a regular basis. We recommend checking the air filter on 3 month intervals to establish the interval the air filter should be changed at. We also recommend using only Carrier or Bryant filters in a Carrier brand cabinet. When you use a high end filter such as the Carrier or Bryant air filter it does a better job of trapping dust and pollution. To be effective the air filter media must be more dense than a standard air filter. This means the air filter will be more restrictive to air flow. Consequently if you allow the aire filter to load up with dirt it can affect the operating efficiency of the equipment and can also lead to equipment damage. We recommend the Carrier and Bryant High Efficiency air filter be changed when it begins to appear dirty.