Find the right filter for your home.

A useful replacement has to fit the rack and work with the system’s airflow. Start with the equipment or filter-cabinet specification, compare the actual dimensions, and then choose a supported filtration rating. A higher number on the package does not fix a poor fit.

A ducted system may have a filter at a return grille, in a rack near the air handler, or inside a dedicated media cabinet. Locate the intended service access in the manual. Multiple systems or returns can use different sizes.

Do not assume that adding a second filter in series improves the installation. Use the filtration arrangement specified for the system. Mini-split indoor heads, portable air cleaners, car cabin filters, and refrigerator filters are different replacement tasks.

If you use a ducted heat pump, this sizing and MERV guidance applies to its specified central filter. For equipment maintenance beyond that filter, see the heat-pump maintenance guide.

MERV compares particle capture, but it is not a fit code or a direct measure of pressure drop. Two filters with the same rating can differ in area, media, and airflow resistance. Match the cabinet first and check manufacturer performance information for a proposed upgrade.

EPA recommends MERV 13, or the highest efficiency the system can accommodate. If compatibility is unclear, have an HVAC technician check the filtration arrangement and airflow. The MERV comparison explains what the rating does and does not establish.

Switch the system off as directed before opening the filter access. Observe the airflow arrow and the equipment’s indicated airflow direction. Install without crushing the frame, and close the access securely. A filter that rattles or leaves a gap needs a fit check.

Inspect the filter monthly. EPA notes that manufacturers commonly recommend replacement every 60–90 days, but deep-media and other filters can have different schedules. Follow the exact filter and equipment instructions, and replace sooner if the filter becomes heavily soiled. Heavy dust, renovation work, pets, and longer runtime can change how quickly a filter loads. A subscription reminder is convenient, but it does not inspect the filter for you.

Date the replacement and record the part used. Disposable filters should not be washed and put back unless the manufacturer explicitly designs them for that use. A wet filter is not a routine replacement interval issue; investigate the moisture source.

The references below support the technical checks in this guide. Use the instructions for your exact product or local conditions when they differ from a general example.