The basic rule
| Filter type | Typical change interval |
|---|---|
| 1-inch fiberglass | Every 30 days |
| 1-inch pleated | Every 1–3 months |
| 4–5 inch media | Every 6–12 months |
| Washable | Clean monthly |
Change it sooner if...
- You have pets, especially ones that shed
- Someone in the home has allergies or asthma
- There's construction, renovation or wildfire smoke
- The system runs constantly in peak summer or winter
Choosing a MERV rating
MERV 8 is a good balance for most homes. MERV 11–13 captures finer particles but restricts airflow more, so check with a technician if your system is older or your ducts are small.
How to change it
- Turn the system off.
- Note the size printed on the old filter's frame.
- Install the new filter with the airflow arrow pointing toward the furnace or air handler.
- Write the date on the frame.
