Short answer
Change a 1-inch furnace filter every one to three months and a 4- or 5-inch media filter every six to twelve months. Change more often with pets, allergies, construction dust or heavy summer and winter use.
Why it matters
A clogged filter restricts airflow, which can freeze the AC coil in summer and trip the furnace's high-limit switch in winter. It also raises energy use.
Choosing a MERV rating
- MERV 8: good basic protection for equipment.
- MERV 11–13: better for allergies; best in a 4-inch media cabinet.
- Very restrictive 1-inch filters can choke airflow.
Kansas City pollen seasons
Tree pollen in spring, grass in early summer and ragweed into fall make filter changes at the start of each season a good habit.
When to call a technician
- You want to upgrade to a media filter cabinet.
- The filter gets dirty within weeks.
What the technician does: see air filtration & purification.
Common questions
Which way does the arrow go?
The airflow arrow points toward the furnace, away from the return.
Editorial note: this guide is general information for Kansas City-area homeowners, not a diagnosis. Conditions vary by home, so a licensed HVAC technician should confirm the cause before any repair.