How to replace an air filter

Cleaner air and a happier furnace, in five minutes.

Time: 5 min · Difficulty: Easy · 5 steps

What you need

Steps

  1. Turn the system off

    A finger sliding a thermostat switch to off

    Switch the heating or air conditioning off at the thermostat so it isn’t pulling air while the filter is out.

    Tip: off first, always

  2. Slide the old filter out

    A dusty grey filter sliding out of a wall vent

    Find the filter behind the big return vent or in a slot beside the furnace. Open the grille and slide the old filter out.

    Tip: grey & fuzzy = overdue

  3. Read the size and the arrow

    A magnifying glass over the size and airflow arrow on a filter frame

    The size is printed on the frame, like 16×25×1. Notice which way the airflow arrow points before you throw the old one out.

    Tip: snap a photo of the label

  4. Slide in the new one

    A clean white filter sliding into the vent

    Push the new filter in with the airflow arrow pointing toward the furnace, away from the room.

    Tip: arrow points to the furnace

  5. Date it, switch back on

    A marker writing the date on the edge of a new filter

    Write today’s date on the frame, close the grille, and turn the system back on. Check it again in 1 to 3 months.

    Tip: every 1–3 months

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