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Pleated furnace filter sliding into the furnace slot, with the airflow arrow on the frame pointing toward the furnace

Furnace and AC air filters

Which way does the furnace filter arrow point?

  • Updated Oct 23, 2026
  • 4 sources

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Quick answer

The arrow on the filter frame points toward the furnace (the blower motor), in the direction the air moves. Air comes from the return duct, goes through the filter, then into the blower. Filtrete and ENERGY STAR both say the arrow should point toward the blower or furnace.

Furnace filters by rating (check your actual size first):

Filtrete MPR 1000 (MERV 11) Filtrete MPR 1900 (MERV 13) Nordic Pure 16x25x1 filters

Airflow direction

Which way the arrow points Return duct Air comes back from the rooms › Filter Arrow points this way → toward the blower › Furnace blower Air goes in here, then is heated or cooled
Filtrete and ENERGY STAR: the arrow points toward the furnace blower, the way the air moves.

In a filter slot next to the furnace, the arrow points at the furnace cabinet. In a ceiling or wall return grille, the air is moving into the duct, so the arrow points into the duct, away from the room. Filtrete gives the same rule for 1-inch, 4 to 6-inch and refillable filters: arrow toward the blower motor.

How to change it (ENERGY STAR's steps)

  1. Find the filter. It's in a slot on the furnace or air handler, or behind a return grille.
  2. Turn the system off. Shut off the furnace, A/C and fan at the thermostat, the breaker or a switch.
  3. Note the arrow on the old filter before you pull it out, then remove it.
  4. Unwrap the new filter. Filtrete says to remove the plastic packaging and paper insert, leaving the cardboard frame intact.
  5. Slide it in with the arrow toward the furnace. ENERGY STAR says it should be a tight fit, so you may need to wiggle it.
  6. Close the cover and turn the system back on.

If it doesn't fit right

  • Too tight or won't close: check the size printed on the old frame. Sizes are rounded, so brands can differ a little. See nominal vs actual size.
  • Edge showing: ENERGY STAR says if there's no cover and you can see the filter's edge, seal the space with duct tape or a magnetic cover.

Turn the system off before you pull the filter. ENERGY STAR's steps have you switch off the furnace, A/C and fan before you open the cover.

How we work: the direction rule comes from Filtrete's install guide and ENERGY STAR. Steps follow ENERGY STAR's guide. Sources are listed below.

Questions people ask

Which way does the arrow on a furnace filter point?

Toward the furnace or blower motor, in the direction the air flows. Filtrete and ENERGY STAR both say this.

Which way does the arrow go in a ceiling return vent?

The air moves from the room into the duct, so the arrow points into the duct, toward the blower.

Do I take the plastic off a new filter?

Yes. Filtrete says to remove the plastic packaging and paper insert but leave the cardboard frame intact.

Sources

Last checked Oct 23, 2026. Turn the furnace, A/C and fan off before you change the filter, as ENERGY STAR says. Check your furnace manual for the filter types and ratings it can take.

  1. Filtrete: How to install an air filter
  2. ENERGY STAR: How to keep your HVAC system working efficiently
  3. Filtrete: Frequently asked questions
  4. Nordic Pure: How to measure an air filter

Keep going

Related guides

Furnace and AC air filtersRead the size on the old frame, know why a 16x25x1 filter may measure about 15.5 x 24.5 x 0.75, and measure the slot if the label is gone.Read guide
GuideHow often to change itEvery 3 months for 1-inch, every 12 months for 4-inch, and the conditions that mean sooner.Read guide
GuideMERV 8 vs 11 vs 13The EPA capture table for each rating, Filtrete MPR to MERV, and when MERV 13 makes sense.Read guide