Posted by: Valley Services HVAC | December 23, 2009

How do you change a forced-air furnace filter?

As we have been discussing air quality and the importance of changing filters, it is necessary to explain exactly how to change a forced-air furnace filter.  Knowing what is in the air should be enough to convince you to change yours regularly.  The air in your home is filled with dead skin, dust mite feces, dust, mold spores, and more particles that can be filtered out as long you change the filter.  It is fairly simple.

There are a variety of sizes, styles, and prices of furnace filters, but changing each of them is similar.

  1. Before you start, turn off your furnace fan.  Either switch off at your furnace, or on the thermostat, switch to off.
  2. Locate your filter. It should be located near the bottom of your furnace where the ductwork meets with the furnace.  This is where the air comes from your home, to be filtered and then sent back as warm or cold air through the top of your furnace.

It might be hidden behind a slot of sheet metal that can be moved.  If you cannot find it, consult your furnace manual or call a service technician.

3. Grasp the edge of the filter and pull out of slot.

4. Take the new filter, look at which way the arrow points, have it pointing toward furnace, the direction of air flow.  Putting in backwards decreases efficiency.

5. Close up slot, if needed. Change filter as recommended, for the 1 inch pleated filter, usually 2-3 months, depending on how much usage.

6.  It only filters the air if your blower is running.  If you have a variable speed blower, keep it running at a low speed all the time for the best air quality.

Other questions concerning your furnace? Click here.

Thanks again!

Bryan Corbett



  1. Hey Bryan – Your readers may be interested in a podcast episode we did on Furnace Filters. Check it out at

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