Changing a Furnace Filter

To keep your furnace running as efficiently as possible, it is important to regularly change the air filter. This guide is about changing a furnace filter.


October 11, 2005 Flag
0 found this helpful

I'm hoping someone can settle a dispute between my husband and I. I really just want him to see it in print, then maybe it'll sink in. How often does everyone change their furnace filter during the winter months? He changes ours twice a year and really honestly believes that it is often enough. I say it should be every month during November to April. What do you think? I'll show him all responses.

Thank you.
Sandy from Pittsburgh, PA

Anonymous Flag
July 6, 20100 found this helpful

When I bought my furnace, they told me to change the filter every three months. This past February, the furnace wasn't kicking on. I was about to call a service person, then decided to read the trouble-shooting tips on their website. It said to first change the filter. It was at month 2 at that point, but I changed it. The furnace started working right away. From now on, I will change it every 2 months during the winter.

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January 7, 20130 found this helpful

There is really no standard on when to change your filters, as people have different HVAC systems? My filters are the 3M Merv12 size 16x20x4 & it cost $35-40 a pop at Amazon. If you change that monthly, or even bi-monthly, it will cost hundreds of dollars a year. Get real.

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April 18, 20130 found this helpful

It really depends on the type of filter you are using. Some should be changed once a month while others should be changed once every three months. There are also a variety of air filters out there including: HEPA, Ionic, Carbon and UV Light. For more information, check out this article: ... nsurance/change-home-air-filter.aspx

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January 12, 20151 found this helpful

Keep in mind: It is a complete myth that when a partially clogged filter begins to slow down the airflow, the fan will "work harder to try to maintain airflow". Fans don't try to maintain airflow. They have no will. In the real world, squirrel cage fans actually work harder when they are moving air freely. If you completely block the airflow, the fan will spin faster because it's easier to just spin the air around in its chamber than to move large quantities of air. It doesn't spin faster because it's "trying harder". There are good reasons to change filters, but saving electrical energy from fan use is simply not one of them.

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Anonymous Flag
April 11, 20160 found this helpful

April 18, 2011 Flag
1 found this helpful

I could never remember for sure when I changed my A/C furnace filter, so now I write the date I need to replace it on the filter with a permanent marker. Works great! No more trying to remember!

By Barbara from Columbia, KY

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April 18, 20110 found this helpful

Then I write the "change" date on the fridge calendar to remind myself again!

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December 26, 2014 Flag
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I live in a mobile home and have a Coleman heat and air unit; it is all electric. My home is very dusty, yet every time I change the filter there's not a speck of dust on it.

By Pamela

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December 26, 20140 found this helpful

Your furnace filter will only catch dust that is easily airborne. Most dust is too heavy to make it up to a furnace filter and just settles on the floor, furniture, etc. Your couch and upholstered chairs become very dusty as people often do not realize their couches, beds, etc., are huge dust collectors. They do not vacuum their furniture as they do not "see" the dust. Then, when people sit down on couches, beds, etc., dust from the furniture will rise in billowing clouds and will then settle on surrounding furniture and floors.

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December 28, 20140 found this helpful

I don't think your fan is working properly. Is it heating well? My filters are always covered with dust, and the fan itself will get clogged with it. Turn your furnace off and check to see if the fan is clogged.

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April 10, 2008 Flag

Save on heating/cooling costs by maintaining your air filter. A heating system repairman told me to use the cheapest, blue filter, and to change it at least monthly or when soiled. He told me this would let the air conditioning motor work much more easily, saving electricity and extending the life of the air conditioner.

If you have a 14x20 inch opening, you can buy a 30x20 inch filter and make 2 from them. Get the wire-supported corrugated white filter. Cut the supporting cardboard at 15 inches. Cut the filter to size, and fold the cardboard supports back 1 inch to support the filter. Make sure the edge meets the opening. Now you have 2 filters.

By Nance from Statesboro, GA

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April 11, 20080 found this helpful

PLEASE, consider WHO told you to use the cheapest filters. It's NOT a good idea to cut corners in that area because it allows too much dirt and dust into your system,as well as your home, thereby shortening the furnace's life and giving the furnace company more repeat business.

More dust/dirt into the atmosphere of your home is unhealthy, and it WILL take it's toll on your health sooner than you think. Cut corners some other way, unless you have no other choice, because you WILL make up the difference between the cheapies and the better FILTRETE filter, as an example, cost by SAVING RX, over the counter MEDS, and trips to the doctor because while your body was having to work overtime to fight the pollution you've forced it to breathe, it's immune system is compromised and weakened so that you are more easily able to get ill. Don't go whole hog and buy the VERY expensive filters, but don't settle for those blue thin useless ones either, regardless of who claims they're "just fine". Although they do filter SOME particles/ dust/ pet hair, etc. over time, the mid-range accordian pleated white filters are about ten times more effieient at filtering harmful bacteria and viruses from the air. You should reconsider and bite the bullet for a wiser choice that should cost around $5.99 for most sizes.

Good luck and God bless you,


Richardson, TX

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April 11, 20080 found this helpful

Get in the habit of changing the filter when you pay the house note (or utility bill).. after two or three times, it's 'automatic' :)

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January 4, 2014 Flag
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My furnace filter is between the furnace and the humidifier. The filter is installed upright. Should the arrow point to the furnace or to the humidifier? I don't know where the furnace blower is.

By Jean H.

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January 8, 20140 found this helpful

The arrow goes in the direction of the air flow.

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April 3, 2011 Flag
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I don't know how to change my furnace filter. What do I do?

By Sharon from Cudahy, WI

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April 3, 20110 found this helpful

Check out the following website, use their search box at the top.

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Anonymous Flag
April 4, 20110 found this helpful

There's a 'door' on one of the sides of the furnace itself. Open that and you'll easily be able to figure out how to slide the filter out. Check the measurement written on the filter edges so you'll know exactly what size to buy to replace the old one.

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June 18, 2004 Flag
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To save on your electric bill and to make your air conditioner compressor last longer, keep your furnace filters clean. We put a post-it note on the furnace door with the date we last cleaned them. By Terri H.

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