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Manage My Life

how do I determine "furnace airflow" ?

ok, so I'm a little dense - or maybe a lot...I took out the old greyish filter and ready to replace with a new one, but now don't know which direction to install it. Do I point the arrow AWAY from the furnace, or TOWARDS the furnace?? Am confused about filtering the air flow , does it mean return air going into furnace or warm air going out? Also a secondary question: does the filter still do its job if it goes in backwards?

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2 Answers from these members:
Manage My Life
I'm sorry to hear that you are having some difficulties with your.Furnace filter replacement. I did some research for you at and found an excellent article that may help until your expert can respond to your specific question. The link is attached below. Don't worry we all get confused on this.
by Manage My Life
November 16th, 2011
Answered in 21 minutes
0 votes
Sam A
Thank you for you question on the airflow of the replacement for the filter.

You will point the arrow towards the furnace since the air is returning to the furnace.

A little more detail for your information.

The direction is only critical if the filter you are installing is structurally built for airflow to go the same direction of the arrow so the force of the airflow will not collapse the filter.

In most standard glass web air filters the directions is not critical. Just be careful to not crush the cardboard on the filter when installing it.

I hope this will help.

Sam A.
by Sam A Earned 1,714 community points in Building Supplies
November 16th, 2011
Answered in 2 hours
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