Furnace filter?

This may sound like a dumb question, but it's been bothering me for quite a while. Our forced hot air furnace/AC unit in the basement has a fan at the bottom. Filters (those carboard/blue things - ours is 16x25x1) are placed between the fan and a large duct. The filters have an arrow on them that show how it should be placed - given the direction of the airflow. Only problem is, is that I don't know the direction of the airflow. Does it flow from the fan to the duct or from the duct to the fan?
TIA, Sandy K.
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Usually filters are placed as close as possible to the intake of the fan, which is usually at the end of the return duct, so the arrows should point towards the fan.
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Not a dumb question at all. My new house had 2 AC/Furnaces. They had non descript filters without arrows when I moved in. I basically looked at the ductwork and realized that the returns were coming down adn going to the main unit and the filter was in between the two. Therefore I put them in with the arrows pointing towards the main unit. I also figured that while air quality is important, Carrier would want to protect their equipment from the dirt and whatnot, so it would probably be before the main unit. Hope that makes sense...it did to me when I first started writing it. :-)
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Not a dumb question at all. My new house had 2 AC/Furnaces. They had non descript filters without arrows when I moved in. I basically looked at the ductwork and realized that the returns were coming down adn going to the main unit and the filter was in between the two. Therefore I put them in with the arrows pointing towards the main unit. I also figured that while air quality is important, Carrier would want to protect their equipment from the dirt and whatnot, so it would probably be before the main unit. Hope that makes sense...it did to me when I first started writing it. :-)
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Sandy K. wrote:

Not a dumb question. The filter's main job is to protect the fan and furnace from too much dust. It should be placed before the fan, so the arrow should point towards the fan.
--
Joseph Meehan

Dia duit
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Thanks to all for the replies.
Sandy K.
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Joseph Meehan wrote:

In another word, arrow should point the flow of air. No brainer at all. When I had my house built 10 years ago I insisted on cleaning everything off the floors and walls any dust or fine debris accumulated during construction. Now all I have is an electronic air cleaner catching dust. It's clean house to begin with. Tony
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