# Tech's need help re:computer fan **URL:** \ **Category:** Factual Questions\ **Created:** [May 28, 2002, 2:45am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122 "2002-05-28T02:45:13Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Khadro](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Khadro](https://boards.straightdope.com/u/Khadro)\ **Post date:** [May 28, 2002, 2:45am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/1 "2002-05-28T02:45:13Z")
I will post this so you can get an email saying you have an answer. Then you will visit, see that your question was eaten, and ask it again. Then we can answer it for you šŸ™‚ ---
**Author:** ![Khadro](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Khadro](https://boards.straightdope.com/u/Khadro)\ **Post date:** [May 28, 2002, 2:45am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/2 "2002-05-28T02:45:13Z")
I will post this so you can get an email saying you have an answer. Then you will visit, see that your question was eaten, and ask it again. Then we can answer it for you šŸ™‚ ---
**Author:** ![Khadro](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Khadro](https://boards.straightdope.com/u/Khadro)\ **Post date:** [May 28, 2002, 2:46am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/3 "2002-05-28T02:46:25Z")
I will also post twice, so that I can remember to get emails sent to me letting me know you have re-asked the question. Yeah, that sounds like a good reason. ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [May 28, 2002, 2:51am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/4 "2002-05-28T02:51:06Z")
Server evidently swallowed the OP during the previous 45 minutes of ā€œCannot Find Pageā€ crisis. :rolleyes: Idiot hamster, doesnā€™t it know by now to get the prescription for dexies refilled _before_ Walgreenā€™s closes? šŸ˜ƒ Manny, care to restate? ---
**Author:** ![MannyL](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MannyL](https://boards.straightdope.com/u/MannyL)\ **Post date:** [May 28, 2002, 2:51am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/5 "2002-05-28T02:51:29Z")
Well the question didnā€™t get eaten. I hit submit then the page timedo ut. My original question was -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ I tried google but couldnā€™t find this. I remember seeing on an overclocking site someone posted a way to make a filter at home to help reduce the amount of dust that fans blew into your system. I rememer they used the AC filters cut to size but I donā€™t know if it was put before the fan or after the fan Example (outside case)filter[inside case] or (outside case)fan[indside case] Also what type of AC filter do you use? And Mods if this somehow becomes a dupe please kill the dupe and not this one ---
**Author:** ![Wikkit](https://avatars.discourse-cdn.com/v4/letter/w/c0e974/32.png) [@Wikkit](https://boards.straightdope.com/u/Wikkit)\ **Post date:** [May 28, 2002, 5:22am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/6 "2002-05-28T05:22:14Z")
It depends on your needs. Either will work. You need a set path for air through the computer. An old Mac clone I have has an exhaust fan on the power supply and a tiny fan inside the case that blows at the processorā€™s heat sink. The power supply fan creates a negative pressure inside the case, so air has to get in somewhere. Since they didnā€™t design a vent for it to come in, it sucked air through the floppy drive and CD-ROM, making them the filters. Both drives died within a year. Anyway, the point is that you need a place for air to get in the case and a place for air to get out of the case. You want to filter the air before it gets inside the case. You want the case at positive pressure so that the drives arenā€™t acting as air filters. So, flow schematics. Air flows from left to right: filter -\> case -\> fan -\> through computer -\> exhaust vent or filter -\> fan -\> case -\> through computer -\> exhaust vent are the simplest and most efficient designs where the air filter is outside the case so that it can be easily changed. If it already has an exhaust fan on the power supply, youā€™d want to go: filter -\> case -\> fan -\> through computer -\> power supply fan -\> exhaust vent If your environment isnā€™t that dusty (then why are you bothering?) and you donā€™t mind needing to open the case to clean the filter, then go: case -\> filter -\> fan -\> through computer -\> exhaust vent Pretty intuitive, really. ---
**Author:** ![Encinitas](https://avatars.discourse-cdn.com/v4/letter/e/ee7513/32.png) [@Encinitas](https://boards.straightdope.com/u/Encinitas)\ **Post date:** [May 28, 2002, 6:36am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/7 "2002-05-28T06:36:47Z")
Oh Jeez. I thought this was about Techā€™s needing help with a computer **fan** atic. Never mindā€¦ ---
**Author:** ![MannyL](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MannyL](https://boards.straightdope.com/u/MannyL)\ **Post date:** [May 28, 2002, 5:22pm UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/8 "2002-05-28T17:22:25Z")
> [@](#): > > \*Originally posted by Wikkit \* > [So, flow schematics. Air flows from left to right: > filter -\> case -\> fan -\> through computer -\> exhaust vent > or > filter -\> fan -\> case -\> through computer -\> exhaust vent > > are the simplest and most efficient designs where the air filter is outside the case so that it can be easily changed. > > If it already has an exhaust fan on the power supply, youā€™d want to go: > filter -\> case -\> fan -\> through computer -\> power supply fan -\> exhaust vent > \*\* I have the computer on a desk so itā€™s off the carpet. There is a fan on the bottom front sucking air in. There is a fan that I added in front of the drive cage blowing air oiver the drives. The drives a 4 7200rm drives that get very hot. Every few weeks I notice white ash like dust caked on the drives and the fan that I have to clean off. On the CPU I have two Fans (Itā€™s a slot A athlon) Behund the CPU I have a case fan blowing air onto the CPU. Right above this fan is the Power Supply that is blowing warn air out. In the very top of the case I cut a hole and have a fan blowing air out. Iā€™m tired of cleaning the dust off the drives and I know the dust is making them hotter. ---
**Author:** ![Wikkit](https://avatars.discourse-cdn.com/v4/letter/w/c0e974/32.png) [@Wikkit](https://boards.straightdope.com/u/Wikkit)\ **Post date:** [May 29, 2002, 2:44am UTC](https://boards.straightdope.com/t/techs-need-help-re-computer-fan/111122/9 "2002-05-29T02:44:37Z")
A filter in front of the bottom front fan should do it, if thatā€™s where all the air is going into the case.