# Case fans, how many intake, how many exhaust?



## random100 (Mar 17, 2014)

Currently my computer build has two intake fans on the lower front of the build, and two exhaust fans, one on the top, one on the rear of the build. I have a spare fan slot on the side and it got me thinking, could an extra fan go there? Did a bit of searching on the balance between intake and exhaust fans, what do you think? More intake fans? Or more exhaust fans? Or a balanced amount... what would be the best for cooling and slowing dust intake?


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## bassfisher6522 (Jul 22, 2012)

The only sure way is to run each configuration and check the temps for each configuration then compare the results. It's not easy to say positive pressure is better then negative pressure or balanced. Because each build layout is different...not everyone uses the exact same case and components...so air flow will be different.


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## WereBo (Apr 5, 2008)

Hi raqndom100 :wave:

As my colleague above says, it's mostly trial-&-error whether it's cooler with a side-fan blowing in, sucking out or left off entirely.


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## Tyree (May 10, 2009)

First, are you experiencing any heat issues?
As noted above, basically experimentation.
1x 120mm in front (blowing in) and 1x 120mm in the rear (blowing out) is usually sufficient. Side fans can disrupt the desired front to rear airflow.


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## GZ (Jan 31, 2010)

Just to add to the excellent advice already given.

The side port fan mount on cases can vary in function depending on the case and it's location relative to the mother board.

The best way I can tell you to glean the location of the side port fan mount is by having the case side installed and peering through the fan opening and noting which component you see.

Many smaller cases (mid towers and smaller) have a side opening located in the vicinity of the CPU. This is usually to allow cool air to be funneled directly over the CPU heat sink in cases that have low interior volume and are more subject to high case ambient temperatures. Unfortunately, depending on the manufacturer and layout of the board installed, the CPU can vary in location by quite a bit and render that type of opening nearly useless.

On many "gaming" or "enthusiast" cases there can be one or more fan mounts on the side cover. Most commonly it will be located over the expansion slots where a large video card can effectively create a dam and prevent air from moving in the front-to-back bottom-to-top pattern that is generally recognized as the most efficient airflow pattern inside a computer case. In this type of configuration, the fan can be placed in either an intake or exhaust position and requires a bit of testing to find the way that best suits your particular hardware setup.


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## Tyree (May 10, 2009)

Again, experimentation. Side fans, and sometimes top fans, commonly cause turbulence and disrupt the desired front to rear airflow.


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