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Intake And Exhaust cooling

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Nov 5, 2003
Intake And Exhaust case cooling

I need abit of help again please :)

I've bought two more case fans for intake and exhaust I believe..
2x 80mm Coolermaster Neon Blue LEDs fans, I was just curious to know how to install these?
Well I know how to put them on etc.. but which way is the air supposed to flow?

Is this set right?

Rear fan.. I feel air coming out of the case from the fan... is it meant to be blowing into the case? or is that correct?

Front fan.. the air is blowing like.. out of the front of the case well kinda.. well the air is blowing outwards anyways on both fans..

Is this correct?
Last edited:


Mar 30, 2003
no, usually the front fans are "intake" or should be blowing into the case while the exhaust is what you have, blowing out.


Nov 5, 2003
stan03 said:
no, usually the front fans are "intake" or should be blowing into the case while the exhaust is what you have, blowing out.

so i just need to flip my front one yeah?


Jun 20, 2003
Shallotte, NC
Here is a good read:

Maximus Nickus said:
Air-The Basics

The basic theory behind any cooling is to remove hot air particles and draw cooler air particles in, this is normally achieved by exhausting the hot air out of the back and top of the case and drawing cooler air in through the front. However there are many variations on this, now that I’ve explained the basic principal lets get on with it.

Air intake and vents

Anyone can stick a fan into the front of a case but positioning it to be effective is rather tricky, most vents in the front of PC’s have grills over them. This not only creates a whining noise with high power fans (due to the buffeting) but it also reduces airflow by as much as 65%.
Simple one this is though: simply take a pair of pliers and go around the edges till the grill falls out, once it’s removed you can sand down the edges to make it smooth (Careful, the edges are very sharp) but you cannot see it from the outside in most cases so it may not be worth the extra work of stripping down the case.

Now every front intake is positioned differently, whether it’s right at the bottom, or in a drive-cage it all makes a difference on airflow characteristics as well as which sort of fan you should use - Experimentation is the key.

Hence if there is only one intake you will want to make the most of it, you could either cut a 120mm intake with a Dremel, or simply use a high power 80mm fan. Depending on where it is placed can also affect this decision. If the fan is blowing directly on your CPU you may wish to use a slightly more potent fan than originally intended to provide that “extra” bit of airflow.

Another concern is Dust, regardless of case pressure (explained later in this thread) dust will accumulate, it insulates heat and causes less and less air to circulate through the PC, and is a mammoth task to clear up, so what are the solutions?
Basically I would use a homemade dust guard, something like a stocking, (Yes I know, no funny thoughts please!) placing this at the front of the case in front or behind the intakes (depending on which is more accessible for cleaning) will trap the dust but still maintain good airflow, obviously you want a compromise between air and dust, try out different combinations and monitor your temperatures.
Every system puts out different amounts of heat in different places so its really trial and error to get the best setup for your rig, just be patient and DON’T rush things.

Heres a great tip to maximize the use of airflow in your case, all you need to do is the following:
You will need 1 sheet of see-through glass or plastic the size of your case panel, and 1 incense stick.
Simply replace the side of your case with the sheet of plastic/glass and put the incense stick in front of the PC (not to close…do I smell burning!?) and watch the smoke move around your PC, this allows you to see “hot-spots” and other problems with your airflow.


There are many types of exhausts, from regular fans to PCI card blowers, they are all designed with one thing in mind, but are used for slightly different effects.
One thing to remember is the positioning of your exhausts, you want then as near as parallel to the intakes as possible to enable the most efficient airflow without any blockades, a common mistake is to put them in a cluttered area where they cannot “breath”, this causes very little airflow and makes that distinct whining sound.
I would position a PCI a slot blower under the AGP card (if there are no available fan apertures) coupled with a exhaust under and above the PSU, this should provide steady airflow.

Now, remember those good old science classes? When you were taught about convection, radiation and conduction? Remember how Hot air particles rise? Then there is no point in fighting gravity (who would win? :D) so exhausts at the upper level of the case are very effective at removing “hot spots” (spots around crowded areas usually in the top of cases, around the PSU and around cables where the temp steadily increases due to the absence of airflow) and exhausting hot air.


When building an effective cooling system you have to take into account the affects pressure has on a case, positive pressure (more airflow entering) will create a pressure of cool air and less dust will accumulate, however negative pressure (more airflow exhausting) with be exhausting more air than is available and thus as a result increases the dust level.
Therefore positive pressure is often the most preferred.
To achieve this simply have more air arriving than leaving!

This came from Maximus Nickus's "Cooling-The Definitive Guide" sticky at the top of the Cooling page. I would suggest reading the entire sticky as it is well worth your time and covers all the basic's of cooling.

Hope this helps.