In order to properly cool your PC and its components, a good airflow setup is a necessity. Most pre-built PCs come with lousy airflow, thus heating up your components rather quickly. The use of fans is very important, and so is the location and orientation of the fans.

This thread is for ATX cases only.

Here is a proper airflow setup.

• Front: Intakes
• Bottom: Intakes
• Side: Intakes (usually, read below for more)
• Top: Exhausts
• Rear: Exhausts

In some situations, you might need the side fan(s) to exhaust air out of the case. You only want to do this if you are using certain video cards that exhaust heat to the side, such as the 9800GX2 or GTX 295. This is less of an issue with the GTX 295 since the fins on the side of it are pointed to the rear of the chassis.


As you can see, the front fan takes in air since it is low. Cool air is heavier so it stays lower, hot air is lighter therefore it rises. If you have a case like the Antec 1200 where the front fans reach up near the top of the case, they should still be intakes, so you can have positive air pressure.

As I said, cool air is heavier so it remains lower. This is why you want your bottom fan(s) to intake air from outside the case and blow it all around the case.

Once again, hot air rises, therefore top fans should automatically be exhaust fans. Same goes for the rear, since they are positioned right next to the CPU which is pretty high up (except for BTX configutations). Plus, most after market heat sinks direct heat to the rear fan, and take cool air from the opposite side.

Lets get more advanced. If you use some internal fans such as the two in the hard drive cage of the CM ATCS 840 case, or a similar configuration, they should blow air around the case as well. External air ducts should exhaust heat, since dual slot video cards exhaust heat out of the case.

You also want your PSU fan (if it has one on the top of it) to face open ventilation. This is because PSU fans blow air over the PSU components, and the air is then exhausted out of the case. Lots of cases don't have proper ventilation for the power supply. But if your PSU is on the top of a case, it should face down in order to exhaust air, acting as a top exhaust fan.

If the top fans are too close to the front of your case, then you don't want them exhausting air. They would draw out air prematurely before it gets to cool your CPU and video cards. You wouldn't want them intaking air either - this can disrupt the airflow in your case and increase dust. Therefore it is best to not use any fans in such spaces.

What About Air Pressure?

The air pressure of a case matters as well. You can have positive air pressure, neutral air pressure, or negative air pressure.

Negative Air Pressure

Negative air pressure is probably the most common. It should really be avoided. In order to have negative air pressure, you must have more exhaust power than intake power. As a result, air is passively drawn in through open slots and ventilation. This would bring in more dust, and make it harder for video cards to exhaust air since the flow of air is going against it.

Positive Air Pressure

Positive air pressure is not as common in computer cases, but it is the preferred method of cooling. In a positive air pressure system, you must have more intake power than exhaust power. As a result, air passively leaves the case through open slots and ventilation. This reduces the amount of dust in the case, and it makes it easier for video cards to exhaust air since the flow of air is going with it.

Neutral Air Pressure

Neutral air pressure means you have equal intake power and exhaust power. This is a better method than negative air pressure. In a neutral air pressure system, there is less air passively moving into and out of the case. Overall I still prefer positive air pressure, because video cards can exhaust air easier which is vital for Fermi owners such as myself.

Advanced Configurations

With multi-GPU setups, especially NVIDIA's GTX 400 series, you may have to get creative with the airflow in your case. One of the cheapest yet most effective options is channeling air to your video cards. This can be done with simple plastic air ducts. Take a look at the Cooler Master HAF-X case for good examples of this.