One of the last things people tend to think about when building a new PC is the airflow going through their case. Believe it or not, but this is a fundamental, and pretty crucial aspect of your build - it just happens to be less exciting than arranging your other specs like your CPU and GPU. If you're building a gaming PC, it might help you to know the differences between positive and negative pressure.
Pro tip: Most PC fans have some handy arrows on them to show you which way the fan will spin, and which direction air will flow through it. Most of the time, you can also see a plastic frame on the back of a fan, which will indicate that air will flow out of that side.
Depending on your experience with building PCs and managing airflow, you may already know that you have intake fans and exhaust fans. Intake fans pull air into your PC, and exhaust fans take air out of it. For those who are unsure, any fan can be an intake or an exhaust fan; it just depends on which way it's facing in your machine relative to the path of the air flowing.
In short, positive pressure is created when you have more air being pulled into your case than is being pushed out of it. Conversely, negative pressure is what happens when you have more exhaust fans than intake fans.
So which of these do you ideally want for a gaming PC's airflow? Well, either can actually work. Depending on your case, its size, and how often you plan on swapping parts, both can suit different users. Both of these create a healthy flow of air in and out of your case, but there are differences you should be aware of.
Ideally, most PC builders will want to configure their airflow so that they have positive pressure. This keeps a healthy supply of air coming into the chassis and ensures that warmer air will actually be extracted through a more direct flow. Negative pressure does have a downside, and it's that air will be pulled through every nook and cranny of your case, which can result in dust building up in the wider mesh panels of your PC case.
Negative pressure may still work for you, though. Technically, Negative pressure is actually superior in cooling a PC. It ensures that hot air is being pulled away from your motherboard and out of your case, which can result in less thermal throttling of one of the best CPUs for gaming. The problem is that you'll also be more likely to have noisier fans as a result.
If you have a smaller case with more mesh panels, it's likely that you'll want to exhaust more warm air since ITX and even Micro ATX cases can be a little quirkier with their airflow setups. Some don't have all that much dedicated space for intake fans, so it becomes more a matter of expelling warm air from a smaller case. Similarly, if you're often swapping parts around, or if you don't mind cleaning regularly, negative pressure won't make too much difference to you.
On the whole, however, positive pressure is what most PC gamers will want to set up in their case so that dust doesn't build up as frequently and they have a direct traversal of air.
Another thing to keep in mind is that if you have an AIO cooler with a radiator, hot air will naturally rise and likely be exhausted through the top of your PC case. That means that you'll be better off setting up positive pressure since the AIO is already doing the heavy exhaust lifting for you.
The thing which a lot of internet forum debates will leave out on this topic is that if you're looking to add more fans to the bottom of your case, your graphics card will naturally exhaust any heat out of its underside, but if you want to configure bottom fans as intake fans, that could create a void in the bottom section of your case. If you're building your own PC, experiment with the fan configurations in your chassis and see what works better for you. If you're getting too much heat or performance issues, maybe flip to the other type of pressure and see if that helps. Remember, for most players, we'd recommend positive pressure, though.
For more gaming PC expertise, check out the best RAM for gaming, the best SSD for gaming, and the best computer speakers.
