Why do people often install fans in the case so that there is positive pressure?

Despite using PCs for decades, have you ever heard the term “positive pressure” when installing a computer case?

Those who are new to PC builds are very likely to encounter the term “positive pressure”, this is the state that professionals often aim for when installing fans, optimizing airflow for the case. So what is “positive pressure” and why do people tend to go for positive pressure? We invite you to find out in the following article.

A case is said to have positive pressure when the air pressure in the case is greater than the outside air pressure. Suffice it to say, the condition for a case to achieve positive pressure is that the amount of air sucked in by the fan must be greater than the amount of air blown out by the fan.

However that sounds complicated so it’s hard to remember. To make it simpler, you install the fan so that the number of fans sucking air in is more than the number of fans blowing air out, then positive pressure is achieved (provided that it is the same type of fan and rotates at the same speed).

For example, my house has a case and I have 3 fans, I attach 2 exhaust fans to the front of the case and the other one blows air out on the back. Simply put, my tank has positive pressure. You can also increase the rotation speed of the inlet fan and decrease the speed of the exhaust fan for a larger pressure difference.

Contrary to positive pressure, we also have negative pressure. That is, when the pressure in the case is less than the outside pressure, the amount of air flow according to the fan entering is less than the level being blown out by the fan.

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In fact, the pressure difference between the air inside the case and the outside of the case is very small.

The maximum differential pressure in the case cannot exceed the static pressure that the case fan can generate. Meanwhile, a huge fan like Noctua’s NF-A14 industrialPPC can only produce a static pressure of over 10mm H2O, which is equivalent to 1/1000 of atmospheric pressure (can be considered as atmospheric pressure). air pressure outside the case).

From this, it is inferred that an NF-A14 industrialPPC fan case cannot have a pressure difference of more than 1/1000 compared to the ambient pressure.

When the pressure is positive, the dust will be removed. The reason is that the air will only enter the case through the exhaust fan and exit all the other ways (eg PCIe slots and the crevices of the case). For case models with a dust filter, positive pressure will be very beneficial because we can assemble a fan set at the place of the dust filter, forcing the air to pass through this filter before going inside. Since then the case will be dirty longer, less frequent cleaning and therefore also live longer. This is why it is common to install fans so that the case has positive pressure.

For a case with negative pressure, even if there is a dust filter, it will get dirty faster than a positive pressure case. The reason is because the air only goes out through the exhaust fan and enters all the other ways, so the dust filter will be greatly reduced.

For case models that do not have a dust filter, you do not need to care about negative or positive pressure because dust will come in anyway. Instead, cleaning to keep the house tidy and less dusty will help the case to be less dirty.

There is a fairly simple case pressure test trick that you can turn on the machine and then burn an incense stick, put it close to the PCIe slot, if smoke is sucked in, it is negative pressure, if smoke is blown out, it is positive pressure. .

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Some technologists tell each other that in a negative pressure case, the air in the case will be a bit cooler than a positive pressure case. However, this view is only true when you use a water cooler and the water rad blocks the air intake. At that time, if the case pressure is positive, all the air that wants to enter your case will have to go through the water rad so it will be hotter. If the pressure is negative, the cool air will follow other routes into the case, so it will be cooler in general.

For a case with an air-sink, whether it’s hot or not depends on how fast the case’s gas exchange rate is. The more cool air the case draws in and the more hot air it releases, the cooler the air in the case will be. And the cooler the air, the more efficiently the air cooler in the case works, from which components such as CPU, GPU, RAM, SSD, chipset… will also be cooler.

Above is an article about positive pressure in a PC case and some interesting information related to it, hope you guys find it useful. Thank you guys for reading.

According to GVN360

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