What is the positive and negative air pressure in the pc

A common solution to increase the longevity of PC hardware is to create and maintain optimized airflow within the case to reduce the overall temperature of internal components, such as the CPU and GPU, and prevent overheating.

This also allows you to safely overload the CPU at higher speeds, thus reducing the need to upgrade to a faster CPU for a longer period of time.

To make things as simple as possible, a box can have one of these 3 air pressures:

Positive pressure. Negative pressure. Neutral pressure.

As a first step, it is crucial to decide what type of pressure system we want to achieve, since this determines the type of fans to buy, as well as their position inside the box. All three pressure systems have their advantages and disadvantages.

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Positive pressure is achieved when there is greater CFM (cubic feet per minute) of air from the inlet fans than from the outlet fans. Positive pressure produces less dust inside the box , as air is expelled through all openings, regardless of size, due to excess. However, this method provides less cooling for a longer period of time, as the hot air pockets remain trapped within small nooks.

Negative pressure works backwards: the CFM of the exhaust air exceeds that of the intake air, thus creating a partial vacuum inside the box that eliminates hot air pockets. This type of pressure amplifies natural convection and provides better cooling at the cost of additional maintenance required to clean up dust. In addition, the air flow works in tandem with the direct output of the graphics cards, since they also release hot air inside the box.

What is pressure and how to measure it

On overclocking forums, there are often discussions about which type of pressure is best in terms of cooling or cleaning. To begin with, pressure is the pressure coefficient of a box, determined by the ratio of the volume of air moving inside the box to the volume of air moving outside the box.

The pressure cannot be determined by the mere number of fans. For example, a simple 230mm inlet would move more air than 2x 80mm outlet, creating a positive pressure in the case, rather than the expected negative pressure when only the number of fans is heard.

To identify what pressure you are currently having, add the specified CFM rating of your individual intake fans (usually mentioned on the fan case or on the motor itself) to your total intake CFM and compare it to the total sum of the output CFM. If the total input CFM consumption is greater than your total output CFM, you have positive pressure in the box, and vice versa.

Please note that the use of filters, dust covers and other obstructions at the inlets reduce the specified CFM, so this calculation method is not foolproof. Therefore, if you are using filters on the inputs, and the input CFM is less than 3 times higher than the output CFM, you could also have negative pressure in the box.

Positive pressure

With positive air pressure you have more air being pushed into the box than air being drawn out. So you have more air pressure inside the box than going out. This method is a good option because less dust collects inside the box because air will try to escape through small openings and holes.

It is often said to be better than negative pressure in terms of dust accumulation and cooling, but positive pressure also has its drawbacks.

Pros

Slower dust build-up: When the inlets are filtered, air may be leaking through the gaps. Atmospheric dust cannot go against air flow, so it is kept out.

Short-term effective: Cold air (comparatively) that blows keeps temperatures low for some time after startup.

Cons

Seriously inefficient in the long term: there is more air entering than leaving. So the air doesn't come out fast enough. That is, it stays indoors longer near the heated components and absorbs more heat, but in the process it heats up other components as it passes over them upon exiting. In narrow, closed, or obstructed spaces, such as between RAM modules, disk drives, GPUs, and in particular the top front of the case, hot air pockets form when the system runs longer, resulting in makes things worse. Although good air flow and good internal cable management can significantly reduce this problem, it cannot completely eliminate it.

Negative pressure

The air that is extracted from the box is more than the air that enters it. This creates a vacuum-like effect inside the box, making it ideal for cooling as hot air is blown out faster. However, the only downside is that the dust will accumulate faster and probably much more compared to other pressures. Unlike positive pressure, negative air pressure will cause air to be pushed into the box through small openings and holes.

This may sound strange, but negative pressure has been criticized many times. To justify this claim, here are its advantages and disadvantages.

Pros

Lower temperature time curve - slower rise in temperatures over a long operating time.

There are no hot air pockets inside: the partial vacuum left by the air leaving the box cannot be filled quickly enough with the filtered inlets and air from other voids. To fill it, the air left around the box begins to move into place, eliminating all air pockets. With this air, if the fans are positioned correctly, cold air is quickly evacuated from the box, absorbing heat from other parts on its way, and the cycle continues.

Cons

Accelerated Dust Accumulation - Many report negative pressure in the event that the rate at which dust accumulates increases. Therefore, a negative pressure case needs to be cleaned more often than a positive pressure case. However, this may be without foundation. For much more dust to accumulate, it would require significant spaces, such as unoccupied fan mounts, open expansion covers, etc., which rarely happens.

How to avoid dust accumulation

Remove the filters at negative pressures for half a month, and see what happens. If the front panel is shaped like a mesh it is one thing, but something different is when it is not filtered. Either way, this is what we do to counter gaps of all sizes:

Get some anti-vibration and noise pads sold in German stores.Cut them carefully and evenly to make them thinner. As thin as possible, but nothing above 3 mm (there are also those measurements). Remove any thick lumps. Trim any stray fibers that stick out. Cut the pad as needed to cover the gaps. Paste it in place.

120mm Dust Filter Computer Fan Filter Black PVC Dust Cover Computer Mesh 10 Packs with 40 Pieces of Screws

This may take a little skill. If you feel uncomfortable doing this, you may want to consider using precut custom cut filters. This inner lining has a triple purpose:

Keep dust out of the box. Acoustic damping.

Neutral pressure

This is probably the most ideal pressure to achieve, but it is quite difficult to achieve because the air pressure inside the box has to be equal to the air pressure outside the box.

Aiming at a slight positive air pressure is recommended as you will achieve close to neutral pressure with less dust problems. This can be accomplished by having a slightly higher CFM on inlet than outlet fans.

However, even if you choose a positive air pressure, you will still receive small amounts of dust that will accumulate inside the box, although to a lesser extent than with a negative pressure.

Proper maintenance

Keeping your PC clean can be a hassle, but it is really necessary. Component longevity depends on how well you maintain your PC, as dust is a silent killer of PC components. So you want your PC to be as dust-free as possible or it won't work as it is supposed to. I would recommend cleaning the computer at least every two months or so.

There is a way to make maintenance as easy as possible: using dust filters. In truth, you need dust filters for your fans because using them will allow you to clean your PC every 3-4 months (depending on the environment where it is located).

Buying a case with dust filters will make cleaning your PC really easy. Filter, dust blower and swabs are all you need for a cleaner PC.

Box structure

The design of your PC case is very important, since it determines the number of fans that can be installed, their positioning and the management of the cables inside the case. The box needs to allow two or three fans to be mounted behind the front panel for the air intake. To extract the hot air we need two fans mounted under the top panel and one fan inside the rear panel. Also, another inlet fan can be installed inside the left side panel.

Fan Selection

The efficiency of the airflow system depends less on the number of fans used than on the CFM rating of the fan itself.

Strive to select a fan with an approximate rating of 45-60-CFM. For positive pressure, place fans with higher CFM capacities on the front and side panels of the case. For negative pressures, place fans with higher CFM capacities on the top and rear panels.

We recommend you read our guide to fans

The size of the fans depends on the specifications of each case. In general, 80, 120 or 140 mm fans are the most used. Smaller ones tend to be noisier, but this is not always the case. Use the opinions of consumers to inform you. However, no matter how many fans you decide to buy, verify that the power supply has enough voltage to support them.

Cable management

Cable management is something you really shouldn't ignore because it can greatly affect the air flow inside the box. Most boxes today have a cable management feature that allows cables to be fed through the back of the box to make the box look nicer and cleaner.

If you don't have a box that has a cable management feature, then you can still do a little cable management using cable ties. Tie bundles of wires that go in a similar area and try to hide them as much as possible to allow air to flow better.

One of the main problems of not handling the cables correctly is the accumulation of dust. Loose cables become anchors for dust to accumulate and dust is the worst enemy of PC components. Fans will also be less effective if dust starts to build up, so keeping your PC well maintained is one way to avoid this problem.

Final Words about what is positive and negative pressure

That's all you need to know to optimize your PC case for the best possible airflow. We hope you now understand the basics of air cooling and what you can do to improve your box airflow.

Using all of the above methods ensures that your hardware will not degrade due to overheating as it is virtually eliminated. CPU temperatures in the 70 ° to 80 ° C range can be controlled, but if we get the whole system around 60 ° C much better .

What pressure do you use on your computer? Positive or negative ? What advice do you recommend to our readers?