Cleanrooms Air Pressure Differences
If you’re considering a cleanroom, you’re probably trying to gather as much information as possible. What type of cleanroom is right for you? What industry standards do you have to meet? Where will your cleanroom go? You get the picture. Well, one piece of information that might be useful to you is understanding the difference between positive and negative air pressure cleanrooms. As you probably already know, airflow plays a leading role in keeping your cleanroom to standard, but what you may not have known is that air pressure can have a big effect on that as well. So here’s a broken down explanation of each positive and negative air pressure.
POSITIVE AIR PRESSURE CLEANROOMS
This means that the air pressure inside your cleanroom is greater than the pressure outside of it. This is achieved by pumping clean, filtered air into the cleanroom, generally through the ceiling.
Positive pressure is used in cleanrooms where the priority is keeping any possible germs or contaminants out of the cleanroom. In the event that there was a leak, or a door opened, clean air would be forced out of the cleanroom, rather than unfiltered air being allowed into the cleanroom. This works somewhat similarly to deflating a balloon; when you untie a balloon, or pop it, air rushes out because the air pressure in the balloon is higher than the pressure of the ambient air.
Positive pressure cleanrooms are used primarily for industries where the cleanroom functions to keep the product clean and safe from particulates, like in the microelectronic industry where even the tiniest particle can damage the integrity of the microchips being manufactured.
NEGATIVE AIR PRESSURE CLEANROOMS
In a negative air pressure cleanroom, the air pressure in the room is lower than the pressure outside of the room. Generally this is achieved by filtering air out of the room. In most situations, air enters through filters near the floor, and then is sucked out through filters in the room ceiling.
Negative air pressure is used in cleanrooms where the goal is to keep any possible contamination from escaping the cleanroom. Windows and doors have to be completely sealed, and by having a lower pressure, air outside the cleanroom is likely to flow into it, rather than out of it. Think of it like an empty cup that you set in a bucket of water. If you push the cup into the water rightside up, water flows into the cup, because it has lower pressure than the water. The negative pressure cleanroom is like the empty cup here.
Negative air pressure cleanrooms are used in industries that manufacture pharmaceutical products, do biochemical testing, and also in hospitals to quarantine seriously contagious patients. Any air that flows out of the room has to first flow out of a filter, ensuring that no contaminants can escape.