Do You Know the Difference Between Negative Pressure vs. Positive Pressure Cleanrooms?

Do You Know the Difference Between Negative Pressure vs. Positive Pressure Cleanrooms?

In today’s fast-paced world of technology, pressurized cleanrooms are being utilized in more and more industries and applications. Two main types of cleanrooms are negative pressure rooms and positive pressure rooms. 

The level of pressure determines the way air naturally moves in a space. High and low, or positive and negative, pressure can be used as tools in cleanroom environments to help cleanrooms reach their required classifications.

Negative Pressure vs. Positive Pressure Cleanrooms

Let’s dive deeper, learn the difference between negative pressure vs. positive pressure cleanrooms, and discover how they work. 

How Does Air Pressure in Cleanrooms Work?

Air naturally flows from areas of high pressure to areas of low pressure. Examples of this are found around us every day. For example, wind and weather are formed from the uneven heating of the earth’s surface, which generates pockets of high and low pressure air. 

Have you ever witnessed the sudden closing of a door as air is sucked out of a room even though there’s no breeze? This experience is high pressure air moving to a low pressure area to achieve stasis. 

Another example of this process is when air escapes from a balloon. The air travels from a high pressure environment to the relatively low pressure of the surrounding air. 

What happens in all of these situations is that when air is moving in one direction, it’s not moving in the opposite direction. When air is moving out of the balloon, air isn’t also moving into the balloon, as long as the air inside the balloon is more pressurized. 

This concept can be applied to cleanrooms to stop airflow into a cleanroom or out of it, limiting particle transfer via the air and maintaining a cleaner environment.

To put this as simply as possible:

Higher pressure air within a cleanroom (compared to the air outside the room) blocks contaminants from entering the cleanroom, as air naturally wants to flow out. Conversely, lower pressure air within a cleanroom can trap contaminants and prevent them from leaving a cleanroom, as the natural flow of air wants to move in. 

Using Positive and Negative Pressure in Cleanroom Design

Using pressure in cleanrooms, either high pressure (positive pressure) or low pressure (negative pressure), can benefit many cleanroom applications, but how do you implement it in the cleanroom design?

Cleanroom pressure is achieved by controlling how much air is put into the cleanroom and how much is withdrawn. 

In a positive pressure cleanroom, filtered air is consistently pumped into the room through the HEPA filtration and cleanroom HVAC system. If a door or window were opened in the cleanroom, air would rush out into the outside environment. This positive pressure ensures that the products and processes within the cleanroom are protected in the event of a breach or leak. Because the cleanroom has positive pressure, the air is forced out of the cleanroom, preventing contaminated or unfiltered air from seeping in. 

To achieve negative air pressure, external exhausts pull air from the cleanroom at a faster rate than air is introduced over a span of time. The resulting negative pressure means the air will want to flow into the cleanroom to fill the low pressure area, effectively stopping contaminants from going against that natural movement to escape the cleanroom.

To maintain positive or negative pressure in cleanrooms, adjacent spaces must be maintained at a lower or higher pressure than that of the cleanroom. If you implement a pressurization system into your cleanroom design, a pressure monitoring system is vital to ensure balance and consistency. The monitoring system will check and maintain consistent pressure, which can be adjusted manually or automatically.


High pressure, or positive pressure rooms are beneficial in applications where the slightest particle interference could disrupt processes within the cleanroom. 

Semiconductor cleanrooms, microprocessor cleanrooms, and aerospace and defense cleanrooms are examples of industries that benefit from positive pressure cleanrooms, as they are highly averse to contaminating particles. Medical cleanrooms also use positive pressure to protect sensitive patients and maintain a controlled space.

Even when the stakes aren’t as high, using slightly positive pressure in cleanrooms can help reach cleanroom classifications and maintain an overall cleaner environment.


Low pressure cleanrooms, or negative pressure rooms, are ideal for applications that need to isolate substances, particles, or fumes inside the cleanroom environment to protect the space outside. They are widely used in medical cleanrooms for research, testing, and the development of treatments using sensitive substances. 

Pharmaceutical applications also use negative pressure in cleanrooms as part of a segmented layout. One room is kept at a lower pressure, while the anteroom immediately outside is maintained at a slightly higher pressure. This allows employees to transition into the negative pressure room with minimized disruption.

Need Help Choosing the Right Cleanroom Pressure? Angstrom Technology Can Help

Using the natural air movement due to pressure, we can build safer, more effective cleanrooms. Positive and negative pressure cleanrooms can protect against entering contaminants (in positive pressure cleanrooms) or contaminant leakage (in negative pressure cleanrooms). 

Which cleanroom pressure best suits your needs? At Angstrom Technology, we’re here to guide you. Our dedicated cleanroom experts are ready to precisely tailor airflow patterns and containment solutions for your unique application. Get in touch with us today for expert assistance in creating the ideal cleanroom environment for your specific requirements.