It’s a well-known natural process for air to flow from high to low pressure. Examples of this are found around us every day. Wind and weather are formed from the uneven heating of the earth’s surface which generates pockets of high and low pressure air. If you’ve ever witnessed the sudden closing of a door as air is sucked out of a room where no breeze was felt, what you experienced was the high pressure air moving to a low pressure area to achieve stasis.
High and low pressure, or positive and negative pressure, can be used as a tool in cleanroom environments to protect against entering contaminants (in positive pressure cleanrooms) or contaminant leakage (in negative pressure cleanrooms). We’re going to focus on negative pressure cleanrooms, how they work, and how they are especially important in some medical cleanroom applications.
What are Negative Air Pressure Cleanrooms?
In a cleanroom, pressurization can be achieved using airflow and air direction. Negative pressure cleanrooms exhaust more air than they supply to create a lower pressure than is found in the surrounding rooms. Negative pressure in cleanrooms is useful because it prevents any contaminants or hazardous substances inside the cleanroom from leaking out where they could contaminate adjacent rooms or endanger employees.
Negative pressure is used in sensitive applications where processes or substances within the cleanroom could be hazardous to work or health outside. Negative pressure is a simple way to further limit the possible escape of harmful particles, fumes, or substances, when used effectively with proper filtration and adequate ventilation.
How Negative Pressure Cleanrooms Work
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 air will want to flow into the cleanroom to fill the low pressure area, effectively stopping contaminants from going against that natural movement in order to escape the cleanroom.
In order for the negative pressure cleanroom to work, adjacent spaces must be maintained at a higher pressure than that of the cleanroom. A slight difference in pressure will prove effective at limiting contaminants, but the greater the pressure differential, the stronger the force of air that wants to move to achieve equilibrium, and thus the greater the resistance for contaminants to move the opposite direction. However, it is possible to have pressure that is too negative, as this could force contaminants into the cleanroom, where they could be detrimental in some applications.
Some cleanrooms only require a slightly negative pressure in order to contain aerosols, while others require a higher pressure difference to aid in containing hazardous liquids or gases from transferring in pass-throughs or other access points. Depending on your application, you may choose a higher pressure differential in order to limit the possible escape of hazardous liquids or toxic fumes. In any case, having a pressure monitoring system is important to ensuring balance and consistency within your cleanroom. If you’re exploring negative pressure cleanroom design, it’s a good idea to build in a monitoring system so you can always check and alter pressure as needed.
Determining Where to Use Negative Pressure in Cleanrooms
Negative pressure can be used in a small area, as the total cleanroom pressure, or in part of the cleanroom design such as in a passthrough, workstation, or storage cabinet. An external exhaust removes air and airborne contaminants, odors, or fumes, and prevents hazardous, toxic substances from escaping the negatively pressurized space.
Some cleanrooms require an enclosed space within the cleanroom to be at a different pressure than surrounding spaces. These are known as negative pressure rooms and are commonly found in pharmaceutical or medical research cleanrooms working with hazardous compounds or infectious particles. Negative pressure rooms are an example of a segmented cleanroom, where other segments may meet different classification requirements or have different needs for pressure, cleanliness, or operating procedures.
Medical Industries and Negative Air Pressure Cleanrooms
Negative pressure cleanrooms are particularly useful in medical applications where the work involves hazardous compounds, toxic fumes, or infectious substances. A few examples of medical industries that use negative pressure cleanrooms are hospitals, medical research laboratories, and the pharmaceutical industry.
Hospitals use negative pressure cleanrooms to contain airborne contagions, pathogens, and viruses.
Whether for research, treatment, preventative isolation or quarantine, negative pressure helps seal in dangerous contaminants to keep hospital staff and patients safe. Hospital cleanroom applications that work with hazardous drugs or infectious diseases are often required to use negative pressure when handling products and treating patients.
Medical Research Cleanroom
Medical research, especially that which involves hazardous substances, aerosol contaminants, or toxic waste, is generally done within the confines and protection of a biosafe cleanroom. Negative pressure is used to prevent any harmful particles from escaping the cleanroom where they could contaminate other spaces or endanger human or animal lives. Negative pressure cleanrooms protect researchers by containing hazardous materials or substances within the cleanroom, where staff is prepared with proper gowning and protective equipment.
Pharmaceutical cleanrooms, particularly those that must comply with USP 800 standards for sterile and non sterile compounding of hazardous materials often require negative pressure to operate safely. Negative pressure cleanrooms allow for safer handling of hazardous drugs, presenting fewer risks to employees and consumers. USP 800 pharmaceutical cleanrooms require a dedicated water channel gauge to monitor pressurization, ensuring that the differential is high enough to be effective, but not too high where it could reduce efficiency and potentially bring contamination into critical parts of the cleanroom.
Negative pressure cleanrooms are helpful in cleanrooms where the emphasis is on containing the work, product, or processes within the cleanroom. Although they are particularly useful in many medical cleanroom applications, some negative pressure cleanrooms can be found in other industries where hazardous materials need to be controlled.
Need a negative pressure cleanroom for your sensitive application? At Angstrom Technology, we have the tools and expertise to design the cleanroom that best fits your application and your budget. For a free quote, reach out to our team.