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.

Hospital Cleanrooms

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

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.

Even with a powerful HVAC system, a multi-stage HEPA filtration process, and thorough cleaning procedures, contaminants can still threaten a controlled cleanroom environment. Static electricity is common everywhere we live, but in a cleanroom it can be unpleasant, detrimental, and even dangerous. How can the dangers of static affect your application? How can these problems be avoided? Let’s explore static electricity in medical device cleanrooms, and how to build static control into your cleanroom design from the ground up.

Why Does Static Matter?

Static electricity is caused by an imbalance of positive and negative charges on a surface or object. These charges accumulate until they’re neutralized or discharged. It’s a common phenomenon in all parts of the world and is usually harmless. In a cleanroom, however, the buildup of static electricity can be dangerous to products and employees. 

Static electricity in cleanrooms can present dangers to any industry, but in medical device manufacturing, assembly, and packaging it could have disastrous, life-altering consequences. Three ways static can influence with medical device cleanroom safety and efficiency are by:

Attracting Contaminants

Static causes contaminants to adhere to charged surfaces through electrostatic attraction (ESA). ESA can occur in many stages of product development and assembly but is perhaps most dangerous in packaging. Particularly if products are packaged using plastic, they can carry charges that are not neutralized during shipping. Once opened, contaminants are attracted to the device, causing it to fail or be rejected. 

Inhibiting Equipment

Static that accumulates during product development can interrupt important processes. If parts of the device are repelled or attracted to machinery or equipment it can contaminate them or cause a slowdown in operations, reducing your cleanroom’s efficiency and increasing operational costs.

Generating Charges

Static charges that accumulate on surfaces, equipment, personnel, and products that are not properly discharged or neutralized can interfere with electronics or hardware you use to create devices or the devices themselves, causing them to malfunction or fail. Static charges can also create electric shocks, which, while not likely to cause extreme bodily harm, could cause involuntary movement which could lead to accidents or damage to the employee, delicate equipment, or devices. 

Managing static effectively is crucial. Even when the effects of static electricity in medical device cleanrooms are not threatening to the devices you develop, assemble, or package, they may interfere with efficiency and affect operational costs of your facility.  How do you control static in your cleanroom? Many potential problems can be addressed in your cleanroom design and then managed with specific static control cleanroom supplies.

Static Control Methods in Cleanroom Design

Cleanroom design can incorporate methods to conduct, dissipate, or neutralize static electricity.

Conduction

In conduction, materials or surfaces that present little resistance to the flow of electrons are used to guide charges to the ground safely. Conductive materials direct charges away from where they can damage products or attract contaminants. 

Dissipation

Dissipation, similar to conduction, is the flow of charges to the ground, but occurs more slowly and in a more controlled manner. Materials that allow electrostatic discharge through dissipation can be used in flooring, wall materials, and furniture. ESD products discourage the buildup of static electricity to protect products, employees, and cleanroom operations. 

Neutralization

To neutralize static, the imbalance of charges must be corrected through adding electrons to positive charges or removing electrons from negative charges. Air ionization is one method more medical cleanrooms are adopting to neutralize air and surface charges. 

An air ionization system adds positive and negative ions to the atmosphere of your cleanroom, directing them with a focused nozzle or blower. The ions are attracted to charged surfaces of the opposite polarity, balancing and effectively neutralizing the surface. Air ionization systems can be incorporated in key areas of production of medical devices, as well as at entry points of the cleanroom to limit the introduction of charges into the cleanroom by employees.

Static Control Equipment Cleanroom Supplies

To control static electricity and prevent harmful effects including damage to your equipment, employees, and products, anti-static cleanroom supplies are used to manage static or avoid the generation of excess charges. These could include:

• Air showers
• Ionizing blowers
• Sticky mats to collect contaminants
• ESD safe furniture such as chairs and workstations
• ESD garments, gloves, and footwear 
• ESD monitoring equipment

Static control is also important for cleanrooms using fine electronics and sensitive or flammable substances. In the medical industry the production of medical devices might be the application most threatened by static electricity. With intentional cleanroom design and static control cleanroom supplies, you can protect your products and people, encourage efficient operation, and avoid the potential problems of escalated costs or failed products. 

Think you need static control in your medical cleanroom, but not sure where to start? Angstrom Technology can design and build cleanrooms to your specifications using conductive flooring, ESD materials, static control equipment, and more. We have solutions to avoid static buildup and protect your work and employees. Get in touch with our team to learn more.