Air pressure in Critical environments and cleanrooms
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For many industries, a cleanroom plays a vital role in the manufacturing process to achieve the desired output.  A cleanroom is an enclosed critical environment where air contaminants are eliminated.  For an environment to be considered as a clean room, it has to pass a standard. 

The Cleanroom Standards

The International Standards Organization (ISO) created a working committee and groups.  They are tasked to develop a new set of criteria for the cleanroom standards. And in November 2001, ISO 14644-1 and 14644-2 were published. But before this ISO cleanroom standard was developed, the US agencies approved and adopted the Federal Standards 209E (FS209E)

ISO 14644-1 and 14644-2 measured the number of air particulates in specific sizes that exist in cubic per metric. Whereas the FS209E measures the amount of particulate in specific sizes that exist in cubic per foot. The FS209E consists of six classes in the nominal class of 1, 10, 100, and 100,000. Class 1 is the cleanest, and Class 100,000 is the dirtiest. On the other hand, the ISO uses the Class Levels such as ISO 1, 2, 3, etc. Comparing the two standards, the counterpart of FS209E class 1 is ISO 3 while there are still ISO 1 and 2, which are more sterile in the category. 

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The Critical Environments

Strict adherence to the cleanroom standard is necessary for a critical environment.  It protects the internal sample or materials and the workers involved in the process. There are many things to be considered in the construction of a critical environment. FDA and USDA-approved construction materials have emphasized the need to have a smooth surface that is unable to generate air particulates. Interaction technology that passes through facilities is also essential. It will limit the air surface’s contaminants and maintain and clean procedures.

In a critical environment like cleanrooms and server rooms, an HVAC system is designed to have proper airflow and enough volume of air. It also promotes precise air temperature and humidity requirements. The HVAC system could use either or a combination of HEPA filter and ULPA filter to achieve an almost 100% efficiency rating in trapping and eliminating air particulates.

The internal air pressure is one of the most vital components of a cleanroom. High-pressure air has a greater mass than low-pressure air to flow into the lesser dense environment. The specific combination of ascending and descending pressure differentials between adjacent areas eliminates the inflow of airborne particulates.  It can also prevent hazardous materials from escaping the enclosed space.

The Positive Pressure

This means that the air pressure inside your critical environment such as cleanrooms is greater than the pressure outside of it. A positive pressure room is produced 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 critical environment. 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.

The Negative Pressure

In a negative air pressure cleanroom, the air pressure in the room is lower than the pressure outside of the critical environment. 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, the 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 right-side-up, water flows into the cup, because it has lower pressure than the water. The negative pressure cleanroom is like the empty cup here.

How is Pressure Differential Measured?

Professionals often employ digital gauges or meters to facilitate the identification of current pressure levels inside and outside of cleanrooms. The devices are designed to automatically calculate and output the difference between two pressure points in the cleanroom, eliminating the need for operators to manually monitor separate gauges and calculate the difference between the results. More advanced measuring instruments may offer additional capabilities for monitoring temperature, humidity, and other cleanroom parameters.

The Importance of  Pressure Differential

Differential pressure refers to the difference in air pressure from one location to another within a system. In cleanrooms, maintaining the right amount of differential pressure—either positive or negative—is essential to preventing contamination. A combination of positive and negative pressure with the appropriate temperature, humidity, and airflow level, ensures cleanroom designs work as intended. As such, it is essential to carefully measure and monitor pressure inside and outside of the cleanroom to confirm the differential remains within the acceptable range.

How are these Pressure-Controlled Areas Used?

Many industries use pressure-controlled critical environments.  Here are some of these:

  • Electronics Industry

The manufacturing of microchips, conductors, and circuits needs a sterile environment.  It must use positive pressure to avoid compromising the product. Manufacturing highly sensitive electronics parts such as circuit boards, microprocessors, satellite assembly require a dust-free and humid-free environment.  Otherwise, it will result in damaged and ineffective electronics products. 

  • Pharmaceuticals

According to World Health Organization, pharmaceutical companies must maintain 10 to 15 pascals of pressure differential to ensure positive pressure. This will keep the airflow from aseptic to non-aseptic. This pharmaceutical process is critical in preventing contamination through powder form, bacterial, and even microbial growth. There are positive airlocks that are used to prevent loss of the higher pressure. With the pressure difference, these contaminants will avoid entering the sterile environment.

  • Water Testing

According to the US Environmental Protection Agency, an ISO 5 or Class 100 for FS209E cleanroom with positive air pressure is required to accurately test traces of metals, trace elements, and other contaminants in drinking water, wastewater, and groundwater.

  • Vaccine Research and Production

Today, there are many contagious diseases such as the Ebola Virus and Coronavirus, and other viruses that threaten human health. There are millions of death recorded around the globe because of these viruses. Thus, vaccine production plays a vital role in ensuring health safety. Storing vaccines is so dangerous that any careless and negligent treatment can result in a deadly vaccine. The vaccine production process uses a positive pressure chamber to maintain cleanliness, contamination-free, and safety. Cleanrooms ensure that the viruses in vaccine production are fully contained and restricted from contamination. Similarly, the negative air pressure room ensures the safety of the personnel and the surrounding area.

Pressure Gauges and Monitors

It is important to check the air pressure regularly in a critical environment. A few moments of delay in differential pressure changes can be risky. Just for example in a vaccine production lab, with a sudden change in the pressure, the contained virus might easily escape. Massive contamination from personnel to nearby populations might occur and no one would like another epidemic.

Wireless Tunnel HVAC Monitoring System

AKCP Wireless Air Pressure Differential

Wireless Differential Air Pressure

AKCP Wireless Tunnel™ radio module with differential air pressure. Monitor cabinets for pressure differential to ensure adequate airflow. Air Pressure Differential Sensors can also be utilized in hospitals or clean rooms where positive pressures are maintained inside rooms to keep them clean, or negative pressures to contain contaminants.

Sensor Details
  • 4x AA Batteries
  • External 5VDC or 12VDC power
  • LED indicators for power, status, and RSSI
  • Optional DIN rail or pipe mounting

Established in the USA in 1981, AKCP has over 30 years of experience in monitoring solutions. AKCP prides itself on over 200,000 installations in professional sensor solutions. It boasts itself on the integrity of product quality. The company implemented outstanding support to all customers. With the winning combination of technical excellence and total support, AKCP remains the leader in the industry.

Visit www.akcp.com and get to know more about the sensors and monitoring solutions for commercial and residential applicable products.

References Links:

https://www.setra.com/critical-environments/cleanrooms

https://www.terrauniversal.com/blog/under-pressure-in-critical-environments

https://www.news-medical.net/health/What-are-Negative-Pressure-Rooms.aspx#:~:text=They%20are%20called%20negative%20pressure,outside%20into%20non%2Dcontaminated%20areas

https://cleanroomtechnology.com/news/article_page/Differential_pressure_explained_simply/135889

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