What are the different clean-room classifications?

Updated on July 8, 2020

Clean-rooms are facilities that are primarily used in scientific research projects, manufacturing, or in highly-specialized industrial production. These rooms are generally designed to offer an environment with an extremely low level of particles like dust, vaporized droplets, aerosol pollutants, and other airborne microorganisms. Clean room solutions are mainly used during the manufacture of pharmaceuticals, medical devices, optics, military items, integrated circuits, and different types of displays e.g. micro-LED.

An overview of clean-rooms

Clean-rooms are a requirement in production processes where very small particles can largely affect the outcome. These rooms come in a variety of sizes and complexity. The cleanliness levels are quantified by the number of particles per cubic meter at a specified particle size and predetermined pressure.

Apart from the regulation of particulate contamination, other parameters such as humidity, temperature, and pressure are also controlled.

The main item that is used is the HEPA (High-Efficiency Particulate Air) filter that traps all particles that are larger than 0.3 microns before delivering it to a clean-room. ULPA (Ultra Low Particulate Air) filters are used if stringent cleanliness is required.

Training and clothing

People who work in clean-rooms go through thorough training in contamination control. They can only get in and out of the rooms via airlocks, air showers, or gowning rooms.

The personnel is also required to put on specially designed clothes to trap any contaminant released by their bodies. Clean-room clothing ranges from hairnets, lab coats, aprons, beard covers, coveralls, face masks, hoods, gowns, bouffant caps, boots, gloves, and finger cots, to bunny suits with self-contained breathing apparatus. The type of garments worn reflects the clean-room specifications.

Clean-room Standards 

There are two main clean-room classification standards

  • FS 209E  
  • ISO 14644-1

Another standard that is used in the UK is the British Standard 5295.

Larger numbers like “class 100” refer to FED_STD-209E which allows interpolation so it’s possible to have high numbers like “class 2000”. On the other hand, smaller numbers like “ISO class 5” refer to ISO 14644-1 standards and they specify the decimal logarithm of the number of particles 0.1 microns or larger per cubic meter of air.

Both classification standards assume log-log relationships between particle size and particle concentration. So, at no point can there be a zero-particle concentration. The ISO 14644-1 is more accepted and used because it adds more classes and, therefore, accommodates major areas that were left out.

Understanding clean-room specifications

Different labs need to implement clean-rooms for assured purity of the research subjects. Once you understand the important role, they play in impacting your results in the lab, you can choose the right clean-room classification that offers the best practices.

The classifications depend on the number and size of the particles per volume of air. There are different levels of clean-room classification based on how clean the air is. Generally, the lower the ratings on the ISO scale, the cleaner the room. Class 1 is the cleanest going up to class 9 which is the “dirtiest”. Here are a few of the classes:

ISO class 1

This class is the cleanest and is mostly applied by life science or nanotechnology industries requiring ultra-fine particulate processes.

The ideal air changes per hour for this class are 500-750. 

80-100% of the ceiling should be covered.

ISO class 2

The ideal air changes per hour for this class are 500-700.

80-100% of the ceiling should be covered.

ISO class 3

The ideal air changes per hour for this class are 400-700.

60-100% of the ceiling should be covered.

ISO class 4

The ideal air changes per hour for this class are 400-700.

50-90% of the ceiling should be covered.

ISO class 5

The ideal air changes per hour for this class are 2400-600.

35-70% of the ceiling should be covered.


The clean-room classification matters a lot on how the room will be used. It also dictates how the room works. For example, positive air pressure is used to keep the air clean and free of particles. On the other hand, negative air pressure is used in industries that deal with infectious diseases or hazardous substances.

The Editorial Team at Healthcare Business Today is made up of skilled healthcare writers and experts, led by our managing editor, Daniel Casciato, who has over 25 years of experience in healthcare writing. Since 1998, we have produced compelling and informative content for numerous publications, establishing ourselves as a trusted resource for health and wellness information. We offer readers access to fresh health, medicine, science, and technology developments and the latest in patient news, emphasizing how these developments affect our lives.

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