Basics of the Not-so-Basic Clean Room

A clean room is a space where environmental pollutants are controlled to a specific level. These rooms are commonly utilized in manufacturing, scientific research, and medical applications when even the tiniest of contaminates will compromise a project. Contaminants include things like dust, airborne microbes, aerosol particles and chemical vapors. They can come from facilities, people, tools, fluids, and products. Even cosmetics, including cologne, hairspray, and fingernail polish, are banned from a clean room. While it is impossible to completely eliminate all contaminants, the levels of acceptable contaminates vary by clean room.

Definition of Classes

The controlled level of contamination is designated by the number of allowed particles per cubic meter at a specified particle size. A discrete-particle-counting, light-scattering instrument measures the particles in the air. There are different standards used to denote the accepted level of contaminates. The Federal Standard 209 E is commonly used, so to keep it simple, we will use this standard to exemplify the class levels.

A typical office building contains between 500,000 and 1,000,000 particles that are 0.5 microns or larger per cubic foot of air. A Class 100 clean room doesn’t allow more than 100 particles (0.5 microns or larger) in a cubic foot of air. A Class 1000 would limit it to 1000, and this pattern is consistent throughout the classes. For the Federal Standard 209 E, the classes are 1, 10, 100, 10,000, and 100,000.

Each class also outlines the number of allowed particles per cubic foot that are 0.1, 0.2, and 0.3 microns or larger in size. A Class 100 allows 3500 at 0.1, 750 at 0.2, and 300 at 0.3. The corresponding standards for a Class 10 would be 350, 75, and 30 (and 10 at 0.5).

Sources of Contamination

Contaminates can get into a clean room in three ways: in the air, on a person, or on incoming equipment.

Air: The flow of air itself is controlled to move with the least amount of restriction possible. The more the air is restricted, the more turbulence it can create, and turbulence causes particles to move. The architecture of the clean room will be designed for the best airflow.

Additionally, filters are an important part of the air control process. High Efficiency Particulate Air Filters (HEPA) are crucial to the clean room environment. Other filters are sometimes used as well, to remove particles from gases and liquids.

People: Depending on the Class, clean rooms may have ante-rooms that people use to enter and exit the room. In most cases, specific garments are required, and they usually include face masks, gloves, hoods, coveralls, and/or boots. The contaminates people carry can come in through the products they use as well as their skin flakes, hair, skin oil, spittle, and clothing debris like lint.

Equipment: This is a very broad category. It includes everything from tools and writing utensils to paint and debris (i.e.: from air conditioners.) The room has to be built and cleaned with compatible materials. These materials, however, are still prone to contaminating the environment.

Some Protocols

Selecting the proper materials, air filtration, and garments to use in the room is only half of the process to keep the room up to its standards. People are one of the greatest sources of contamination in a clean room. A person who is simply standing still will produce 100,000 particles/minute that are 0.3 microns or larger. Horseplay will produce 100,000,000 particles/minute. Human behavior and attitude are major factors in contamination.

Other protocols have to do with cleaning. Every task and item used is scrutinized. Changing mats, mopping, vacuuming, removing trash, and wiping surfaces all must be done a certain number of times a shift and done in a specific manner.


Thanks to clean rooms, invented by Willis Whitfield, we are able to enjoy the greatest advancements in technology, science, and medicine. Designing and working in a clean room takes extreme care, caution, and discipline. It is because of the people who follow strict regulations and standards that inventions like the Hubble Telescope and vaccines are a part of our lives today.


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