A clean room is an environment, typically used in manufacturing or scientific research that has a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapors. More accurately, a clean room has a controlled level of contamination that is specified by the number of particles per cubic meter at a specified particle size.

Clean rooms can be very large. Entire manufacturing facilities can be contained within a clean room with factory floors covering thousands of square meters. They are used extensively in semiconductor manufacturing, biotechnology, the life sciences and other fields that are very sensitive to environmental contamination.

The air entering a clean room from outside is filtered to exclude dust, and the air inside is constantly re circulated through high efficiency particulate air (HEPA) and/or ultra low particulate air (ULPA) filters to remove internally generated contaminants.

Staff enter and leave through airlocks (sometimes including an air shower stage), and wear protective clothing such as hats, face masks, gloves, boots and cover-all.

Equipment inside the clean room is designed to generate minimal air contamination. Even specialized mops and buckets exist. Clean room furniture is also designed to produce a minimum of particles and to be easy to clean.

Common materials such as paper, pencils, and fabrics made from natural fibers are often excluded; however, alternatives are available. Clean rooms are not sterile (i.e., free of uncontrolled microbes) and more attention is given to airborne particles. Particle levels are usually tested using a particle counter.

Some clean rooms are kept at a positive pressure so that if there are any leaks, air leaks out of the chamber instead of unfiltered air coming in.

Some clean room HVAC systems control the humidity to low levels, such that extra precautions are necessary to prevent electrostatic discharge (ESD) problems. These ESD controls (“ionizers”) are also used in rooms where ESD sensitive products are produced or handled.

Low-level clean rooms may only require special shoes, ones with completely smooth soles that do not track in dust or dirt. However, shoe bottoms must not create slipping hazards. Entering a clean room usually requires wearing a clean room suit.

In cheaper clean rooms, in which the standards of air contamination are less rigorous, the entrance to the clean room may not have an air shower. There is an ante-room, in which the special suits must be put on, but then a person can walk in directly to the room.

Some manufacturing facilities do not use fully classified clean rooms, but use some clean room practices together to maintain their cleanliness requirements.

Read more about clean room standards

What is HVAC/ULPA