Clean rooms are, essentially, just what they sound like. They are rooms with a low level of pollutants. These pollutants are not necessarily what is normally considered air pollution, but rather skin particles, dirt, microbes and chemical vapors. A clean room has a controlled amount of all of these.
- Clean rooms are classified by particles per volume. There are numerous standards of classifying clean rooms. By the FED-STD-209E classifications, a class 10 would have 10 particles larger than .5 micrometers per cubic foot. A class 200 would have 200 such particles.
By the ISO 14644-1 classifications, a class 3 clean room would have 10^3 particles of .1 micrometers or greater per cubic meter. A class 5 would have 10^5 such particles.
Ordinary air is generally FED class 1,000,000 or ISO class 9.
- Special airflow, filtering, protective clothing and other regulations help maintain a clean room.
Many common clothing materials are not allowed, particularly those made from natural fibers. Normal pencils and paper are often excluded, partly because they tend to release particles.
- The air entering a clean room is filtered to prevent outside contaminants from entering. Staff pass in and out through airlocks, which prevent unclean air from entering with them. Staff members also sometimes are showered with clean air prior to entering.
Inside the clean room, air is continuously recirculated to remove pollution generated from within (from manufacturing or the staff). Constant airflow from the ceiling is often used to sweep away contaminants, which leave through filters near the floor.
Clean rooms are sometimes kept at a positive pressures so air leaks will not result in external air entering.
- In order to prevent particles from staff from contaminating the air, most clean rooms require some sort of protective clothing. This can include boots, gloves, face masks, hats and coveralls. Boots are perhaps the most critical because of contaminants collected by shoe soles. Clean-room shoes have to balance the need for a smooth sole that doesn't track dirt and a safe amount of traction.
- Clean rooms come in many sizes. Often, entire facilities will be kept as clean rooms for clean manufacturing.
Clean rooms are often found in the manufacturing of biotechnology, semiconductors and other fields working with sensitive materials.
Often, manufacturing companies will have semi-clean rooms. While they won't follow all procedures for fully minimized air pollution, they will utilize some of the practices. In general, the lower the cost of the clean room, the lower the standards of cleanliness.