A clean room is a building that is constructed to provide for a clean environment for various fields of research such as biological or chemical research, and also for the manufacturing of sensitive components. These purposes often involve environmentally sensitive processes that require an uncontaminated environment. These processes are conducted with procedures that are intended to prevent the contamination of the environment with foreign matter like airborne particles and bacteria; these procedures range from a strict employee dress code, rigorous washing, environmentally isolated lockers and chambers, air showers, and thorough cleaning techniques. The design of the clean room itself incorporates HEPA and ULPA filters to facilitate an air flow through the facility that keeps out contaminants, generally with a positive pressure flow to push contaminants out, or a negative pressure system that keeps everything in, depending on the design objectives.

An example of scientific research that would require a clean room would be when scientists grow cultures that would be ruined if bacteria were to contaminate them. In manufacturing, there are many components that require a clean, uncontaminated environment to be made in, such as microprocessors which could be inhibited with the slightest trace of a foreign particle such as dust or dirt. Generally, employees who work in clean rooms are required to follow specific guidelines for keeping out external contaminants. They will often wear protective clothing with hood coverings, gloves, and masks. They will also pass through air showers to get rid of any particles from the outside before stepping into the clean room environment.

Clean rooms come in several forms, depending on the requirements of the facility. Some clean rooms are hard-walled facilities that are permanent, and then some are flexible soft-walled facilities which can be easily transported, such as for medical emergencies. Some facilities are modular in construction, and can be broken down and moved or kept permanent, depending on preferences.

Clean rooms follow a grading scale that measures the amount of allowable contaminant particles in the air. The ISO system starts at ISO 1, which allows 10 or fewer particles per every 0.5 micrometer cubic area. The allowable particles increase by a factor of 10 with every increase in the ISO rank. Another grading scale that is used is the US federal standard which is numbered 1, 10, 100, 10,000, and so on. Class 1 rooms have 1 particle for every 0.5 micrometer of cubic space, and so on, the Class numbers resembling the maximum amount of particles allowed in 0.5 cubic micrometers.

As for the filtration systems, clean rooms often use HEPA filters and ULPA filters. These filters can remove up to 99.9 percent of the particulates in the air using various air flow systems. There are laminar air flow filters which employ unidirectional airflows; this means that air flows in a straight downward motion, cleaning any particulates. There is also a non-unidirectional airflow type which creates turbulent air conditions which can separate air particles from the air. Some clean rooms employ a positive pressure to keep particles out, and then some employ negative pressure to keep contaminants in. It all depends on what needs to be done in the workspace.

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