Clean rooms as name indicates are clean environments having specific conditions as required by various manufacturing industries. Clean rooms also includes but not limited to having specified temperature, relative humidity and other conditions in it. Clean rooms are classified into various categories and these classification nomenclatures may differ from institutes and regulatory authorities using it. Like Grade A, Grade B , Grade C, etc other nomenclature include class 100, class 1000 , Class 100000 etc, ISO defines various classified areas using nomenclature like Class ISO 5 , Class ISO 6, Class ISO 7 etc. These areas are commissioned, validated and used. There use depends upon the criticality of the work which is performed within it and also on the stringent requirements for users as specified by regulatory authorities and various standards.

Class 100 area is defined as area where there should not be more than 100 particles of 0.5 micron per cubic foot of air. Class 1000 defined same where there should not be more than 1000 particles and so on respectively. Clean room has HEPA filters to clean the incoming area. HEPA means high efficiency particulate air. As the name suggest, the air has specific velocity with which it travels within the room in laminar way that is in parallel way. Laminar means parallel and in clean rooms specific laminar benches are provided to perform the aseptic work these are known as laminar air flow bench (commonly known as LF benches). These benches has a platform to perform scientific or aseptic work and the same is having clean environment due to presence of HEPA filter in the bench itself. These Laminar benches are divided into two types; they are either horizontal or vertical. Vertical laminar benches are also known as biological safety cabinets.

Biological safety cabinet or laminar air flow benches are kept in area which is also classified area. If the laminar flow bench is class 100, then the background area is class 1000 or class 10,000. Positive pressure is thus maintained in gradient such that with the positive pressure from inside the room, the air is flowing outside into unclassified area. This is also very important requirement to maintain the classified area. The positive pressure is having specified requirements with respect to each other in clean room and has been defined in various manuals depending upon the use by the manufacturer. Clean rooms also have controlled temperature and relative humidity these are required for controlling contamination and for increasing the efficiency of aseptic conditions within the room. Today many industries need more stringent conditions than class 100 area. These are either class 10 or even below it. These areas are specifically used in many nanotechnology and related research.

The validation of such area is very important to ensure that these areas meet all the requirements consistently as specified in various international standards and as required for manufacturing & testing. While performing the validation of these areas, velocity of air of classified area, particulate count of air, filter integrity, viable count limits etc area tested and evaluated for their compliance to the specifications. During area validation, temperature and relative humidity is also assessed for its compliance. Air changes are also evaluated. There are specific requirements for air changes also depending upon the classification of the clean rooms. All the instruments with which these validation is performed are also reviewed for its calibration status, traceability etc.

As microorganisms are present all over the world and almost in every condition including extreme conditions of Antarctica and in hot lakes also. Therefore due to its omnipresence, there is a requirement to perform various operations, tests, productions etc in isolated conditions or clean rooms to avoid contamination. Clean rooms had changed the world of aseptic processes and had brought a revolution in microbiology specifically in the field where aseptic conditions are compulsory.

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