Cleanroom performance requirements are delineated at three levels of condition for testing and characterisation of performance.
As built: This refers to an empty cleanroom with the filter system running. There is no equipment or workers present in the room. The cleanroom has never been used and is at its cleanest in this state.
At rest: Once equipment and products are added to the cleanroom, it is then referred to as ‘at rest’. Humans have entered the room, but it hasn’t been tested. The room is not as clean as ‘at built’ and may be rated ISO 6.
In operation: Once the cleanroom has been tested for performance requirement, benchmarked and documented, the cleanroom rises to ‘at operational’. Now, the cleanroom is used for the purpose it was created, with human traffic and equipment present within. Humans and processes contaminate the cleanroom environment, so this the dirtiest time for a cleanroom. Corrective steps will be taken if contamination in the operational state is not in compliance with ISO Class 8 requirements.
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