Description
Most regulatory documents that establish requirements for cleanrooms in various industries, be they clean rooms in medical institutions, pharmaceutical plants, laboratories, or in the manufacture of medical products, require reliable separation of clean rooms (clean zones) of different classes, so that so that pollution from the “dirtier” zone does not affect the processes occurring in a cleaner room.
Approaches to the separation of clean rooms with different classes of cleanliness
Depending on the purpose of clean rooms and the operations performed in them, one of three approaches can be applied to the separation of clean zones of different classes:
separation of clean zones according to the principle of pressure drop between adjacent rooms by providing a higher pressure in a cleaner room
separation of clean areas due to the displacing air flow directed from a cleaner room to a dirtier one
separation of clean zones by the barrier method using an impermeable barrier that completely eliminates the flow of air and pollution from one room to another.
The first approach assumes that adjacent rooms are isolated from each other using doors or windows that can periodically open and close, and the system of supply and exhaust ventilation of clean rooms is regulated and equipped with automatic equipment capable of detecting the opening and closing of doors and maintain a constant pressure differential between rooms, both at closed doors, and at opened. In a clean room of higher purity class, a positive pressure drop relative to adjacent rooms should be provided.
In case of separation of clean rooms according to the principle of the displacing air flow, the ventilation system should provide a displacing air flow directed from a cleaner room to a less clean one, for example, through the slots under the door or special "windows" in wall partitions, doors, windows. The velocity of the displacing flow must be high enough to prevent the backflow of air.
The latter approach - using an impenetrable barrier - is used in cases when completely incompatible operations are performed in adjacent clean rooms, and air must not be allowed to flow not only from a cleaner room into a “dirty” one, but vice versa.
How to control the separation of clean rooms with a different class of cleanliness
When validating clean rooms (clean zones), it is necessary to make sure that adjacent clean rooms with different cleanliness classes are reliably separated from each other and there is no air flow from the “dirty” zone to the clean one.
The measurement technique depends on which principle of clean room separation is used in each specific case.
In case the adjacent clean rooms are divided according to the principle of pressure drop, in the design and construction of the clean room complex, fittings should be provided for connecting a differential pressure gauge to measure the pressure drop. In the case of applying the clean room separation approach according to the principle of pressure drop, the differential pressure can be continuously monitored using built-in pressure gauges.
If the separation of clean areas is due to the displacing air flow, during the certification, the air flow rate is measured and the direction of its movement through all the openings in the room is estimated.
Measurement results of pressure drop and displacement flow rate
The report on the testing of a clean room includes information on the measured pressure drops and / or speeds of the displacing air flow, conclusions are drawn on the compliance of the room with these indicators.
