AS 2252.5:2017 Controlled environments
5.3.1 Work zone
The work zone is the internal space between the viewing window and air intake grille, the work floor and the protective guard below the supply HEPA filter.
5.3.2 Viewing window
The front of the cabinet shall include a viewing window extending the full width of the work zone to form a positive seal with the body of the cabinet in the working position. Materials selected for the viewing window shall be shatterproof and tested and proven to remain transparent and resistant to any change that would prevent clear visibility. It shall be capable of being completely cleaned without removal.
The window should be vertically aligned with the front boundary of the unidirectional airflow outlet. Where a hinged window is used, a means shall be provided to secure the window in the closed position. Where a sliding window is used, mcans shall be provided to locate the window in the normal operating position.
To facilitate cleaning and placement of equipment within the cabinet, means should be provided for holding the viewing window in the open position. An audible or prominently visible alarm, which is activated when the window is other than in the fully-open or closed position, shall be ftted.
5.3.3 Air barrier and containment of hazardous material within the CDSC
The design of the unit shall ensure that the integrity of the work zone is maintained so as to prevent entrainment of air from outside the unit.
An air barrier shall be created across the full width of the access opening by the induction of room air downwards through the air intake grille into the sump. This provides the primary barrier for the operator, product and surrounding environment. The combination of the air drawn into the cabinet from the outside and the air from the work zone shall pass beneath the work floor through the sump HEPA filter to the lower plenum, then via the return air plenum to the negative pressure plenum. A portion of the air at this point is exhausted out of the cabinet, to a volume that is equal to the air drawn in.
To enhance containment of hazardous materials within the cabinet, all potentially contaminated zones shall be under a negative air pressure relative to their immediate surroundings.