SAFETY CABINETS FOR PROTECTED WORK IN LABORATORIES AND CLEAN ROOMS

In class I sterile chambers, the air is extracted from the interior of the safety cabinet through a particulate filter. This prevents the escape of airborne organisms, spores or aerosols.

Part of the extracted air is returned to the laboratory area along the front of the workbench. For this purpose, a powerful ventilation system is installed above the area, which prevents draughts in the laboratory room and ensures efficient air circulation.

Class I safety workbenches are designed to protect laboratory personnel. The air in the workbench working area is fed from the room air and is not pre-filtered. 

Class II safety cabinets have two or three filters (mostly HEPA standard). The fresh air drawn in is cleaned before it comes into contact with the work material, which prevents potential contamination.

Part of the filtered exhaust air blows downwards in a uniform flow as an "air curtain" along the partially opened front window and is fed back to the filter together with the room air drawn in. The flowing barrier minimises the risk of particles from inside the safety cabinet entering the laboratory environment through the front window.

Class III safety cabinets (also called glove boxes) are hermetically sealed and therefore meet the highest safety requirements for laboratory personnel, working materials and the environment. They have built-in gloves and air locks through which tools and working materials are brought in. Both the supply air and the extract air are passed through a highly efficient particle filter. This maintains a negative pressure inside so that no potentially contaminated room air escapes in the event of a leak.

Class II A1 cabinets are suitable for handling products with low or medium biological risk and should not be used for toxic or volatile products.

In Class II A1 safety cabinets, 30% of the total volume is fed into the cabinet as an air curtain via the front sash opening and 70% is circulated as recirculation air from the cabinet via a HEPA. 30% of the total volume is released back into the room via a corresponding filter stage.

Class II A2 cabinets are suitable for applications involving small amounts of radioisotopes or toxic volatiles.

The safety cabinets of Class II A2 correspond to Class II A1 with the difference that 30% of the air is discharged into the open air via an exhaust air system. 

Class II B2 cabinets are designed for use with harmful chemicals, radioisotopes and volatile substances that are toxic even in small quantities.

Here, 70% of the air is fed into the cabinet via a HEPA filter and 30% as an air curtain via the front sash opening. In the process, 100% of the air is led out into the open via an exhaust air system equipped with appropriate filters.