Microbiological safety cabinets (MSW) in genetic engineering facilities – Class 1 safety cabinets

During genetic engineering work that generates aerosols, it must be ensured from safety level 2 onwards that these do not enter the work area (GenTSV, Annex 2, A. II. a. No. 6). The core technical measure here is the microbiological safety cabinet (MSW). However, even when working with S1 organisms, e.g., during cloning work in E. coli K12 strains, the use of safety cabinets is recommended to prevent the spread of contamination. The basic principle of all MSW is that a directed airflow is generated within a shielded work area, protecting the experimenting personnel and the room air from aerosol-mediated contamination. In all safety cabinets, the air escaping from the work area is therefore passed through one or more high-efficiency particulate absorbing (HEPA) filters. Particular attention should be paid to the placement of the MSW in the laboratory. This is because air movement in the room, at least in "semi-open" Class 1 and 2 MWs, may interfere with the airflow directed toward the HEPA filter within the workbench. In the event of interference, microorganisms could disrupt the airflow, causing biological agents to escape from the MW. Therefore, MWs should not be placed near doors, windows, walkways, or the inlet and outlet openings of laboratory ventilation systems.

The Class 1 workbench: A Class I safety cabinet (see illustration) is essentially a modified fume hood. However, unlike a conventional chemical fume hood, the process exhaust air is vented through a HEPA filter into the room surrounding the MSW. Persons in the room are thus protected from exposure to biological agents. However, sterile work with biological material cannot be guaranteed under these Class 1 safety cabinets. From an occupational health and safety perspective, a Class I MSW offers very good protection against biological agent exposure; however, any hazardous substances are recirculated into the room air. Class 1 safety cabinets are therefore well suited, among other things, for operating devices underneath them that potentially release biological agent aerosols into the environment. Examples of this would be FACS analyzers or FACS sorters used for experiments with GMOs or risk group 2 biological agents.

Conclusion: Work that can be carried out under non-sterile or semi-sterile conditions but which generates aerosols contaminated with biological agents can be carried out under Class 1 microbiological safety cabinets.