Class 3 safety cabinets in the genetic engineering facility
Dr. Christian Klein
Class 3 safety cabinets are not explicitly required at any genetic engineering safety level – but they are useful.
In the newsletter 03/2023 and 04/2023 The functionality of Class 1 and Class 2 microbial safety cabinets (MSW) was presented. Class 1 cabinets protect the people conducting experiments, but not the experimental material. Class 2 cabinets, on the other hand, offer combined personal and product protection, but still have a direct connection between the laboratory and experimental areas via the access gap. When carrying out work that may generate aerosols, it must be ensured according to the GenTSV that these do not enter the work area (GenTSV Annex 2, IIa). This is ensured in MSW by filtering the process exhaust air using HEPA (high-efficiency particulate absorbing) filters. Therefore, both Class 1 and Class 2 MSW in S1 and S2 systems are suitable for protecting people conducting experiments during aerosol-intensive work. However, the GenTSV does not specify when the use of Class 3 MSW is advisable.
Compared to Class 1 and 2 MSW, Class 3 MSW offers enhanced personal protection because there is no direct opening between the work area and the laboratory. Essentially, it is a closed experimental space with negative pressure. Handling within the workbench is made possible using aerosol-tight, permanently installed gloves guided into the workbench or using manipulators. Experimental material can be introduced via a material lock. The supply air is kept germ-free by a HEPA filter, and the exhaust air by two HEPA filters connected in series. However, the GenTSV does not specify the use of Class 3 MSW.
When working with organisms hazardous to health, i.e., from safety level S2 onwards, the increased structural and technical safety measures relate almost exclusively to measures suitable for preventing an unintentional GMO release from the subsequently tighter containment of the S3 and S4 facilities. Personal protection within the S3 facility would, of course, be improved by the structural classifications of Class 3 MSW, but is subject to an individual risk assessment.
