Primary Containment and User Comfort
In the 1950s when Class III BSC became widely used in the nuclear and defense departments the primary focus for design was on absolute containment, with little attention given to ergonomic/user comfort. Class II BSC became popular in the 1970s and provided the user with an alternate means of primary containment. While Class II BSC do not provide the same level of user and environmental protection, based on a risk assessment they do have a rightful and very useful place in the biocontainment laboratory. In recent years with increasing work conducted at BSL-4 and the advent of samples containing mixed hazards or biological powders, there has been a significant resurgence in the use of Class III BSC in research, public health labs and with emergency responders. It was time for the Class III BSC to be improved upon and redesigned for diverse missions.

What has changed for Class III Biosafety Cabinets?
Lessons learned from Class II BSC & Biocontainment Lab Design

Lessons have been learned and applied regarding enhancements to ergonomics. Some have been taken from the design of Class II BSC such as use of:

10 degree tilt view panel to allow the user to lean into the screen for comfort and to reduce glare
Adjustable deck height to provide more/user required leg room and accommodate work in a seated position
Control panels that are positioned so they can be observed easily by the operator

Other innovations were developed to increase user range of motion and decrease fatigue, to include:

Extra large, oval shaped gloveports to allow for natural arm positioning and extended reach
A wide rimmed gloveport to enable the user to rest their arms
The use of motion studies to determine the best locations for gloveports and to better size the work area (after all, what is the benefit of Having a 33 inch (0.9 meter) deep BSC if you can not reach the back wall for manipulations or cleaning).

Other improvements were made when considering how containment labs are designed. Class II Biological Safety Cabinets really have not changed much in 30 years and still have right angles where the walls, deck, back panel and ceiling meet. This can pose a challenge when wiping down surfaces during decontamination. Per the CDC/NIH BMBL, WHO and Canadian Biosafety Guidelines, modern labs are constructed with coved or radiused joints to facilitate cleaning and prevent material from being trapped in 90 degree joints. Rounded joints were easily incorporated into new Class III BSC designs. Again, as in lab design, pass through boxes have been developed for BSC with interlocks and alarms to facilitate material transfer and prevent a accidental breach of containment.

Interestingly the flow of design information is now going from Class III BSC to applications in the laboratory...namely the use of Rapid Transfer Port embeds into laboratory walls. These mate with mobile Class III Biological Safety Cabinets to facilitate the transfer of animals from the BSC to the holding room.

Prospective improvements have few limits as most Class III BSC are custom designed...the next advances will likely combine user requirements and ingenuity and manufacturer problem solving and design expertise.

References
Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th Edition (Download PDF)
Public Health Agency of Canada's Laboratory Biosafety Guidelines (Download PDF)
World Health Organization Biosafety Manual (Download PDF)