What is the difference between a BSL-3 and a BSL-4 facility?
The Centers for Disease Control and the National Institutes of Health have delineated the differences between BSL-3 and BSL-4 facilities in their book, Biosafety in Microbiological and Biomedical Laboratories. There are specific containment requirements that protect the researchers and areas external to the laboratory itself. These are referred to as primary and secondary barriers. Primary barriers include different types of biological safety cabinets, engineering controls, equipment design, in addition to special personnel protective equipment, training and required laboratory practices. Secondary barriers focus on facility design and construction and include different requirements regarding separation from public access, decontamination equipment, specialized ventilation systems, controlled access and entry airlocks.
