Making Sense of Biological Safety Levels

Biological safety Levels (BSLs) are prescribed by the CDC (Centers for Disease Control and Prevention) to inhibit contamination of a work environment and ensure worker safety by outlining operating procedures and atmospheric controls. If you’ve read the BSL guidance document, you may have found the infection-rate distinctions and cabinet classes hard to conceptualize. Here, we summarize section IV of the Biosafety in Microbiological and Biomedical Laboratories, 5th Edition.


There are four levels of infectious-agent exposure, each designated to abide by a specific set of control designs and protocol. To determine the safety control level, laboratories must consider several factors, including disease transmission and severity, infection potential, microbe or agent origin, and type of work.  See “Biosafety Levels” below for a description of each level.

How do BSLs differ from standardized

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