Laboratories which house microorganisms for research are similarly categorized, according to design. Containment laboratories are assigned a “biosafety level” (BSL), ranging from 1-4, with BSL-1 laboratories designed with the lowest level of containment. Unlike risk group classifications which are specific to microorganisms affecting humans, laboratory containment levels are used with any type of microorganism regardless of whether it is a human, animal, or plant pathogen. The containment level progressively increases with increasing risks that the organism presents to humans and the environment and considering the type of work to be conducted with the organism.
Microorganisms that present little to no risk to humans or the environment are generally conducted in biosafety level one containment facilities, with consideration given to the laboratory techniques to be conducted. Microorganisms that present grave risk to human health or the environment are worked with in biosafety level 3 or 4 facilities. These organisms are often lethal to a susceptible host and are easily transmitted between members of the host population.
Notice that each containment level builds from the next lower containment. Detailed BSL-1 laboratory practices are discussed later. Note: Organism “Risk Group” and laboratory “Biosafety Level” are not synonymous. It is not accurate to refer to an organism as a “BSL-1 organism.” However, the two concepts do compliment each other. Risk groups correlate to Biosafety Levels, but they are not always equivalent. If a PI has a question regarding microorganism risk group or appropriate biosafety level, please refer them to the BSO.