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What Are Biosafety Levels?

When scientists study microorganisms they are required to work in laboratories designed to protect the scientists from exposure to the microorganism and prevent microorganisms from entering the environment. Depending on the microorganism being studied the scientists work in labs classified under one of four Biosafety Levels (BSL 1-4).

Each Biosafety Levels defines proper laboratory techniques, safety equipment, and laboratory design features required, depending on the route of exposure (by air, by contact, ingestion or fluid transfer) and the health risks a microorganism presents to humans and animals. Each Biosafety Level builds on the requirements of the level below (i.e. BSL-3 must follow all the BSL-2 requirements plus the added requirements for BSL-3). It is important to note that only work at biosafety levels 2 and 3 will occur in the UTHSC RBL. UTHSC cannot perform work at BSL-4 in any of its facilities.

  • BSL-1 is suitable for work involving well-characterized agents not known to consistently cause disease in immunocompetent adult humans, and present minimal potential hazard to laboratory personnel and the environment. BSL-1 laboratories are not necessarily separated from the general traffic patterns in the building. Work is typically conducted on open bench tops using standard microbiological practices. Special containment equipment or facility design is not required, but may be used as determined by appropriate risk assessment. Laboratory personnel must have specific training in the procedures conducted in the laboratory and must be supervised by a scientist with training in microbiology or a related science.
  • BSL-2 builds upon BSL-1. BSL-2 is suitable for work involving agents that pose moderate hazards to personnel and the environment. It differs from BSL-1 in that: 1) laboratory personnel have specific training in handling pathogenic agents and are supervised by scientists competent in handling infectious agents and associated procedures; 2) access to the laboratory is restricted when work is being conducted; and 3) all procedures in which infectious aerosols or splashes may be created are conducted in Biosafety Cabinets (BSC) or other physical containment equipment.
  • BSL-3 is required for work involving indigenous or exotic agents that are transmitted through the air and may cause serious or potentially lethal disease. Laboratory personnel must receive specific training in handling pathogenic and potentially lethal agents, and must be supervised by scientists competent in handling infectious agents and associated procedures. All procedures involving the manipulation of infectious materials must be conducted within Biosafety Cabinets (BSCs), other physical containment devices, or by personnel wearing appropriate personal protective equipment. A BSL-3 laboratory has special engineering and design features that prevent the release of microorganisms to the environment.
  • BSL-4 labs is required for work with dangerous and exotic agents that pose a high individual risk of life-threatening disease, aerosol transmission or unknown risk of transmission. Laboratory staff must have specific and thorough training in handling extremely hazardous infectious agents. Access to the laboratory is controlled by the laboratory supervisor. All handling of agents must be performed in a gas tight Class III Biosafety Cabinet or by personnel wearing a positive pressure protective suit. BSL-4 Laboratories have special engineering and design features to prevent microorganisms from being released into the environment.

For more information, see this Biosafety in Microbiological and Biomedical Laboratories publication prepared by the National Institutes of Health and Centers for Disease Control and Prevention. Section IV provides more detailed information about laboratory biosafety criteria.

Last Published: Sep 30, 2016