We saw this image in the last section on Basic Biosafety, but here we expand on the explanation provided in that section to give you a better understanding of the differences between containment levels. BSL-1 is the least rigorous containment designation and is appropriate for work involving well-characterized agents not known to consistently cause disease in healthy adult humans, and present minimal potential hazard to laboratory personnel and/or the environment.” For example, most work involving cloning of genes, protein expression, PCR, etc. using K-12 strains of Escherichia coli or Saccharomyces cerevisiae are usually conducted at BSL-1.
BSL-2 is a suitable level of containment for work involving agents that pose moderate hazards to personnel and/or the environment. This is the most common containment level for UNL laboratories and is the focus of this training module. Examples of work that is often properly conducted at Biosafety Level 2 include manipulation of human tissues, blood, or cell lines and work with pathogenic strains of E. Coli and Salmonella.
BSL-3 and BSL-4 labs are considered “High Containment” Labs where the room becomes a containment device and a barrier to prevent escape of the organism being studied.
BSL-3 containment is necessary when agents pose serious hazards to personnel and/or the environment. Human pathogens transmitted by the aerosol route are often handled in a BSL-3 laboratory. At BSL-3 there are many sophisticated design features, such as entry through an ante room, all utility penetrations and wall, floor, all ceiling seams are tightly sealed, all exhaust air is directed through a HEPA filter, etc. As examples: (1) Experiments conducted with live Mycobacterium tuberculosis are generally conducted at BSL-3. (2) Experiments with pathogens that if released to the environment could result in economic impacts due to morbidity or mortality or trade implications would likely be conducted at BSL-3. An example is Highly Pathogenic Avian Influenza Virus.Very few experiments are conducted at UNL that require BSL-3 containment.
BSL-4 is reserved for those agents posing severe risk to humans, exposure to which often has lethal consequences, for which there is usually no known treatment or cure, and which have potential for rapid and easy transmission from one susceptible host to another. At this level, the laboratory serves as a containment structure and workers are protected by wearing a positively pressurized suit (to keep the infectious agents out) while working in the lab. There are a relatively small number of these labs in the U.S. and most are operated by the government. UNL does not own/operate any BSL-4 facility. An example of a agent that would generally be handled at BSL-4 containment is Ebola virus.