"specific combinations of work practices, safety equipment, and facilities to minimize exposure of workers to infectious agents; these range from level 1 for agents not usually causing human disease to level 4 for agents posing a high risk of life-threatening disease, such as the Ebola virus"
Combinations of laboratory practices and techniques, safety equipment, and laboratory facilities appropriate for the operations performed and are based on the potential hazards imposed by the agents used and for the laboratory function and activity. Biosafety Level 1 provides the least stringent containment conditions and Biosafety Level 4 the most stringent.
Four biosafety levels (BSL 1, 2, 3, or 4), consist of combinations of laboratory practices and techniques, safety equipment and laboratory facilities. Each combination is specifically appropriate for the operations performed, the documented or suspected routes of transmission of the infectious agents and for the laboratory function or activity.
the level of safety from exposure to infectious agents; depends on work practices and safety equipment and facilities
One of four combinations of laboratory practices and techniques, safety equipment, and laboratory facilities recommended by the Centers for Disease Control and the National Institutes of Health in "Biosafety in Microbiological and Biomedical Laboratories", as being appropriate for minimizing the risk of infectious disease when microorganisms are worked with. The National Institutes of Health's "Guidelines for Research Involving Recombinant DNA Molecules" also makes use of this classification system in its requirements for safety practices regarding laboratory activities involving organisms that contain recombinant DNA.
The U.S. Centers for Disease Control and Prevention (CDC) specifies four levels of biocontainment precautions for biological agents, Biosafety Levels 1 through 4.