TABLE 1-4.

Biosafety Levels Set for Diagnosis of Laboratory Practices

Level	Risk	Examples	Example Precautions
BSL 1	Minimal potential hazard to human health and the environment	Canine adenovirus-1 Nonpathogenic Escherichia coli	Gloves, facial protection. Standard microbiologic practices using bench-top techniques. Routine decontamination practices (hand washing, routine bench disinfection, autoclaving of infectious waste).
BSL 2	Moderate potential hazard to human health and the environment. Organisms cause mild disease or are difficult to contract as laboratory aerosols.	Most veterinary viruses, including influenza viruses	Access to the laboratory restricted when work is taking place; extreme precautions with sharp contaminated materials; use of appropriate biosafety cabinets when generation of aerosols possible. No requirement for directional airflow into the laboratory.
BSL 3	Dangerous agents that can be transmitted by aerosol within the laboratory but for which effective vaccines or treatments exist.	West Nile virus Equine encephalitis viruses Rickettsia rickettsii Coxiella burnetii Mycobacterium tuberculosis	Laboratory is located away from high-traffic areas. Restricted laboratory access when work in progress; double door entry, ventilation providing airflow into the room, exhaust air not recirculated; special practices and protective clothing for BSL 3, including biosafety cabinet use; special floor and ceiling materials specified.
BSL 4	Dangerous and exotic agents that pose a high risk of aerosol-transmitted laboratory infections, or which produce severe or fatal disease in humans	Ebola virus Marburg virus Smallpox	Hazmat suit and self-contained oxygen system, entrance containing multiple showers, a vacuum room, an ultraviolet light room, and multiple airlocked doors. Strict control of laboratory access to authorized personnel.