- Biosafety Level 3 (BSL-3) is a specialized laboratory classification designed for work with indigenous or exotic pathogens that can cause serious or potentially lethal disease through inhalation. Unlike BSL-2 organisms, which pose moderate risks, BSL-3 agents are associated with significant health threats, especially due to their potential for airborne transmission.
- Examples of BSL-3 pathogens include Mycobacterium tuberculosis, Coxiella burnetii, Francisella tularensis, Chlamydia psittaci, and certain arboviruses like West Nile virus and Yellow fever virus. Vaccines or effective treatments may not always be available for these agents, which makes containment critical.
- The facility design of a BSL-3 laboratory is more stringent than BSL-2, with multiple layers of protection. The lab must have controlled access, self-closing and lockable double-door entry, and directional airflow (air flows from “clean” areas into “dirty” areas to prevent pathogens from escaping). All exhaust air must be HEPA-filtered and released outdoors without recirculation. Windows are sealed, and the laboratory is constructed to be easily decontaminated. Decontamination systems such as autoclaves or chemical dunk tanks are required for materials leaving the facility.
- Work practices in a BSL-3 setting are highly regulated. Personnel must undergo specialized training in handling pathogenic and potentially lethal agents, and they must be supervised by scientists experienced in working under high-containment conditions. Laboratory staff wear protective clothing, gloves, and respiratory protection as needed. All manipulations of infectious materials must be conducted in a Class II or Class III Biological Safety Cabinet (BSC) to prevent exposure to aerosols. In many facilities, workers also use powered air-purifying respirators (PAPRs) for added protection.
- Safety protocols emphasize minimizing risks of aerosol generation, spills, and accidental exposures. Access to the facility is restricted to authorized personnel, and staff may be subject to medical surveillance programs, including vaccinations or routine health checks depending on the agents in use. Waste disposal is tightly controlled—infectious materials are sterilized before disposal, and equipment is disinfected after use. Emergency procedures for spills, exposures, or equipment failure are clearly established and regularly practiced.
