Biosafety Levels

In the research and clinical treatment fields Biosafety addresses the safe handling and containment of infectious microorganisms and hazardous biological materials. Two important factors in biosafety are containment and risk assessment. The fundamentals of containment include practices for working with microbiological materials, safety equipment, and facility features that protect laboratory workers, the environment, and the public.

The goal is to stop or reduce exposure to infectious microorganisms that are handled and stored in the laboratory.

The US Centers for Disease Control and Prevention defines four safety levels for facilities that handle potentially hazardous microbes: Biosafety Level 1 (BSL 1), BSL 2, BSL 3 and BSL 4. The specifications for each level are combinations of laboratory practices and techniques, presence of safety equipment, and architectural features of the buildings. When assigning levels to facilities, managers and regulators take into account planned operations and the documented and suspected routes of transmission of the infectious agents.

BSL-1 calls for a basic level of containment that relies on standard microbiological practices with no special primary or secondary barriers recommended, other than a sink for hand washing. BSL-2 is the most common level in clinical, diagnostic, and other laboratories that work with the broad spectrum of indigenous moderate-risk agents that are present in the community and associated with most transmittable human disease. The primary hazards to personnel working with these agents include accidental percutaneous or mucous membrane exposure and ingestion of infectious materials. Sharps are also a hazard to workers, both a risk for laceration injury and for allowing infection to enter the bod. Hand washing sinks and waste decontamination rooms or areas, must be available to reduce the risk of environmental contamination.

BSL-3 deals with practices, safety equipment, and facility design and construction for clinical, diagnostic, teaching, research, or production facilities in which work is done with indigenous or exotic agents with a potential for respiratory transmission, and which may cause serious and potentially lethal infection.

BSL 4 deals with practices, safety equipment, and facility design and construction as applicable for work with dangerous and exotic agents that pose a high individual risk of life-threatening disease, which may be transmitted via the aerosol route and for which there is no vaccine or therapy. Labs that deal with viruses such as Marburg or Congo-Crimean hemorrhagic fever are BSL-4.


The term containment refers to methods for safely managing infectious materials in the laboratory environment where they are being handled or maintained. The purpose of containment is to reduce or eliminate exposure of laboratory workers, other persons, and the outside environment to potentially hazardous agents. Laboratory personnel training, safety practices, and techniques must be supplemented by facility design and engineering features, as well as safety equipment. Containment can be primary or secondary.

Primary containment

The protection of personnel and the immediate laboratory environment from exposure to infectious agents is provided by responsible microbiological technique and the use of safety equipment. Research facilities sometimes vaccinate their personnel for an increased level of protection.

Secondary containment

Secondary containment are measures to protect the environment outside the laboratory from exposure to infectious materials. Most secondary containment plans employ a combination of facility design and operational practices. The three elements of containment are laboratory practice and techniques, safety equipment, and building and campus architecture. When developing a secondary containment plan, engineers employ a risk assessment of the planned activities and pathogens or organisms.