Summary of Recommended Biosafety Containment Levels for Infectious Agents​


​​Biosafety Level Decription Practices​ Primary Barriers and Safety Equipment
Facilities (Secondary Barriers)​
​1 BSL1 is suitable for work involving well characterized agents not known to consistently cause disease in immunocompetent adult humans and present minimal potential hazard to laboratory personnel and the environment The laboratory is not separated from the general traffic patterns in the building. Work is typically conducted on open bench tops using standard microbiological practices. Special containment equipment or laboratory design is not required, but may be used if appropriate. Laboratory personnel have specific training in the procedures conducted in the laboratory and are supervised by a scientist with general training in microbiology or a related science.
  • ​Protective coats, gowns, or uniforms are recommended to prevent contamination of personal clothing.
  • Wear protective eyewear when conducting procedures that have the potential to create splashes or microorganisms or other hazardous materials. Persons who wear contact lenses in the laboratory should also wear eye protection.
  • Gloves must be worn to protect hands from exposure to hazardous materials. Glove selection should be based upon the risk assessment. Alternatives to latex gloves should be available.
  • Hands should be washed before leaving the laboratory.
Laboratory bench and sink required.
​2

Biosafety Level 2 builds upon BSL1 and is suitable for working with agents of moderate potential hazard to personnel and the environment.

It differs from BSL1 in that: 1) laboratory personnel have specific training in handling pathogenic agents and are directed or supervised by scientists competent in handling infectious agents and associated procedures, 2) access to the laboratory is limited (restricted) when work is being conducted, and 3) all procedures in which infectious aerosols or splashes may be created are conducted in biological safety cabinets or other physical containment equipment.

  • Biological Safety Cabinets (Class I or II) or other appropriate personal protective or physical containment devices are used whenever:
    • Procedures with a high potential for creating infectious aerosols or splashes are conducted. These include centrifuging, pipetting, grinding, blending, vigorous shaking or mixing, sonic disruption, opening containers of materials whose internal pressure may be different from ambient pressures, intranasal inoculation of animals, and harvesting infected tissues from animals or eggs.
    • High concentration or large volumes of organisms containing recombinant or synthetic nucleic acid molecules or other biohazardous agents are used. Such materials may be centrifuged in the open laboratory if sealed beads or rotor heads or centrifuge safety cups are used and if they are opened only in a biological safety cabinet.

  • Protective laboratory coats, gowns, smocks, or uniforms designated for laboratory use must be worn while working with hazardous materials. Protective clothing must be removed before leaving for non-laboratory areas (e.g., cafeteria, library, and administrative offices. Protective clothing must be disposed of appropriately, or deposited for laundering. Laboratory clothing should not be taken home.

  • Eye and face protection (goggles, mask, face shield or pother splatter guard) is used for anticipated splashes or sprays of infectious or other hazardous materials when the microorganisms or materials must be handled outside of the biological safety cabinet or containment device. Eye and face protection must be disposed of with other contaminated laboratory waste or decontaminated before reuse. Persons who wear contact lenses in the laboratory should also wear eye protection.

  • Gloves should be worn to protect hands from exposure to hazardous materials. Glove selection should be based on an appropriate risk assessment. Alternatives to latex gloves should be available. Gloves must not be worn outside the laboratory. BSL2 laboratory personnel should:
    • Change gloves when contaminated, glove integrity is compromised, or when otherwise necessary. 
    • Remove gloves and wash hands when work with hazardous materials has been completed and before leaving the laboratory.
    • Not was or reuse disposable gloves or used gloves with other contaminated waste. Hand washing protocols must be rigorously followed.

  • Eye, face, and respiratory protection should be used in rooms containing infected animals as determined by the risk assessment.

  • The laboratory is designed so that it can be easily cleaned and decontaminated. Carpets and rugs in laboratories are not permitted.

  • Bench tops are impervious to water and resistant to acids, alkalis, organic solvents, other chemicals, and moderate heat.

  • Laboratory furniture is sturdy and capable of supporting anticipated loads and uses.  Spaces between benches, cabinets, and equipment are accessible for cleaning.

  • Chairs used in the laboratory must be covered with a non-porous material that can be easily cleaned and decontaminated with appropriate disinfectant.

  • Each laboratory contains a sink for hand washing. The sink may be manual, hands-free, or automatically operated. It should be located near the exit door.

  • Laboratory windows that open to the exterior are not recommended. However, if the laboratory has windows that open to the exterior, they are fitted with fly screens.

  • An autoclave for decontaminating laboratory wastes is available.

  • Laboratory doors should be self-closing and have locks in accordance with institutional policies.

  • Biological safety cabinets (BSCs) must be installed so that fluctuations of the room air supply and exhaust do not interfere with proper operations. BSCs should be located away from doors, windows that be opened, heavily traveled laboratory areas, and other possible airflow disruptions.

  • Vacuum pumps should be protected with liquid disinfectant traps.

  • An eyewash station must be readily available.

  • When planning facilities, a mechanical ventilation system that provides inward flow of air without recirculation to spaces outside the laboratory should be considered.

  • HEPA filtered exhaust air from a Class II BSC can be safely re-circulated back into the laboratory if the cabinet is tested and certified at least annually and operated according to manufacturer’s recommendations. BSCs can also be connected to the laboratory exhaust system by either a thimble (canopy) connection or directly exhausted to the outside through a hard connection. Provisions to assure proper safety cabinet performance and air system operation must be verified.

  • A method of decontaminating all laboratory wastes should be available in the facility (e.g., autoclave, chemical disinfection, incineration, or other validated decontamination methods.

​3

Biosafety Level 3 is applicable to clinical, diagnostic, teaching, research, or production facilities in which work is conducted with indigenous or exotic agents which may cause serious or potentially lethal disease as a result of exposure by the inhalation route of exposure.

Laboratory personnel have specific training in handling pathogenic and potentially lethal agents and are supervised by competent scientists who are experienced in handling infectious agents and associated procedures. All procedures involving the manipulation of infectious materials are conducted within biological safety cabinets or other physical containment devices or by personnel wearing appropriate personal protective clothing and devices. The laboratory has special engineering and design features, such as access zones, sealed penetrations, and directional airflow

Biological Safety Cabinets (Class I, II, or III) or other appropriate combinations of personal protective or physical containment devices are used for all activities with organisms containing recombinant or synthetic nucleic acid molecules which pose a threat of aerosol exposure.

  • The laboratory is separated from areas which are open to unrestricted traffic flow within the building. Passage through two sets of doors is the basic requirement for entry into the laboratory from access corridors or other contiguous areas. Physical separation of the high containment laboratory from access corridors or other laboratories or activities may be provided by a double-door clothes change room, airlock, or other access facility which requires passage through two sets of doors before entering the laboratory.

  • The interior surfaces of walls, floors, and ceilings are water resistant so that they can be easily cleaned. Penetrations in these surfaces are sealed or capable of being sealed to facilitate decontaminating the area.

  • Bench tops are impervious to water and resistant to acids, alkalis, organic solvents, and moderate heat.

  • Laboratory furniture is sturdy and spaces between benches, cabinets, and equipment are accessible for cleaning

  • Each laboratory contains a sink for hand washing. The sink is foot, elbow, or automatically opened and is located near the laboratory exit door.

  • Windows in the laboratory are closed and sealed.

  • Access doors to the laboratory or containment module are self-closing.

  • An autoclave for decontaminating laboratory wastes is available preferably within the laboratory.

  • A ducted exhaust air ventilation system is provided.

  • The high efficiency particulate air/HEPA filter exhaust air from Class I or Class II biological safety cabinets is discharged directly to the outside or through the building exhaust.

  • For additional BSL3 requirements pertinent to specific organisms or agents refer to the NIH Guidelines and the BMBL.
​4

Biosafety Level 4 is required for work with dangerous and exotic agents that pose a high individual risk of aerosol-transmitted laboratory infections and life-threatening disease that is frequently fatal, for which there are no vaccines or treatments, or a related agent with unknown risk of transmission. Agents with a close or identical antigenic relationship to agents requiring BSL4 containment must be handled at this level until sufficient data are obtained either to conform continued work at this level, or re-designate the level.

Laboratory staff must have specific and thorough training in handling extremely hazardous infectious agents. Laboratory staff must understand the primary and secondary containment practices, containment equipment, and laboratory design characteristics. All laboratory staff and supervisors must be competent in handling agents and procedures requiring BSL4 containment. The laboratory supervisor in accordance with institutional policies controls access to the laboratory..

All procedures within the facility with agents assigned BSL4 are conducted in the Class III biological safety cabinet or in Class I or II biological safety cabinets used in conjunction with one-piece positive pressure personnel suits ventilated by a life-support system.

The maximum containment facility consists of either a separate building or a clearly demarcated and isolated zone within a building.
For additional detailed standards refer to the NIH Guidelines and the BMBL.