Four biosafety levels (BSLs) have been allocated to laboratory practices involving hazardous biological agents, with specific biocontainment measures for each. While low risk level 1 procedures can be performed at an open bench, BSL 2, 3 and 4 procedures must be done in a microbiological safety cabinet.
We at Contained Air Solutions Ltd (CAS) supply solutions for all four levels of biocontainment. While a biohazard hood is not required for level 1 work, a vertical or horizontal laminar air flow cabinet can be useful for protecting the experimental area from airborne contamination.
Precautions to be taken in the BSL-1 laboratory
Any microbiological agent that does not consistently cause illness in healthy human adults can be handled at BSL-1 level. However, it is still essential to follow good microbiological practice with respect to the wearing of protective clothing, disposal of sharps, mechanical pipetting, hand-wash procedures and so on.
Although BSL-1 procedures can be performed in an open environment, they should be carried out in a way that minimises splashes and aerosols. All work surfaces and equipment should be decontaminated following use, and all infectious or potentially infectious materials should be decontaminated prior to disposal. While it is not necessary to separate the laboratory from the rest of the building, it should have closing doors.
BSL-2 and BSL-3 facilities
BSL-2 agents are those posing a potential, but moderate threat to human health, or those that are difficult to contract by inhalation. In addition to the BSL-1 practices above, certain special measures must be taken, including:
• Staff to be specifically trained in the handling and use of pathogens
• Special precautions when dealing with contaminated sharps, solutions, equipment and clothing
• Full protective clothing, including disposable gloves, gown and eye and face protection to be worn, and removed before leaving the room
• The room should be equipped with an autoclave or similar decontamination device for disposal of waste
• All procedures in which infectious splashes or aerosols may be generated must be conducted in a Class 1 or Class 2 microbiological safety cabinet. This includes pipetting, mixing, inoculation of animals, sonicating, centrifuging, removal of infectious tissues and opening infectious vials
• BSCs should be installed away from doors, windows, lab ventilation systems, areas of heavy traffic and other places which could affect the laminar air flow
A recirculating cabinet is one in which the exhaust air passes through an HEPA filter and is then returned to the lab environment rather than outside. It is safe to use a recirculating Class 2 biohazard cabinet in a BSL-2 laboratory, or alternatively the cabinet can be exhausted directly to the outside through a hard connection, or through the laboratory exhaust system via a canopy or thimble connection.
Laminar flow solutions for Level 3 biocontainment
BSL-3 agents are those that pose a serious or fatal risk to health through inhalation, but for which treatment is available. Since this includes diseases like tuberculosis and anthrax, extreme caution must be exercised.
All BSL-3 agents must be handled within a microbiological safety cabinet with non-recirculated exhaust air. The room should be at negative pressure and physically isolated from the corridor, with entry through a double-door anteroom with sealed access. In certain cases, a BSL-2 room with directional laminar air flow may be acceptable.