Selecting a biological safety cabinet (BSC) is a critical part of setting up or upgrading any laboratory. The first step is to perform a detailed risk assessment with a certified biosafety safety professional (CBSP) or industrial hygienist who has knowledge of the risk levels associated with specific biological materials and chemicals that may be used. A qualified biosafety professional should have training and field experience that includes methods used to control biohazards, as well as knowledge of the design, application and testing of BSCs. After determining your specific risk, the next step is to assess how those risks will be fully met by the proper class and type of biological safety cabinet.
Classes
There are three class of BSCs, which all offer different levels of protection to personnel, environment and materials.
Class I BSCs offer personnel and environmental protection only. Personnel protection occurs by constant movement of air into the cabinet and away from the user. Meanwhile, the environment is protected by filtering air before it is exhausted. A Class 1 cabinet does not protect the product from contamination. As such, a Class 1 cabinet is suitable for work involving low to moderate risk agents where there is a need for containment, but not product protection.
Class II biosafety cabinets are the most commonly used types and offer protection of personnel, the material, and the environment through HEPA filtration, laminar airflow throughout the work surface, and an air barrier at the front of the cabinet by use of a vacuum. HEPA filters effectively trap airborne particulates, removing potentially infectious agents, but volatile chemicals and gases pass through unimpeded. Use of materials that generate gases or vapors require an exhaust connection to a facility exhaust system.
Class III cabinets, also known as glove boxes, provide maximum protection for the environment and its users. They are designed to handle highly infectious microbiological agents, unknown agents, and other hazardous applications. Exhausted HEPA filtered air must pass through two additional HEPA filtered or a HEPA filter and air incinerator before being discharged back into the outdoor environment.
In addition to class, lab managers must consider multiple aspects regarding the lab space where the BSC will be housed. Maximum space allotment, especially width, should be evaluated to ensure the cabinet can fit properly within the work space. There should be sufficient room in doorways and hallways to easily move the biosafety cabinet when needed.
A BSC must be installed away from doors, fans, high traffic patterns, and any device that could disrupt its airflow patterns. Ideally, a BSC should be installed in a location with a minimum clearance height of at least 6 inches above and to the side. This ensures that the air re-circulated to the laboratory is not disrupted. BSCs that are not connected to an exhaust system, however, should have a clearance area of at least 12 inches from the face filter and any overhead obstructions. In a BSL-3 and 4 lab, exhausted air is directed outside the building. In this case, as long as the building's exhaust system is used to bend a ducted BSC, the system should have sufficient capacity to maintain the exhaust flow if changes in the static pressure within the system occur.
Ergonomic options
Laboratory facilities, and therefore equipment, are often shared spaces. And as we all know—everyone has their own preferences. When it comes to ergonomics, though, it’s not so much preference as necessity. To ensure each and every researcher that uses a BSC is comfortable and safe, lab managers should look for equipment with as many customizable options as possible.
Height-adjustable equipment is key to avoiding awkward posture positions and consequential pain. When searching for ergonomic options, lab managers should look for equipment that provides the maximum knee/thigh clearance. Combined with an adjustable chair with lumbar support and a footrest, these types of innovations are not only more comfortable but also ensure correct posture. Some manufacturers even offer a variety of base stands from fixed to telescoping and automatically adjustable to add a higher level of personal customization.
Reach is another pivotal concern as a shorter reach into the work zone brings the work area closer to the user, thereby minimizing fatigue. Turntables can help comfortably extend the reach of users up to 12 inches into the back corners of the hood or cabinet. Counterbalance tools are also an option.
An effective work zone and expanded viewing zone also play a role in reducing awkward postures and positions. In addition to a turntable, a BSC that allows the user to access and manipulate the most material with forearms at rest is recommended. The ability to rest forearms and minimize reaching reduces arm, neck and shoulder strain. Additionally, a frameless, polished-edge window allows for greater visibility and better sight lines of the work zone area, resulting in less eye, neck and shoulder strain.
Lastly, lighting in BSCs helps provide an effective work zone. Rather than harsh, bright light, cabinets should have cool white fluorescent lighting that avoids reflection and reduces glare from the stainless-steel work zone. Manager also want to ensure that the lighting is positioned correctly, i.e., externally mounted, so it does not cast shadows on the work zone, nor does it fall right in front of the eye. Electronic ballasts can help minimize heat output within the work zone itself, as well as the overall laboratory.
Lifecycle
A BSC is a long-term investment for your lab—and it can also be a long-term investment for your budget. Like a car, don’t trust the sticker price. Instead, inquire with the manufacturer about the lifetime cost of the BSC—taking into account operating costs, canopy exhaust connection, HEPA filter life and replacement costs, service life, maintenance schedule and costs, etc.
Approximately 20% of the total cost of ownership of a biosafety cabinet is due to HEPA filter replacements. HEPA degrade over time during both proper storage and normal operational service; however, the rate at which the filters degrade remains unknown. In a standard life science laboratory, typical HEPA filter life for a BSC has been estimated at 5 to 7 years.Though, recent studies suggest filter life may be even longer. For example, a 2021 study at the Pacific Northwest National Laboratory characterizes extending the service life of HEPA filters beyond 10 years as “low-risk.”
Filter life depends on a number of proper environmental conditions—controlled variables such as temperature, humidity and flow rate impact filter integrity. Moreover, cumulative hours of operation, the cleanliness of the lab, and the materials being used in the BSC have a large effect on the length of filter life.
For example, NSF requires that a cabinet’s motor/blower be able to handle a minimum pressure drop of 50% without decreasing airflow by more than 10%. A lab with a biosafety cabinet that meets this minimum standard can expect to pay for five $1,500 HEPA filter replacements over the 15-year life of the BSC—translating to about $7,500 over that time. Meanwhile, a HEPA filter in a cabinet with a pressure drop of 180% can last up to 7 years, saving $4,500. Changing/cleaning the pre-filter on a regular basis can also extend the life of a HEPA filter.