Part 3 – Containment laboratory design features (BSL3/CL3)

When dealing with additional risks, such as working with risk group 3 pathogens, there are specific design and containment features that can be implemented to mitigate the heightened risks. This level of containment is commonly referred to as BSL3 or CL3 in certain countries. These features come with a significant cost and should only be incorporated if deemed necessary based on a thorough risk assessment.
Given the increased risk level, the facility should be situated either within a BSL2 facility or in a separate building altogether. Access to this facility must be restricted to a select few individuals. Therefore, card access systems are utilized to provide easier control and tracking. A proximity sensor reads an access card that is presented or swiped for entry. Exterior doors may also feature a personal identification number (PIN) pad for additional security measures.

Furthermore, there is heightened signage on the exterior of the facility indicating its status as a high containment laboratory, along with the additional personal protective equipment (PPE) required for entry.
One common feature found in high-risk spaces is the presence of an ante-room between the exterior and interior of the laboratory. This area is typically separated by two closed doors, which may be interlocked to ensure only one can be opened at a time. This ante-room can be utilized as a changing room or an exit shower, depending on the results of a thorough risk assessment. It plays a crucial role in maintaining the integrity of the laboratory by preventing contamination from entering or exiting the facility. The ante-room serves as a transitional space, offering a buffer between the laboratory environment and the outside world and is crucial for maintaining negative pressure in the laboratory.

Due to the higher risk, additional personal protective equipment (PPE) is now required before entering. This necessitates the need for extra storage space and designated areas for donning and doffing the equipment. For instance, workers may need to wear a powered air purifying respirator, which must be charged and stored daily. This extra space is often designed into the area in or near the anteroom. It is essential that all support spaces for using additional PPE are carefully integrated into the laboratory design. This includes provisions for both male and female changing rooms, as well as clean and dirty change rooms if a shower out is deemed necessary based on the risk assessment.

 One crucial feature often incorporated into higher containment facilities is the utilization of negative pressure rooms, which facilitate a strong inward directional airflow. This feature goes beyond the previously mentioned inward directional airflow. By employing a ducted ventilation system that utilizes supply and exhaust fans, air is strategically moved from the outside (potentially the hallway) through cascading zones of progressively increasing negative pressure. This results in a controlled airflow from lower containment areas to higher containment areas. Achieving this can be accomplished by either creating negative pressure within the laboratory or by adjusting the volumetric offset of supply and exhaust air between the laboratory and hallway. While this feature comes at a significant cost, it is essential in scenarios where potential aerosols may be released within the laboratory or animal room.

To ensure that infectious aerosols are not released from the laboratory or animal room, exhaust air is often HEPA filtered. These are large filters that need to be tested and certified before use, monitored during use and changed as needed. They are installed in specialized HEPA filter housing that allow for isolation, fumigation and in-place testing. They are commonly found in BSL3 laboratories or animal rooms where high-risk agents are being used.

When implementing directional airflow, it is imperative to consider the necessary air changes per hour. Air changes per hour indicate how many times the entire volume of air within a room is exchanged in an hour. While there is no fixed or definitive number for air changes per hour, they typically range from 2 to 15, depending on factors such as heat load, potential aerosol generation, and odors. Laboratories with a substantial amount of equipment may require a higher number of air changes per hour to effectively dissipate heat. Similarly, in animal rooms where animals roam freely, the air exchange rate is typically elevated due to odors, ammonia, and potential aerosols present in the air.

In order to minimize the risk of hand contamination with high-risk materials, laboratories and animal rooms now require hands-free sinks to be installed in the ante-room or at the room exit. This eliminates the need to touch potentially contaminated taps, reducing the risk of re-contamination. Hands-free sinks can be operated by foot, elbow, knee, or electronically, as shown in the image of someone using a foot-operated sink.

 Contaminated waste, both solid and liquid, from high-risk areas should be sterilized promptly. Utilizing a pass-through autoclave for autoclaving waste outside of high-risk areas is the most effective method. When it comes to animal waste and carcasses, it is ideal to have a system in place for direct disposal into an incinerator or alkaline digestor. If this is not feasible, the waste must be contained and transported to an onsite disposal facility.

In high-risk spaces where aerosols may be generated, fumigation of the room with gas is a recommended practice to eliminate pathogenic organisms. This is particularly common in animal rooms. Designing features that allow for gas injection into the room, such as gas injection ports in a plexiglass wall, doors or walls are crucial. Some facilities even incorporate gas generators into the room design during construction.

When dealing with additional risks, such as working with risk group 4 pathogens, it may be necessary to incorporate additional facility features. This level of containment is known as BSL4 or CL4, involves maximum containment measures. Constructing and maintaining such facilities is extremely costly and is only done by few countries. As a result, this topic falls outside the scope of this biorisk management course and will not be covered.

In summary, the diagram provided by the WHO illustrates the various facility features that can be implemented at different biocontainment levels. The table displays the biosafety levels (1, 2, 3, and 4) along the top, and the corresponding additional features recommended for each level along the left-hand side. For instance, at biosafety level 1, very few additional features are necessary, while at biosafety level 4, all facility features are mandatory.
It is evident that as the level of biocontainment increases, so do the facility features, as well as the associated construction and maintenance costs. It is important to remember that these biosafety levels are merely guidelines, and in practice, a continuum of containment levels can be established based on the chosen risk mitigation procedures.

In order to ensure the functionality of facility features, it is imperative that they are tested and certified according to their design requirements. This includes assessing ventilation rates, determining air changes per hour, validating resistance to chemical degradation, and testing door interlocks. High containment facilities in particular require thorough testing and certification before they can be operated, as well as annual recertification.

In conclusion, it is crucial to recognize that facility design plays a vital role in biorisk management by supporting and enhancing other safety and security controls. Proper facility configuration and design enable individuals to perform tasks safely and effectively. Careful consideration should be given to layout and design features, ensuring that equipment such as autoclaves, biosafety cabinets, sinks, and waste receptacles are strategically placed. While basic BSL2 laboratory design features are suitable for most clinical and research work, additional features may be necessary depending on the level of risk.

Thank you for participating in this lesson on how biosafety facility design contributes to biorisk management. Please proceed to the quiz to reinforce your understanding of the key concepts discussed.