Commissioning is performed prior to occupying new lab facilities to ensure that systems are operating as specified. Many organizations also repeat commissioning, or at least some portion thereof, at regular intervals to ensure continued proper operation of building systems. This “re-commissioning” is a good practice to guarantee that all building systems continue to function as required.
One of the most important systems considered in the commissioning process for laboratory facilities is the HVAC system. This is where commissioning and certification have a vital overlap and interdependence. Proper HVAC design and operation is crucial to the proper operation of a biosafety cabinet. While the majority of biosafety cabinet installations simply return cabinet exhaust to the room, they may still impact, or be impacted by, the function of the HVAC system.
From a heating and cooling standpoint, a typical 4-foot Class II Type A2 cabinet may generate 1,000 to 3,000 BTUs/hr. Air conditioning and heating systems should be verified to maintain the desired environmental conditions when biosafety cabinets are in operation, as well as when cabinets are turned off.
More crucial to the safety of laboratory workers and the integrity of aseptic work processes is the possible impact of air currents in the room on the performance of the biosafety cabinet itself. The location of room air supplies and returns is critical as cross-drafts may negatively affect the performance of biosafety cabinets. This dependency should be taken into account when designing room air ventilation and should be verified during the commissioning process.
Another level of complexity is introduced when biosafety cabinets are vented to the outdoors via the building exhaust system. With such an installation, the biosafety cabinet itself becomes the first piece of the system ductwork and needs to be designed and tested as such. In addition to the possible impact of cross-drafts, the commissioning process for biosafety cabinets should also verify that the required exhaust and room supply air to operate the biosafety cabinets are available and that HVAC controls are interfaced with the biosafety cabinet controls.
Supply air requirements for biosafety cabinets are often overlooked. However, they can be just as critical as exhaust air requirements to proper cabinet function. Whatever volume of air is exhausted from the biosafety cabinet must also be supplied to the room in order to avoid “starving” the cabinet of air. The supply air available to the BSC should be verified as well as the supply air to maintain desired room pressurization and air exchange rates. A biosafety cabinet cannot be certified if a lack of supply air causes a low or inconsistent inflow or downflow velocity.
Biological safety cabinets are constant volumetric airflow devices, and the fan energy to exhaust the cabinet must be provided by the building exhaust system. In addition to the exhaust airflow, the static pressure requirements for hard-connected Type B cabinets are relatively high. This is due to the resistance added to pull air through the cabinet and its exhaust HEPA filters. For canopy-connected Type A cabinets, the cabinet blower overcomes the resistance of the exhaust filter; however, sufficient exhaust flow is still important. Biological safety cabinets will not function properly and cannot be certified if the exhaust flow or static pressure is not sufficient (or potentially if either is too high).
Low exhaust flow can lead to a loss of containment at the front access opening of the biosafety cabinet and pose a risk to workers. As indicated by NSF 49, exhausted biosafety cabinets should have airflow monitors that alarm when the exhaust flow is too low. This feature is required for hard-connected Type B cabinets and should be considered as good practice for canopy-connected Type A cabinets. The alarm function should be verified during commissioning, as well as for certification. It is often desirable, or even required, to control the biosafety cabinet and HVAC systems in concert, and verification of any such interlocks should be included in the commissioning process. Interlocks in the control allow the room to maintain the required pressurization, air changes, and exhaust flow when the cabinet is in operation, as well as when the cabinet is turned off.
Many of the problems encountered in the field regarding proper operation of biosafety cabinets could be avoided if a thorough commissioning process were followed. The commissioning process should include documentation and verification of the requirements for biosafety cabinets as they relate to the building’s HVAC systems. Field certification can be successfully completed only after the HVAC requirements for biosafety cabinets have been verified through commissioning.
Review the protection levels and key features of Class II Biosafety Cabinets in this free guide. It includes an easy-to-read chart explaining how the types of Class II cabinets differ and graphics illustrating the supply, exhaust and recirculation airflow patterns that classify Type A1, A2, B1 and B2 cabinets.