Biosafety Cabinet Window Sash Level

Class II Biological Safety Cabinets, or BSCs, provide vital personal, product, and environmental protections in the laboratory setting. BSCs go through a certification process to meet the NSF/ASNI 49 and/or EN 12469 standards. However, operating errors can negate the carefully designed protections. Laboratory workers must operate at the proper window sash level to prevent potential contamination.

Window Sash’s Airflow Impact

Biosafety cabinets have a movable or fixed window on the front that protects workers from the active work area. This is called the window sash. A cabinet’s certification will be based on having the window sash positioned at specific heights due to the potential impacts on downflow and inflow velocities. Current industry standards will provide a workable window sash height of 8, 10, or 12 inches (203, 254, or 305 mm).

Most cabinets will have some type of notification of where the window should be placed during work activities. New cabinets and even some from the 1990s will have a window sash alarm if not aligned properly.

Before a BSC leaves the NuAire factory it will go through testing that includes airflow balancing placing the workable sash height at the level you requested 8, 10, or 12 inches (203, 254, or 305 mm). A professional in the field will then certify your cabinet after installation at the window sash height you requested.

Window sash positioning is among the most vital information about biosafety cabinets and is as important as proper laboratory sterilization. The Biosafety Cabinet works to keep contaminated air from entering the work zone and into the laboratory as well as minimize cross-contamination within the work zone through unidirectional air.

The accuracy of this biosafety process depends on the cabinet maintaining a balance between inflow and downflow velocities. When working within the cabinet and not placing the cabinet’s window sash at the certified working level you compromise airflow balancing. If the inflow velocity is too strong, contaminated air can enter the sterile work area and contaminate the work. Excessive downflow velocity can push contaminated air from inside the cabinet out into the laboratory without filtering as well as create turbulent air at the work surface causing product contamination. The result of improper airflow balance can be seen below.

Not working at the proper window sash height can throw off the airflow balance within a Biosafety Cabinet.

Potential Risks: Contaminated Air and Work Space

Unbalanced airflow velocities pose heightened risks when dealing with infectious materials that can pose serious safety risks to lab workers. However, the imbalance can also destroy complex, controlled experiment conditions such as those used in growing cell cultures.

Proper window sash positioning can reinforce worker diligence on properly interacting with the cabinet. The easy access allows the operating worker to use careful arm movements that help minimize the amount of room air that enters into the cabinet. A sash that’s positioned too high or low can leave the worker constantly reaching up and down, churning the interior air, and increasing the chance of laboratory equipment handling errors, and introducing risks of contamination and splattering.