A biosafety cabinet (BSC)—also called a biological safety cabinet or microbiological safety cabinet is an enclosed, ventilated workspace for safely working with materials contaminated with (or potentially contaminated with) pathogens.  The primary purpose of a BSC is to serve as a means to protect the laboratory worker and the surrounding environment from pathogen as well as to maintain the sterility of materials inside (the "product"). The U.S. Centers for Disease Control and Prevention (CDC) classifies BSCs into three classes with Class II cabinets provide both kinds of protection (of the samples and of the environment) since makeup air is also HEPA-filtered. There are five types: and type's requirements are defined by NSF International Standard 49.

Type A2 cabinet, formerly known as Type A, has a minimum inflow velocity of 100 ft/min. The downflow air, considered contaminated, splits just above the work surface (the BSCs smoke split) and mixes with the inflow. This air is drawn, through ductwork, up the back of the cabinet where it is then blown into a positive pressure, contaminated plenum. Here, the air is either recirculated, through a HEPA filter, back down over the work zone, or exhausted out of the cabinet (also through a HEPA filter). Sizing of HEPA filters and fan system are used to balance these air volumes. Traditional Class II BSC designs use single fan systems that, are generally able to maintain total airflow but not the balance of inflow and downflow.

Should the downflow and exhaust filters load at different rates and uneven loading, the inflow could steadily increase while the downflow steadily decreases (Figure 3: High inflow / low downflow). Uneven loading could also go the other way leading to loss of containment (Figure 4: Low inflow / high downflow). The compensating single fan unit does not maintain the balance of inflow and downflow necessary for both personal and product protection. All Thermo Scientific biological safety cabinets use a dual fan system with separate downflow and exhaust fans. Downflow fans provide downflow, and exhaust fans provide inflow with independent monitoring using ebm-papst Inc. DC motor-based BSC with world renowned for reliability, these motors are estimated for >100,000 hours (>11 years) of use – double the lifespan of other DC motor designs.

Independent and real time control of inflow and downflow is an excellent way to support continued protection of you and your work. SmartFlow Plus technology compensates both inflow and downflow fan. It actively maintains personal and product protection through real time compensation to maintain inflow and downflow.

All Thermo Scientific Class II (Type A2) BSCs incorporate a pressure sensor-based independent airflow monitoring system called Digital Airflow Verification (DAVe). Separate sensors measure pressure change across the downflow and exhaust HEPA filters, ensuring accurate overall measurement of both airflows. These measurements are converted into an audible and visual alarm alerting the user to an airflow imbalance.

Thermo Scientific BSC’s combined approach of superior airflow control by independent DC motors (SmartFlow Plus technology), plus independent pressure sensor-based airflow alarms – DAVe – ensures the highest levels of worker safety and product protection.

Additional Resources: US. Centers for Disease Control and Prevention; U.S. National Institutes of Health (2000). Primary Containment for Biohazards: Selection, Installation and Use of Biological Safety Cabinets (PDF). U.S. Centers for Disease Control and Prevention.