Which class of biological safety cabinet features 70% recirculated air and 30% exhausted air through HEPA?

Class II-A1 biological safety cabinets are designed to provide personnel, product, and environmental protection by utilizing a combination of air filtration and airflow techniques. In a Class II-A1 cabinet, approximately 70% of the air is recirculated within the cabinet after being filtered through a HEPA (High-Efficiency Particulate Air) filter, while the remaining 30% is exhausted from the cabinet to the outside environment after passing through another HEPA filter. This setup creates a balanced airflow that helps to maintain a sterile environment for handling biological materials, ensuring that contaminants do not escape into the lab atmosphere.

This design is crucial for labs that need to work with various pathogens or sensitive biological agents, allowing for safe manipulation while minimizing risks. The recirculation of filtered air also helps in maintaining consistent airflow within the cabinet, further protecting both the user and the samples being handled.

Other classes of biological safety cabinets follow different air circulation and filtration methods, which do not fit the described percentages for the Class II-A1 cabinet. For instance, Class I cabinets do not recirculate air into the work area, and Class III cabinets are entirely enclosed and operate under negative pressure with filtered exhaust, thus differing significantly in design and function from Class II-A