The air from a class II-B1 biological safety cabinet is what percentage recirculated through a HEPA filter?

In a Class II-B1 biological safety cabinet, the air is indeed recirculated through a HEPA (High-Efficiency Particulate Air) filter, but the proportion is generally around 70% recirculated and 30% exhausted. However, the correct choice regarding the context of recirculation percentages is 100% exhausting as this type of cabinet is designed to provide operator and environmental protection while ensuring that the biological agent is contained.

In a Class II-B1 cabinet specifically, all of the air is typically exhausted and only a small portion is recirculated after being HEPA-filtered. The main function of these cabinets is to maintain a sterile environment for the samples being handled, thus their HEPA filtration is key. The concentration of recirculated air is a secondary aspect compared to the primary safety function, which is why the answer reflects a percentage focused on exhaust rather than recirculation.

Understanding the handling and flow dynamics in a Class II-B1 biological safety cabinet is vital for maintaining proper safety protocols in laboratories, particularly when working with potentially hazardous materials.