Exposure controls include equipment and procedures designed to minimize inhalation, skin absorption, or ingestion of hazardous materials. Fume hoods and biosafety cabinets are two common pieces of lab equipment that can greatly decrease the potential for inhalation exposures to hazardous chemicals or biological agents. Although they may look similar, laboratory fume hoods and biosafety cabinets are designed and function very differently and must be used appropriately to afford the user protection. Many additional hazard-specific or process-related controls are available.

A properly operating and correctly used fume hood can reduce or eliminate exposure to volatile liquids, dusts, and mists. It is advisable to use a laboratory hood when working with all hazardous substances. In addition, a laboratory hood or other suitable containment device must be used for all work with “particularly hazardous substances.”

The biosafety cabinet (BSC) is an essential piece of safety equipment for many laboratories conducting biological research. The BSC is designed to provide both personnel and environmental protection from potentially infectious materials and human pathogens. BSC’s are manufactured in three different classes (Class I, II and III). The common feature in all BSCs is the high efficiency particulate air (HEPA) filter. HEPA filters can remove particles down to 0.3 microns with 99.97% efficiency and will trap most bacteria and viruses. Vapors (from ethanol, formalin, etc) and gases will not be captured and removed by the HEPA filter.

Class I Biosafety Cabinet

Provide personnel and environmental protection, but do not provide a sterile work surface. Airflow in a Class I BSC is similar to a chemical fume hood, with air being drawn away from the worker and across the work surface. The exhaust from the cabinet is HEPA filtered and this protects the environment. Class I BSC are useful for work that requires containment but not product sterility.

Class II Biosafety Cabinet

Provide personnel, product and environmental protection. Air is drawn around the worker into the front grill of the BSC, providing operator protection. HEPA filtered sterile air flows down onto the work surface, minimizing the potential for cross-contamination. Exhaust air passes through another HEPA filter before being released into the surrounding environment. Class II units are further divided into four types; A1, A2, B1, and B2, based on the percentage of air that is recirculated and exhausted.

Class III Biosafety Cabinet

Class III BSCs are designed to provide maximum protection to the worker and the environment. Sometimes called Class III glove boxes, these units are gas-tight enclosures with a non-opening view window. Intake air is filtered through a HEPA filter and exhaust air passes through two HEPA filters before being released.