Biosafety Cabinet vs. Fume Hood

Biosafety cabinets use HEPA-filtered, vertical unidirectional airflow within the work area to protect personnel from exposure to airborne biohazards and other potentially harmful particulates within the cabinet. Product protection is achieved when this vertical unidirectional downflow air combines with suction below the intake grille and prevents outside airborne contaminants from entering the workspace. Finally, the environment is protected because air is HEPA filtered before being exhausted.

Fume hoods protect users from toxic or volatile chemicals by continuously delivering airflow away from the user to the work area. All air is exhausted from the cabinet and is not HEPA filtered. No personnel or environmental protection is provided.

HEPA filters trap particulates only, and are completely porous to gases and vapors, so for biological particulate hazards, or chemicals that don’t produce vapors (like powders) biosafety cabinets (class II) provide the same protections. However, some procedures demand the use of volatiles. The quantities of volatiles must be limited due to the potential of electrical spark ignition within the cabinet’s work zone.

Because fume hoods are used primarily for chemicals, they must meet UL requirements for Material Flammability and Effectiveness of Airflow Characteristics (UL 1805). Under UL 1805, laboratory hoods and cabinets, including fume hoods, are investigated for fire, electrical and mechanical risk of injuries. Most biological safety cabinets are not classified under this standard because they are not typically used for large quantities of volatile chemicals.

Performance of a fume hood is regulated through ANSI/ASHRAE 110-1995, which specifies a quantitative test procedure to evaluate the performance (containment capabilities) of a laboratory fume hood. NSF International (The National Sanitation Foundation) conducts tests on biological safety cabinets to ensure the products meet minimum standards for cabinet classifications devised by NSF.

Today, new design innovations have paved the way for a new hybrid cabinet, a Class II Type B2 total exhaust biosafety cabinet that is also a fume hood.

Total exhaust cabinets are widely used in toxicology laboratories and similar applications where chemical effluent is present and clean air is essential. The requirements identified in UL 1805 do not place specific restrictions on the quantity of volatiles allowed; however, because biological safety cabinets typically have electrical outlets or other electrical controls within the work area, the quantities of volatiles must be limited due to the potential of electrical spark ignition within the cabinet’s work zone.

By simply offering a configuration where the electrical outlets and controls are located on the outside of the cabinet, the biological safety cabinet may also be used (and UL listed) as a fume hood. Before using a total exhaust biological safety cabinet as a fume hood, just ensure that it meets the UL requirements for Electrical/Mechanical Safety (UL 61010‐1), the UL requirements for Material Flammability and Effectiveness of Airflow Characteristics (UL 1805), and that it has been tested in accordance with ANSI/ASHRAE 110‐1995.

While the responsibility for evaluating specific hazards rests with the end user and proper use should be determined by a professional industrial hygienist or safety officer, here are some general recommendations:

Select a Class II, Type B2 cabinet when you require:

• Product, personnel and environmental protection.
• Total exhaust to the outside through hard‐duct and a HEPA filter.
• Procedures require the use of hazardous chemicals that vaporize as an adjunct to the microbiological work.

Add on a Fume Hood option when you require:

• Primary biological and chemical (small quantity) containment is required.
• Procedures require the use and containment of volatiles, including the removal of vapors, mists, gases, and particulate matter from the work area.
• You require that the total exhaust BSC be classified with UL 1805 and ANSI/ASHRAE 110-1995.

Select a Fume Hood when you do NOT require:

• Product or environmental protection.

Which Biosafety Cabinet Should You Choose?

Still not sure which containment equipment will work best for you? Find out with our biosafety cabinet decision map.

Take the guesswork out of BSC purchases…
Try Baker‘s Biological Safety Cabinet Decision Map