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Definition of Terms

Laminar Flow
Laminar flow is unidirectional air moving at a steady velocity along parallel lines. Laminar flow cabinets may or may not be biological safety cabinets.

HEPA Filter
High efficiency particulate air filter designed to remove particles, including microorganisms, from the air. HEPA filters are effective at trapping particulates and infectious agents, but not at capturing volatile chemicals or gas. Only certain classes of biological safety cabinets that are exhausted to the outside can be used when working with small amounts of volatile chemicals.

Laminar Flow Clean Benches
These are not biological safety cabinets and offer no worker or environmental protection. Clean benches must never be substituted for biological safety cabinets. Air is blown at the worker exposing them to whatever is present on the bench. Clean benches should not be used for work involving cell cultures, toxins, volatile chemicals, infectious materials, or materials that may cause hypersensitivity to the worker - such as animal dander.

Laminar flow clean benches can have either horizontal or vertical airflow (see figure). HEPA-filtered air is discharged accross the work surface to protect product on the bench from contamination. Vertical flow clean benches may have a sash similar to a biological safety cabinet but air is discharged at the worker under the sash. There is no air intake grill below the sash.

Biological Safety Cabinet
Biological safety cabinets are often referred to as "tissue culture hoods" or "laminar flow hoods". Biological safety cabinet is the correct term. All biological safety cabinets use HEPA filters to treat exhaust air. Class II cabinets filter both exhaust and intake air to protect the worker and the environment from contamination as well as to protect product in the cabinet. See Types (Classes) of Biological Safety Cabinets to learn more about the different classifications of biological safety cabinets and how to select the correct cabinet for your work.

Chemical Fume Hoods
Chemical fume hoods are used to protect workers from exposure to volatile chemicals. Neither the intake or exhaust air is HEPA filtered. Infectious materials should not be used in chemical fume hoods. These hoods are part of the facility and are tested annually by DEHS (Environmental Health and Safety).