Chemical fume hoods are the primary containment device in the laboratory used to control airborne contaminants generated by experimental procedures. Chemical fume hoods provide personnel protection by means of directional airflow from the laboratory into the hood through the face opening. This airflow reduces the potential for escape of airborne contaminants into the laboratory. Procedures involving volatile chemicals and those involving solids or liquids that may result in the generation of toxic vapors should be conducted in a chemical fume hood rather than on the open bench. Placing a reacting chemical system within a hood, especially with the hood sash closed, places a physical barrier between the workers in the laboratory and the chemical reaction. This barrier can afford laboratory workers protection from chemical splash, sprays, fires, and minor explosions. Hoods should be evaluated before use to ensure adequate face velocities. Hoods are checked by the Safety & Risk Management Office to determine the face velocity. An adequate face velocity for most applications is 100 feet per minute + / - 10%. Hoods with low face velocity <75 feet per minute are posted as "low toxic only" use. Although chemical fume hoods do protect laboratory personnel from exposures to hazardous materials, they must be used properly in order to maximize their effectiveness. The following practices should therefore be observed when using fume hoods:
Most laboratories handle hazardous materials whether radioactive or chemical which can generate harmful concentrations of aerosols, fumes, vapors, etc. within fume hood exhaust air and which can contaminate the surfaces of laboratory equipment. It is essential for the safety of those required to repair fume hoods, fans, motors equipment, etc. that appropriate precautions to prevent exposure to air contaminants be taken and that laboratory equipment be decontaminated. Whenever work is performed on roof vent fans, within fume hood enclosures or on laboratory equipment the following procedures must be followed.
Roof Fans: Prior to starting work laboratory personnel must certify that all sources of harmful aerosols, fumes, vapors, etc. are contained or removed from the hood being serviced and the hoods with roof fans that are adjacent to the one serviced.
Hood Enclosures: Prior to starting work all materials must be removed from the hood enclosure and contaminated surfaces (if any) shall be cleaned by laboratory personnel.
Laboratory Equipment: Prior to starting work all containers of hazardous materials must be removed and all potentially contaminated surfaces cleaned by laboratory personnel. A radiation survey is to be done for equipment, which has been used with radioactive materials.
Plumbing: Chemicals containers stored around plumbing drains or fixtures must be removed by laboratory personnel. If possible flush the drains with plenty of water. Maintenance employees must wear neoprene gloves and chemical goggles.
For a variety of reasons whether it's an electrical problem, mechanical problem, or routine maintenance a fume hood malfunction can occur. In the event that a low airflow alarm should signal or if the personnel recognizes there is low or no airflow from the fume hood; these outlined procedures should be followed.
Fume Hood Out Of Service Sign
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