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Fume Hood

Definition

A fume hood is a type of local exhaust ventilation system (engineering control). A typical fume hood is cabinet with a moveable front sash (window) made out of safety glass. Air is drawn into the hood under and through the opened sash and is exhausted through openings in the rear and top of the cabinet to a remote point such as an exhaust stack on the roof of the building.

A properly used and properly functioning fume hood exhausts hazardous gases, dusts, mists, and vapors from a confined location and helps protect workers from inhalation exposure.

Additional Info

Key points about fume hoods are:

Fume hoods are not meant to be storage devices (unless specifically designated as such). Storage of incompatible materials and/or hazardous wastes in fume hoods have caused numerous accidents, many of which have caused death or injury. Here is an example of a fume hood fire/explosion that resulted from such sloppiness. Fume hoods are not waste disposals. Do not let organic chemicals evaporate in the hood - use a proper waste bottle. Do not leave uncapped bottles of chemicals or waste in a hood. Never block the air flow. The slats/baffles in the rear of the hood are part of the air flow system. Obstructing these by storing chemicals, apparatus and garbage in the hood can interfere with the safe operation of the hood. NEVER let your hood look like the one shown below!

A typical bench-mounted laboratory fume hood.



Some safe hood usage tips:

1. Check the air flow before and during use. Try holding a small piece of paper near the bottom of the sash to see if air is flowing into the hood in its normal fashion (modern hoods have air flow indicators and safety alarms). If you suspect the hood is not operating properly, do not use it until it has been repaired and certified for use. See Further Reading for links to information about air flow considerations.
2. Do not use perchloric acid in a fume hood unless it is specially designed for this purpose. Explosive perchlorate salts could accumulate in the exhaust system.
3. Never stick your head into the fume hood! Keep the sash between your face and your experiment whenever possible. Keep the sash lowered at all times except when you need to access your experiment/equipment.
4. Position apparatus as far back in the hood as possible. Air flow is not as efficient at the front of the hood.
5. Fume hoods are good at containing fires, explosions etc., but if the potential for an explosion exists, use an auxiliary blast shield as well.
6. Avoid working opposite a fume hood if possible. Dangerous procedures are often carried out in hoods.
7. Remove all unnecessary materials (especially containers of waste or solvents) when performing an experiment/procedure in a fume hood.

Webcast on Chemical Hoods, September 23, 2008 The American Chemical Society's Division of Chemical Health and Safety (CHAS) is pleased to announce that it is co-sponsoring its first webcast with the Campus Consortium for Environmental Excellence (C2E2). The subject of this webcast will be "Chemical Hoods in the 21st Century: Balancing Safety, Adaptability and Energy Use". The webcast will be free for the first 100 registrants and will occur at 1 PM Eastern Daylight Time, Tuesday September 23. CHAS and C2E2 members will be allowed to register immediately; non-members can register after September 1. More information about the contents of the program can be heard in an introductory podcast available on the CHAS web site. After you've had a chance to hear the podcast, you can submit questions that you would like to have answered during the webcast, or you simply join the webcast and ask your questions then.

MSDS Relevance

Some chemicals are so toxic or volatile that they should only be opened in a fume hood or similar safety/exhaust system. If you have chemicals like this at your workplace, OSHA requires that each worker who uses them is trained regarding the hazards, handling, procedures and necessary equipment. Fume hoods are a much more efficient and effective method of containing hazardous materials than a piece of personal protective equipment such as a respirator. OSHA specifically prohibits the regular use of respirators when a local engineering/ventilation control such as a fume hood can be used/installed instead. Remember, fume hoods protect everyone, but a respirator protects only the user.

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Books Available

• "Laboratory Fume Hoods: A User's Manual", Paperback, 144 pages, 1993. Estimated price $66.50. Info and/or order.
• "Methods of Testing Performance of Laboratory Fume Hoods (Ashrae Standards, No 110-1985)", Paperback, 1995. Estimated price $20.00. Info and/or order.

Further Reading

• Laboratory Chemical Hood User's Guide at the U of Louisville includes some "fume hood myths" and fume hood schematics.
• Chemical Fume Hood Handbook at Northwestern University. Includes references.
• Fume Hood standards at the U of KY.
• Fume Hood Validation Program at Colgate University.
• Primary Containment for Biohazards: Selection, Installation and Use of Biological Safety Cabinets at the CDC's Office of Health and Safety.

See also: administrative controls, engineering controls, highly toxic, respirator.

Additional definitions from Google and OneLook.

Disclaimer: The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.