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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. If your fume hood is not equipped with an air flow indicator/alarm, 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. 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.

Note: There is no specific OSHA requirement for fume hood flow monitors, although paragraph (e)(3)(iii) of the Laboratory Standard, 29 CFR 1910.1450 does require that "fume hoods and other protective equipment are functioning properly". Some states do require airflow monitors. For example, Title 8 of California Code of Regulations 5154.1 requires "quantitative airflow monitor that continuously indicates whether air is flowing into the exhaust system during operation." This does not specify the type of device, which can range from a simple liquid manometer to an electronic feedback system. Other non-governmental standards call for airflow monitors. These include: ANSI/ASHRAE Standard 110 - Method of Testing Performance of Laboratory Fume Hoods NSI/AIHA Standard Z9.5 - Laboratory Ventilation NFPA 45, 2004 - Standard on Fire Protection for Laboratories Using Chemicals which requires a "...measuring device for hood airflow shall be a permanently installed device and shall provide constant indication to the hood user of adequate or inadequate hood airflow."

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.

Books Available

• "Laboratory Fume Hoods: A User's Manual", Paperback, 123 pages, 1993. Estimated price $105.00. Info and/or order.
• ANSI/AIHA Z9.5-2003: Laboratory Ventilation", Hardcover, 111 pages, 2000. Estimated price $83.00. Info and/or order.
• "Dust and Fume Control: A User Guide, Second Edition", Hardcover, 158 pages, 1992. Estimated price $57.50. Info and/or order.
• "Laboratory Biosafety Manual", Paperback, 186 pages, 2005. Estimated price $50.00. Info and/or order.
• "Guidelines for Laboratory Design: Health and Safety Considerations, 3rd Ed", Hardcover, 454 pages, 2001. Estimated price $179.55. Info and/or order.

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. Finally, let's remind everyone to always ensure your fume hood is working properly before performing experiments. In 2009, a worker in Canada died when he performed a chemical reaction in a fume hood that had been deactivated for maintenance.

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Further Reading

• Darthmouth College and NIH have produced an excellent 7+ minute video animation of fume hoods and their operation, and it's available in 8 languges.
• 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.