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VENTILATION HOODS AND OTHER ENGINEERING CONTROLS

"A requirement that fume hoods and other protective equipment are functioning properly and specific measures that shall be taken to ensure proper and adequate performance of such equipment." 29 CFR 1910.1450(e)(3)(iii)

The ventilation hood is the primary laboratory ventilation control system for protecting laboratory personnel from exposure to hazardous chemicals. The hood itself is one component of the system which consists of a working chamber, an exhaust system, proper hood location, make-up air to the hood, a hood monitoring system, hood operating parameter, routine performance surveys, and system maintenance.

Air flow patters are affected by many factors, including traffic patterns, room make-up air, doorways, room size, hood location, work practices, objects inside the hood, baffle adjustment, and sash opening. These are considerations for design, installation and use of ventilation hoods. Ideally, the air should flow into the lab from doors, hallways and the room air supply and exit the room through the ventilation hood. There should not be any turbulence at the hood face which could spill contaminated air into the room. All areas of the open hood face should have a velocity sufficient to draw room air and not spill contaminated air from the hood.

Standards of performance for ventilation hoods are set forth by ANSI/AIHA Z9.5 and OSHA 29 CFR 1910.145(e)(3)(iii). The average face velocity of optimally performing hoods should be between 80 and 120 feet per minute (FPM) when measured with the sash raised to the 18" mark. These average face velocities and the date of survey will appear

on the inspection sticker located on the front of the ventilation hood. Ratings are also stated according to the hood performance as follows:

1. All work involving hazardous chemicals should be performed inside a ventilation hood.
2. Before work begins, check to be sure the hood fan is turned on.
3. Check the airflow by observing the monitor, or in the absence of a monitor use a "kimwipe" taped to the open sash.
4. Check the inspection sticker to determine if the hood has been currently (yearly) inspected and what performance rating it was given. If observable questions arise about inspection or current hood performance, contact the Center for Environmental Health and Safety (CEHS for assistance.
5. Ventilation hoods should be used with the sash positioned at 18" or lower when possible for optimal performance and as a protective shield.
6. All equipment and materials should be located at least 6" back inside the hood from the sash face.
7. Large items should be elevated at least 2" from the hood base to insure airflow to the baffle opening at the rear interior base of the hood
8. Do not use the ventilation as a storage cabinet. Excessive storage can obstruct air flow and cause areas of low air velocity at the face opening.
9. Do not extend face or head inside the hood.
10. Minimize traffic and other sources of cross drafts (i.e. open windows, doors, fans, etc.) which may pull contaminated air from the hood.
11. When using electrical equipment in a hood take extra precautions to prevent spark sources from causing fire or explosion. All electrical connections should be made outside the hood.
12. Do not use perchloric acid heated above ambient temperature in a ventilation hood unless it is a specifically designed perchloric acid hood with a wash-down system.
13. Emergency plans should be understood by all hood users in the event of an unexpected occurrence such as fire or explosion in the hood.
14. If assistance is needed regarding the safe operation of a ventilation hood, contact the Center for Environmental Health and Safety.

Copyright © 1994-2003 Southern Illinois University
Center for Environmental Health and Safety
Phone: 618-453-7180
E-mail: info@cehs.siu.edu