My question is: If there is a fire in a laboratory, is it best to turn on, or leave on, ventilation hoods or to turn them off (or otherwise lower sashes in order to minimize the effectiveness of the hood?)
I can find no clear guidance on this after reading (not completely!) the NFPA Fire Protection Handbook. (I am also a volunteer firefighter for many years; this informs my thinking below.)
My inclination is to recommend that hoods be left on, or turned on if easy or convenient to do so in the process of evacuation. (Caveat: If there is a significant fire IN the lab that I am in, or my students are in, the rule is: GET OUT NOW! Life preservation takes priority over property preservation. The situation I pose is that if the fire alarm goes off and there are no signs of fire in the immediate area, what is the best course of action on the way out?) My thinking is that leaving hoods on will help considerably with the removal of smoke and heat in a laboratory. Smoke kills occupants and smoke and heat removal are important for effective firefighting, assuming that firefighters are inclined to attempt an interior attack on a lab fire.
Leaving hoods on also draws in make-up air which can foster fire growth but this must be weighed against the value of smoke and heat removal.
The assumption is that the ductwork construction is non-combustible (NFPA 91, Section 4.2) and adequately sealed so that hot gases do not leak and cause fire spread.
I already know that the “best” answer to this is to consult with the local AHJ and do what they want to be done. I’d like to seek the guidance of the SAFETY group, as well.
David C. Finster
Professor of Chemistry
University Chemical Hygiene Officer
Department of Chemistry
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