Interesting commentary David as you have real world experience as a voluntary firefighter. Most fume hoods, in particular VAV hoods, have some form of fume hood monitor/flow alarm on the hood with an “emergency” purge button of sorts to allow the operator to force the hood to max flow, and thus increase the ventilation at the hood and room. There are now also systems that actively monitor the room environment (eg. Aircuity) and also increase the ventilation in the room in the advent of a spill. Essentially what you are recommending is that you don’t enable these purge systems, but allow the responders to assess the situation and respond as they see appropriate?
David A. Rielly, CEM, LEED GA
Global Energy Manager
Novartis Institutes for BioMedical
I’m surely not a ventilation expert, and I’ve never heard of a “purge button” before. However, in addition to Ralph’s question below about the purpose of using such a device, as an volunteer firefighter for 20 years I can view this scenario of a “significant spill” as a situation that should only be handled by emergency responders. Any situation that poses an atmosphere that is not human-friendly and/or a fire/explosion hazard should simply call for an building evacuation with appropriate power shut-downs (to eliminate ignition sources) IF POSSIBLE.
“We found ourselves using the purge buttons a lot to exhaust the room and the hoods in an emergency.”
I’d re-examine protocols to prevent these episodes rather than re-evaluating response options.
“This is to allow a safer environment for emergency personnel to enter the area and do spill clean ups, particularly when the spill happens outside of the hood. “
The firefighters who respond to this will surely be wearing SCBA and have a four-gas meter to check O2/CO/flammables/X (where is likely H2S). It is thoughtful of you to consider them but, frankly, they will mostly ignore you and treat any major spill as a worst-case scenario to protect themselves. Firefighters can’t afford to blindly trust information given to them by dispatch since in some instances it a wrong (even when not intended to be.) The best thing to is to meet the officer in charge of entering crew at the door, give the best information you have, tell them if you think there is any chance that someone is still in the building, and make sure they have master keys. They know what to do after that.
David C. Finster
Professor, Department of Chemistry
University Chemical Hygiene Officer
> We found ourselves using the purge buttons a lot to exhaust the room and the hoods in an emergency.
I'm not clear what hazard is being reduced by this strategy. Are you trying to prevent a fire by keeping the concentration of the spill below the LEL? Or are you trying to control levels below the IDLH? I'm not sure that general ventilation will accomplish these goals, as the spill could be a location in the lab where the ventilation system doesn't effectively clear the air. We are finding significant "dead spots" in many of our lab settings…
My personal opinion is that the ventilation system should not be considered part of the emergency response system, as its value in a specific situation is undeterminable.
Ralph Stuart CIH
Chemical Hygiene Officer
Department of Environmental Health and Safety
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