> 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

Ralph Stuart CIH

Chemical Hygiene Officer

Department of Environmental Health and Safety

Cornell University

rstuart**At_Symbol_Here**cornell.edu