From: David C. Finster"
Subject: RE: [DCHAS-L] Chemical Safety headlines from Google (24 articles) Date: October 26, 2011 4:03:37 PM EDT Ii usually refrain from perhaps stating the obvious, but the comments below invite some response. When I‚m not trying to tell 18-22 year-olds about the beauty of molecular orbital theory or why lab notes need to be written in pen, I spend my vacant hours as a volunteer firefighter and I have hazmat training at the technician level. So, WHENEVER there is any kind of call (fire, hazmat) at a „target hazard‰ such as an academic science building, the local fire department will send just about everything available to them because they have to assume the scenario could be the „worst-case scenario‰, and the worst-case scenario can be really bad. For that matter, when we get called to a „two car collision with multiple injuries‰ we are going to send an engine, two ambulances, a rescue vehicle with jaws, and just about all the personnel we have at hand∑ just in case. The collision might turn out to have been a fender-bender with no injuries, or perhaps we find there are two fatalities, four serious injuries, and one car is on fire and the other has trapped occupants. We are instantly short-staffed once on scene, and lives are at stake. Fire departments can‚t know, until they are on scene, what the situation is. We expect the worst, and hope for the best. So, perhaps our putative need for instant journalism leads to errors in reports, but please don‚t second-guess an over-response by the fire department, especially in hazmat instances. In addition to being prepared for the worst (even when the preliminary dispatch makes this seems very unlikely) there are rules that firefighters have to follow about how to respond (or „over-respond‰) that are partially driven by liability issues. Similarly EMTs sometimes „backboard‰ and immobilize a patient (to prevent C-spine injury) who has already been ambulatory for 20 minutes prior to our arrival. It‚s the rules. This feels pretty silly∑ but one time when I did this I later found out that the patient I had strapped in (almost apologetically) had indeed fractured a vertebra! No, it will not take 23 firefighters to neutralize a tiny spill. But it will surely take that many, and more, to handle the worst-case scenario that might have led to the fire alarm being pulled. Dispatchers try to get the best information possible when talking with a 911-caller, but sometimes the information is not accurate. In hundreds of responses over the years, I‚d guess that 98% of the time the situation was not as bad as it could have been. The other 2% were „memorable‰. Dave David C. Finster Professor, Department of Chemistry University Chemical Hygiene Officer Wittenberg University 937-327-6441 http://userpages.wittenberg.edu/dfinster/index.html ==From: Steve Bonnell Subject: RE: [DCHAS-L] Chemical Safety headlines from Google (24 articles) Date: October 26, 2011 3:40:16 PM EDT Sort of reminiscent of the Cincinnati FD's response to a HNO3 dump when a hose failed during transfer from an above-ground tank to a tanker truck. The fuming nitric acid did not respond to being diluted with water as they had expected. There is no reaction involving nitric acid at standard conditions that will go exothermic enough to melt copper∑but, it will put copious quantities of vapor into the air, enough to evacuate several hundred houses downwind if you dump water on it. As I recall, nitric acid reacting with baking soda is scarcely exothermic but, the copper piping would rapidly turn into copper nitrate on exposure to the, as of yet un-neutralized, acid. The effect might be characterized as 'melting' by a reporter who is untrained. ==From: ACTSNYC**At_Symbol_Here**cs.com Subject: Re: [DCHAS-L] 4 RE: [DCHAS-L] Chemical Safety headlines from Google (24 artic... Date: October 26, 2011 3:49:06 PM EDT To: dchas-l**At_Symbol_Here**med.cornell.edu Yes, but how much gas would you create with a total spill of 1000 mg HNO3 getting on a few copper tubes from compressed gas cylinders? And this would have been a non-issue last year when the TLV-TWA for HNO3 gas was 2 ppm and the TLV-TWA for NO2 was 3 ppm. But now you are right because there is a notice of intended change to lower the TLV-TWA for NO2 to 0.2 ppm. That only leaves the question of the small volume of the spill and how much contacted copper. I'm familiar with this because the artists in the printmaking labs are commonly hunkered over big open baths of somewhat more dilute nitric acid watching the tiny bubbles of nitrogen dioxide form on their copper plates and rise to the surface. Go figure. Monona ==From: Alan Hall Subject: RE: [DCHAS-L] 4 RE: [DCHAS-L] Chemical Safety headlines from Google (24 articles) Date: October 26, 2011 3:39:13 PM EDT Yes, oxides of nitrogen (NOx) such as NO2 can be nasty gases under certain exposure conditions (such is in Silo-Filler's/Unloader's Disease or in ice rinks where the Zamboni engine is so improperly tuned as to produce a lot of NOx rather than the usual CO). And having taught Advanced Hazmat Life Support (AHLS) for many years and once in the past dark ages when there was still hair been a volunteer firefighter and wore the turn-out gear and an SCBA, perhaps the on-site time was not at all unreasonable. But let's be a little realistic for this particular scenario. A 1-L bottle of nitric acid was dropped and broken, and so far no one seems to know the concentration, so there are missing data. The conversion factor for NO2 according to the latest NIOSH Pocket Guide is 1 ppm = 1.88 mg/m(3). Looking at various OEHLs for NO2, NIOSH REL: 1 ppm NIOSH IDLH: 20 ppm OSHA PEL: 5 ppm And we should probably consider the ACGIH TLV/TWA and more importantly the AIHA ERPG-1 values which I just don't have time to look up right now. At airborne concentrations of significance in a HAZMAT event, quite often there is a readily-perceptible reddish-orangish-brownish cloud visible. Great if you see it, you need SCBA to approach. Not great if you don't see it: the environment is not necessarily safe! And given 1 L of some (unknown) concentration of nitric acid interacting with some copper tubing, how really likely is it that a clinically significant amount of NO2 or other NOx were released? I'll leave this to the chemists in the group, but to a Medical Toxicologist it seems unlikely. Certainly NOx (including NO2) are worrisome because in quite high concentrations they can result in delayed onset of non-cardiogenic pulonary edema, ARDS, and even respiratory death. These "disaster scenarios" seen rather unlkely in the incident described. Why does it take 20+ firefighters about an hour to deal with this? Kinda like shooting a flea on an elephant's behind with a large-caliber elephant gun? Might kill the flea, but consider the cost and potential consequences! Maybe all but one or two were trainees from the local Fire Academy who needed some experience in responding? Perhaps the initial call to the FD exaggerated the possible significance of the incident? In any emergency call, you just plain don't know until your boots are on the ground (and even then it can take some time for scene assessment). Alan Alan H. Hall, M.D. Medical Toxicologist AHLS Verified Provider and Instructor ahalltoxic**At_Symbol_Here**msn.com
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