Wendy, if you can share, what evidence do you have of perchlorate contamination?
Also, have you considered contracting the service – ei ther high haz evaluation or full high haz removal? Perchlorate-contaminate d ductwork presents a number of tough problems – such as removing portions of a duct run without introducing friction or vibration to a contaminated site. The approach needs to guard against metal perchlorates built-up at duct joints, at individual screws, etc. I believe there are heat-imaging field device s that help visualize pre-detonation reaction – but that’s my fuz zy memory on that. This gets very expensive – perhaps the largest problem is properly identifying work that should not proceed without the hi ghly skilled help (and corresponding price tag).
In concept, every lab hood system can be considered perchlorate-contaminated, albeit at differing confidence levels. What I mean to say is that you frankly don’t know if some researcher ran hea ted perchloric up the hood a decade or two or three back, regardless of that ho od bearing the label “perchloric hood”. Servicing any lab hood syste m in a chemical lab building should not be done lightly. To an appreciable extent, you have residual risks you don’t get to fully eliminate in t he duct systems. But the more robustly you can build a case for the high haz price tag, the more likely purse strings will loosen for you in a given cas e.
Hope this helps,
Nicholas J. Tsiakals
Division of Research Safety
Chemical Safety Section
University of Illinois at Urbana-Champaign
(217) 244 - 0682
"If we don't train students in risk management and safe ty procedures, then we're not training them for employment in modern industry. If we want someone to turn up in a job and be productive, t hey can't do that if they're not safety aware." p>
-- Prof. Thomas Welton, Head, Department of Chemistry, Imperial College London --
We moved several perchloric acid hoods some years ago without incident. The city fire department was quite willing to standby at the scene. Wash down with plenty of water from the top down. Perchlorates like to build up at bends so go slow and wash well, particularly the fans. Do n't rely on the old-timers, the hoods were used with perchloric acid.
On Thu, Apr 15, 2010 at 1:38 PM, Wendy Campbell <wendycampbell**At_Symbol_Here**boisestate.edu a>> wrote:
We are in the process o f remodeling a building, which currently houses an old perchloric acid fume hood. I'm still tracking down how old it is, but I'm fairly sure it's at least 30 years of age. As part of the remodel, the perc hood is to be removed. There are several issues here.
1. No one remembers any hot perchloric acid work ever being performed in this hood (I'm still tracking down the recently retired folks to see what t hey know), and it has been either sealed shut or used as a regular chemical fum e hood over the past 10-15 years. I'm not sure whether trusting in peop le's memories over the course of the hood's life is the best policy.
2. The duct system is plumbed above the bench of the hood so that it washes a six foot run of ducting and the hood itself. The plumbing do es NOT extend any farther up the duct system, nor out onto the roof where it vents, which leads us to.........
3. The duct takes a turn approximately two feet above where it emerge s from the roof, and has approximately 3-4 feet of vertical run to the blower assembly.
The plan under consideration at the moment is to start on the roof and chec k each section for the presence of perchlorates, then spray the heck out of i t with water before removing just that section.
I'm hoping for some feedback regarding other people's experiences, suggesti ons for procedure / materials, and anything else the combined wisdom of these f ine groups can give us to perform this remodel safely and in a timely fashion. I know the contractors would like to start within the next couple of weeks.
Pictures of the rooftop portion of the hood's exhaust system have been post
to the AIHAH and Hazmat group sites on Yahoo, but I'm still working on how
share my Flickr account with folks - perhaps just contacting me off-list?
Thanks in advance,
Wendy Campbell, ASP
Occupational Health and Safety Officer
Environmental Health and Safety
Boise State University
1910 University Drive
Boise, Idaho 83725-1826
Office: (208) 426-3303
Fax: (208) 426-3343
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