From: 8524828hau**At_Symbol_Here**COMCAST.NET
Subject: Re: [DCHAS-L] perchloric acid fume hoods
Date: March 4, 2013 10:00:51 AM EST
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: <B45065CA11547E4BB3E9D911C1BEAE5A0A44D1EB**At_Symbol_Here**>

Hello all who have been interested in the dialog about hoods and down-stream duct work when perchloric acid has been vaporized by heating:

I had no intention of participating in the dialog, but find I am obligated to do so because I have seen no explicit mention of the shock-sensitive explosive metal perchlorate salts that can accumulate in down stream duct work that is not subjected to counterflowing water during heating of perchloric acid.  Shocks introduced by mechanical disassembly of ducts and their connection to hoods have the potential for causing at least minor localized explosions -- as explained to me by a well-qualified industrial hygienist.  

As an extra precaution, polymeric (PVC??) ductwork and fasteners are installed for hoods that will be used for heating perchloric acid, thus eliminating the liklihood for accumulation of shock-sensitive metal perchlorates.  The ductwork is dedicated to serving the perchloric acid hood, e.g., is not part of a manifold of metallic exhaust pathways. 

A quick search revealed an informative article about discovery and remediation of perchlorate contaminated ductwork at Oak Ridge National Laboratory (ORNL) at:

An informative "report" about the formation of explosive perchlorates on hood walls is available at

Observe the importance of the presence of water to decrease (or eliminate) the likelihood of shock sensitive explosions. 

David Haugen
Retired in Illinois

From: "Ellen M Sweet" <ems325**At_Symbol_Here**CORNELL.EDU>
Sent: Monday, March 4, 2013 7:45:41 AM
Subject: Re: [DCHAS-L] perchloric acid fume hoods

Hi Mary,

We've had some experience in this office. Below is a link for a test method for contamination inside of the hood. I recently used this on a standard hood for a lab group that had 70% perchoric acid in storage from the previous lab occupants. So the manager couldn't tell me how the acid was used. I didn't want to go to the extent and expense of having a company come in to test the ductwork if the acid wasn't ever heated


This aside, you should have any perchloric acid hood be tested by a company that does that. I can't suggest any vendors for you, specifically, as you are on the other side of the country. But, sometimes the same companies that do chemical stabilizations (high-haz team) and remediation do this type of testing and decon too. I'd suggest asking your EHS folks that deal with hazwaste removal for the chemical waste hauler your company is using. They should be able to give you the name of a company or two that provide perchlorate testing and decon in your area.

Good luck,


Ellen Sweet

Lab Ventilation Specialist

Cornell University Environmental Health and Safety

office: (607) 254-8644

cell: (315) 730-8896



From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of Lanza, Mary Beth
Sent: Friday, March 01, 2013 7:37 PM
Subject: [DCHAS-L] perchloric acid fume hoods


Does anyone have experience with the removal of perchloric acid hoods from a lab?  Any information on the subject and references to resources capable of performing this task would be greatly appreciated.  I do realize there is a special procedure and tremendous cost associated with this, but I wanted to get a better idea of specifically what is involved.

Thank you.

Mary Beth Lanza
Scientist - Infrared Spectroscopy
Weyerhaeuser Analytical Chemistry
WTC Chemical Hygiene Officer
(253) 924-6013 (desk)
(253) 924-6290 (lab)
(253) 924-6654 (fax)

Need to request testing services?  Want to know more about Analytical Chemistry & Microstructure?  Visit us at:





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