Date: Sun, 29 Aug 2010 10:52:16 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Steve Crooks <crookssm**At_Symbol_Here**MINDSPRING.COM>
Subject: Re: Hoods failing annual calibration
In-Reply-To: <2037849344.4615.1283020392162.JavaMail.root**At_Symbol_Here**>

To those interested in this thread,

I too have encountered this question from a metrology person and recall at the time thinking how great it was that they were making such an extension from their FDA world.=C2=A0 Confronted with our related experiences with known post-exposure reconstruction events, we set the bar pretty low though as far as expecting a black or white answer.=C2=A0 And although we concluded about as Don has described, the exercise drew some useful attention to exposure control devices and how we trained folks in their selection, use, and inspection.=C2=A0 =C2=A0=C2=A0

On the selection front-end, we were reminded that fume hoods are not appropriate control devices for MANY substances (or at least without adding additional layers of protection.)=C2=A0 Our BEST hoods could knowingly leak a tracer gas (during a one-time commissioning test) into the breathing-zone of a stationary mannequin and would be ok so long as concentrations were below 0.1 ppm.=C2=A0 =C2=A0The "impact assessment=" question was placed with the research staff and began being used in training.=C2=A0 Are you using your hood to contain substances to which you=E2=80=99d be ok in the event that it periodically does NOT contain as well possible? =C2=A0If yes, swell.=C2=A0 If no, better do more work.=C2=A0 I later had an opportunity to help a researcher with a set-up involving H2Se gas.=C2=A0 The hood by itself was a poor choice as a control device so we made certain that the primary containment was the apparatus/rig itself with the hood offering ventilation only should a failure in that system occur.=C2=A0 Both pressure and chemical detection were also appropriately placed and designed to stop gas flow and alarm in the event of failure.

Daily use (and pre-use inspections) relative to our annual inspection program also gained some needed attention.=C2=A0 We used the comparison with other inspection programs with some hopeful impact.=C2=A0 The higher the risk or demand on the system and the likely result of a major safety system component failure, the more rigorous the inspection program should be (not just the annual one!)=C2=A0 Our personal vehicles for the most part with tires and brakes being important safety components have apparently come to provide acceptable risk with a mere annual inspection.=C2=A0 Although most vehicle safety experts would argue that we should do more ourselves, most of us don=E2=80=99t and we get by. =C2=A0Failure is immediately recognized though and dealt with (or not).=C2=A0=C2=A0 Fly in an airplane lately or know much about pre-flight inspections?=C2=A0 =C2=A0The point that we used and incorporated into training was something to the following affect.=C2=A0 Someone performs an ANNUAL CHECK to see if on the particular day and time of the test, your device is working "ok.="=C2=A0 While they use their results to imply a little about overall life-cycle performance and reliability, don=E2=80=99t presume that they infer a single thing from their test about YOUR safety with your particular use of the device.=C2=A0 Using your device to protect you from something insidious or with consequence? Your BEFORE USE inspection should be fitting.

Our dilemma grew a bit further as the exercise led to a series of ventilation device "what if failure=" scenarios and a particular concern being our vented balance enclosures - which had relied on a single HEPA filter (tested annually for integrity) before discharge back to the lab environment.=C2=A0 =C2=A0That=E2=80=99s another story but I still remember Mr. McCray (the metrologist) and hope he=E2=80=99s doing well.

Steve Crooks, MS, CIH, CSP


People, Property & Environmental Protection, Inc.

12 Reynard Place

Hillsborough, NC 27278


The views above do not necessarily reflect those of the ANSI/AIHA Z9.5 Laboratory Ventilation subcommittee of which I am also affiliated.

From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**] On Behalf Of Don Abramowitz
Sent: Saturday, August 28, 2010 2:33 PM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: Re: [DCHAS-L] Hoods failing annual calibration


You raise an interesting question, and thus far, replies have focused on restoring the hood to its performance criteria.  Seems you are asking more about whether and how one would evaluate the potential exposures to hood users who may have been inadvertently exposed to chemicals as a result of  having been operating a hood outside of its intended performance specs.

Seems there's an ethical component here about disclosure to users, and a technical question of assessing the potential exposures that may have occurred.  Both are difficult questions, and they require a lot of specific information about the particular circumstances involved.  

It would be difficult to correlate face velocity with exposure.  A 40% drop in face velocity does not mean 40% more exposure.  You'd probably need to do some sort of simulation to attempt to model the exposures. 

It's also important to consider what materials were handled in the hood.  If you were working with relatively low-toxicity-but-irritating or odorous materials (something like acetic acid comes to mind), and no one noticed any effects or odors, you might conclude there was little or no impact.   At the other end of the spectrum, biological monitoring and/or medical evaluation/surveillance could be indicated for highly toxic substances that tend to bio-accumulate.  Chances are your particular circumstances fall somewhere in between, and all you can do is try make thoughtful decisions based on the information and individuals involved. 

            & nbsp;                              Don

Donald Abramowitz
Environmental Health & Safety Officer
Bryn Mawr College
Bryn Mawr, PA

I work in a GMP laboratory in the medical device industry.  A member of our metrology team questioned me today as to what we would do in event one of our chemical fume hoods did not meet one or more of its annual qualification events, for example if the hood did not meet its face velocity requirement during the annual test.  We do have monitors on our hoods, but occasionally they have been found to be faulty.


According to our work instructions, any "instrument=" which does not meet any of its qualification events must have an impact assessment done.  Usually this relates to the impact the failure may have had on the results of tests that were done using the instrument.  But in this case we would be talking about a safety impact assessment rather than focusing on the results of tests.  The metrology member also mentioned to me that we should, according to our work instruction, have a usage log for each hood so that a proper impact assessment could be done. 


My thoughts are this:

I would not call a chemical fume hood an "instrument=" and therefore would not consider it subject to the previously mentioned work instruction

I have never heard of any facility having a usage logbook for chemical fume hoods


BUT=E2=80=A6 the question I really want to ask the group is this:  in the event a hood fails any of its annual calibration events, what do you do?   Do you speak to people who have been using the hood, prepare an impact assessment, etc.?



Pat Peifer

Health, Safety and Training Team Leader

The contents of this message are confidential and may be privileged. If you have received this message in error, please permanently delete it, along with any files that may be attached to this message, without reading, printing, copying, forwarding or otherwise distributing it. Please notify the sender of the error immediately so that we can prevent it from happening again.

Previous post   |  Top of Page   |   Next post

The content of this page reflects the personal opinion(s) of the author(s) only, not the American Chemical Society, ILPI, Safety Emporium, or any other party. Use of any information on this page is at the reader's own risk. Unauthorized reproduction of these materials is prohibited. Send questions/comments about the archive to
The maintenance and hosting of the DCHAS-L archive is provided through the generous support of Safety Emporium.