Date: Thu, 6 Oct 2011 14:29:37 +0000
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Sender: DCHAS-L Discussion List <dchas-l**At_Symbol_Here**>
From: Russell Vernon <russell.vernon**At_Symbol_Here**UCR.EDU>
Subject: Re: There is no "new" ANSI minimum hood flow rate
X-cc: "DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU"
In-Reply-To: <001901cc83b2$12d0e880$3872b980$**At_Symbol_Here**net>

Hi Bruce,
I had to comment on you term "no potential for exposure".
There are materials and operations for which even a properly functioning fume hood will not achieve "no exposure"

I would love to find criteria that could be reasonably applied to help the prudent person decide when to work in a lab fume hood and when to work in a glove box...

Anyone know of one?


Sent from my iPhone

On Oct 6, 2011, at 5:06 AM, "Bruce Van Scoy"  wrote:

Before I opt to purchase yet another standard, would you please specify the
benefit of this standard as compared to installed/as-built performance
testing, e.g., ASHRAE Standard 110-1995 "Method of Testing Performance of
Laboratory Fume Hoods" using SF6 at 4LPM?  If I can effectively prove that
we are controlling all exposures at a lesser flow rate, is that acceptable
under the 25 cfm/ft2 minimum found within the ANSI standard?  I really don't
care which standard is applied as long as I can defend in court that
employees have no potential for exposure.  Is that still acceptable?
Please advise, thank you.

-----Original Message-----
From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of
Mary Ellen A Scott
Sent: Wednesday, October 05, 2011 11:13 AM
Subject: Re: [DCHAS-L] There is no "new" ANSI minimum hood flow rate

Is there any note on a flow monitor for a fume hood being required
now, even on older fume hoods?

On Tue, Oct 4, 2011 at 11:45 PM,   wrote:
As the current chair of the ANSI-AIHA Z9.5 subcommittee, I am hoping to
this forum to counter some erroneous information that has been circulating
about the forthcoming standard. Whether the information was outright or
egregiously misleading or just audience misinterpretation doesn't really
I received a report recently about "an especially large group (of
parties) at the Labs 21 conference...and hearing people talking about "the
new ANSI flow level" as though we had erased one number and wrote in
another." For the record, I feel obliged to add something to the vacuum
created by the slow consensus publishing process.

The standard revision replaces the 25 cfm/ft2 of work surface minimum flow
rate with performance oriented language (which may more cautiously assign
minimum flows for floor-mounted hoods with much larger interior volumes).
The standard revision refers to studies and European experience where flow
rates less than what would have been possible at 25 cfm/ft2 have
been used (thus far) with success.
The standard revision is steadfast in the actual requirements section (the
left-hand column) and offers no room for placing energy conservation ahead
of safety. Without copying verbatim and getting AIHA upset with me, let me
just say that the bottom line is this; designers and owners must choose
hood flow rates and VAV hood minimum flow rates which prevent hazardous
concentrations of contaminants in the laboratory fume hood. An extensive
right-hand column goes into some detail describing and defining potential
hazardous concentrations.

I do regret that the revised standard hasn't been published yet. As we all
know, (information) vacuums get filled. It would have been a lot easier to
control what filled this particular vacuum if we all could be reading and
interpreting the same text. Unfortunately, publication appears to be out a
few more months.

In the mean time, if you hear someone mention the "new ANSI minimum hood
flow rate," politely correct them and assure them that in some cases,
applying the revised standard could in fact raise the minimum (from 25
cfm/ft2). It will be fair to say as well that environmental performance
sustainability IS not entirely outside the scope of this standard any
The subcommittee hopes that where appropriate, an equally safe but smaller
carbon footprint may now be possible so long as safety isn't compromised.

I encourage those with a role in laboratory ventilation management to
purchase the standard once it's finally ready and volunteer to help make
next revision even better.

Thank you,
Steve Crooks, MS, CIH, CSP
Chair, ANSI/AIHA Z9.5 20##.

Mary Ellen Scott, PhD.
Safety Specialist II
Case Western Reserve University
EHS - Environmental Health and Safety
Service Building 1st Floor Rm 113
2220 Circle Dr.
Cleveland, OH 44106-7227
216-368-2236 (Fax)
"There is no science without fancy and no art without fact" - Vladimir
Nabokov (1899-1977)

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.