Date: Tue, 4 Oct 2011 20:45:33 -0700
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Sender: DCHAS-L Discussion List <dchas-l**At_Symbol_Here**med.cornell.edu>
Subject: There is no "new" ANSI minimum hood flow rate
X-cc: Beatrice Barry
As the current chair of the ANSI-AIHA Z9.5 subcommittee, I am hoping to use 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 matter.
I received a report recently about "an especially large group (of interested parties) at the Labs 21 conference...and hearing people talking about "the new ANSI flow level" as though we had erased one number and wrotein another." For the record, I feel obliged to add something to the vacuumcreated 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 reportedly 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 CAV 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 wouldhave been a lot easier to control what filled this particular vacuum if weall 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 ANSIminimum 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 and sustainability IS not entirely outside the scope of this standard anymore. 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 volunteerto help make the next revision even better.
Steve Crooks, MS, CIH, CSP
Chair, ANSI/AIHA Z9.5 20##.
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