Date: Sat, 31 Oct 2009 09:20:50 -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: Lindsey Kayman <kayman**At_Symbol_Here**UMDNJ.EDU>
Subject: Re: Roof top exhaust fan maintenance Policy
If the hoods are all ganged together helps reduce potential exposure
thanks to dilution.
There is also a special hazard if each hood has its own fan
and the fans are located in a penthouse with the stacks going through
to the roof. Leakage on the positive pressure side could result
in substantial exposures to people working in the penthouse.
Lindsey
>>> ACTSNYC**At_Symbol_Here**CS.COM 10/30/2009 12:36 PM >>>
Ideally, if they
are maintaining the fans and people are not using the hoods while they are
working, there should be no problem. I'd worry more about deposition
of contaminants in the fans and ducts which sometimes occurs.
But this is only true if the stacks and fans were properly
designed and engineered. Instead, what I see on the roofs of most
university science buildings are rain capped exhausts or exhausts that are
so low that the emissions will put workers at risk who are on the
roof. Hell, it's even worse than that--often the stuff is going
right into the air handling units for the general recirculating system for
the building.
If the building was built to the ACGIH Industrial
Ventilation standards and to local department of environmental protection
standards, those stacks would be tall enough or specially boosted to
exhaust only into moving air above the building. The height of the
stacks should not be left to architects (who want no protuberances above
the roof line) and engineers (who want to specify as much off the shelf
equipment as possible). Instead, the height should be determine by
standards and regulations.
If the stack heights are proper,
the workers on the roof will not be exposed to the emissions. If
they are, maybe a redesign is the way to go.
Monona Rossol
In a message dated 10/30/2009 11:49:21 AM Eastern
Daylight Time, stefan.w**At_Symbol_Here**UCONN.EDU writes:
In general,
maintenance staff working on rooftop fume hood exhaust equipment have
indicated their concerns about being on a roof, and possibly being exposed
to whatever is being vented.
In a more specific
laboratory situation, involving MOCVD (metal organic chemical vapor
deposition), we have a lock-out tag-out policy, due to the severity of the
toxic gases involved.
Questions:
Does anyone else have MOCVD labs,
and to what extent are controls in place for protection of workers on roof
tops?
Does anyone else employ a LOTO policy?
Are roof tops key-accessible only?
Thanks for the
feedback.
-Stefan Wawzyniecki, CIH, CHMM<
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University of Connecticut
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