Date: Fri, 5 Mar 2010 10:41:36 -0800
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: bill parks <misterbill21225**At_Symbol_Here**YAHOO.COM>
Subject: Re: Emergency purge mode for fumehood
In-Reply-To: <B25C370F3F6ADF4D94FE33CE1698D1B10714675B**At_Symbol_Here**>

I believe the "Emergency Purge Mode Switch" works well for fumes, vapors, and some light mists, not so much for flammables that are combusting. The instruction manual/instructions/vendor/installer should have mentioned this. To put out active fire in a hood or the ductwork, a built-in Fire Suppression system needs to be installed. The purge fan only increases the air flow - which you have discovered.

More responses from the rest of the list to follow, I'm sure.

Bill Parks

**Providing sound Industrial Hygiene, Occupational Safety and Health, Environmental Health & IAQ, Environmental, and Laboratory support services and solutions for over 25 years**

--- On Fri, 3/5/10, Tan Khai Seng  wrote:

> From: Tan Khai Seng 
> Subject: [DCHAS-L] Emergency purge mode for fumehood
> To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
> Date: Friday, March 5, 2010, 10:36 AM
> Hi everyone 
> for some fumehood, especially the VAV fumehoods, they come
> with an emergency purge button which is supposed to increase
> the exhaust rate in the event of a spillage. 
> I have just encounter an incident where a distillation was
> wrongly set up, the set up went flying after 2 hours and
> toluene was spead all over the fumehood. The researcher
> instinctively close the sash fully and activate the
> emergency purge mode. by then, the toluene had ignited and
> the activation of the purge mode actually fanned the fire.
> the fire was big enough to melt the flexible duct connecting
> the fumehood to the exhaust duct. the researcher was able to
> contain the fire within the fumehood and extinguish it with
> the fire extinguisher.
> we are debating over the question of whether to activate or
> not to activate the emergency purge button.
> any advise?


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