Hi Cynthia,

We have had two hood fires in recent years ignited by hot plates. In both c
ases this was due to explosive atmospheres inside the hood and I suppose th
at could be considered an "ambient" explosive atmosphere inside the hood.

In one case the worker was decanting isobutanol in a six foot hood with an 
unused, but plugged in, hot plate at the other end. The vapor flashed from 
the other side of the hood. 

In another case an unattended experiment flashed and triggered a sprinkler 
that flooded the lab and the lab below consequently ruining about $500,000 
in laser equipment.

Thankfully no one was injured in either case. I'd be happy to send pictures
.

Good question.

Chris

-----Original Message-----
From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**LIST.UVM.EDU] On Behalf Of cr
unkel**At_Symbol_Here**EMAIL.ARIZONA.EDU
Sent: Monday, April 27, 2009 9:59 PM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: [DCHAS-L] Explosive proof hot plate in a hood?

Interesting Question:

I am working on an issue about a "so-called' requirement for an explosive p
roof
hot plate installed in a hood.  The flammables used in the hood are no
different than any I have seen anywhere, in other words, they do not use la
rge
volumes or extremely flammable solvents.  What I cannot wrap my head around
 is
that my understanding of the use of explosive proof equipment is for ambien
t
explosive atmospheres.  Why should a hood with ventilation have an explosiv
e
proof hot plate requirement?

I appreciate any feedback or fire codes which would make this a requirement
.

Cynthia Runkel
Chemical Hygeine Officer