I agree with Ted, John, and Scott.
Cotton doesn't self-ignite from heat alone unless the heat
is applied quite quickly, before the cotton chars. In many
cases, ignition of cotton requires a flame. Charred cotton
doesn't burn.
The "Handbook of Physical Testing" gives cotton ignition
temperature as 475 C and the flash point as 361 C. See:
http://books.google.com/books?id=qa-I8QAOUL8C&pg=PA406&lpg=PA406&dq=cotton+ignition+temperature&source=bl&ots=FkF8ymi9GN&sig=FOeW52-9l7vA_PRdCjzbgkQZHRE&hl=en&sa=X&ei=M5U_UcnaHtKmqwHV_YCIDg&ved=0CFQQ6AEwAw#v=onepage&q=cotton%20ignition%20temperature&f=false
Flame-ignition temperature is about 200-250 C.
The notebook computer was on a pile of clothes, leading
one to hypothesize that the vents were blocked, thus
allowing the notebook temperature to rise to an abnormal
temperature. In addition, clothing is a good thermal
insulator, thus contributing to temperature rise.
Notebook batteries tend to be sensitive to higher
temperatures.
Notebook computer batteries have a reputation for internal
failures which cause overheating. My guess would be a
battery failure, leading to heating sufficient to ignite
the surrounding clothing.
Rich
On 3/12/2013 1:05 PM, Aldous, Scott wrote:
I don’t believe it. Yes, a notebook computer will get hot with the
vents blocked. Will it generate enough heat to ignite clothing it is
resting on? I highly doubt it. According to this website:
http://www.tcforensic.com.au/docs/article10.html
Cotton ignites at 250 degrees C (for some reason it’s in the table for
plastics). Even hay doesn’t ignite until it reaches 172 degrees C,
according to the same site. Notebook computers will not get that hot
even with all vents blocked. Thanks to the magic of Google, I happened
to find a CB report online for a notebook computer. I won’t link to it
just in case it’s not supposed to be public, but it got several
blocked vent tests (CB report issued by UL). It ran for several hours
for each test in ambients between 28 C and 29 C. The hottest
temperature recorded inside the computer, according to the report, was
81 C. Cheesecloth was not charred or ignited for any of the tests. It
was a relatively low power computer (the AC adapters it can use are
rated 65W out), but there is a long way to go from 81 C to 250 C.
There had to have been some additional type of fault there, as has
been suggested by John and Ted.
*Scott Aldous***
Compliance Manager/Engineering Lab Manager
AE Solar Energy
+1.970.492.2065 Direct
+1.970.407.5872 Fax
+1.541.312.3832 Main
scott.ald...@aei.com
1625 Sharp Point Drive
Fort Collins, CO 80525
www.advanced-energy.com/solarenergy
<http://www.advanced-energy.com/solarenergy>
*From:*emc-p...@ieee.org [mailto:emc-p...@ieee.org] *On Behalf Of *IBM Ken
*Sent:* Tuesday, March 12, 2013 1:13 PM
*To:* EMC-PSTC (E-mail)
*Subject:* Re: laptop -> house fire
"/P.E.I. deputy fire marshal Robert Arsenault demonstrates how vents
on a laptop computer can be blocked when it is sitting on a pile of
clothes. (CBC)/"
Why did he pick that brand of laptop to demonstrate with? XD
Does anyone have more information on this incident?
On Tue, Mar 12, 2013 at 2:49 PM, Brian Oconnell
<oconne...@tamuracorp.com <mailto:oconne...@tamuracorp.com>> wrote:
Blocked vent test anyone? Forseeable misuse? I like my computers well
done.
<www.cbc.ca/news/canada/prince-edward-island/story/2013/03/06/pei-laptop-hou
se-fire-computer-584.html
<http://www.cbc.ca/news/canada/prince-edward-island/story/2013/03/06/pei-laptop-house-fire-computer-584.html>>
-
----------------------------------------------------------------
This message is from the IEEE Product Safety Engineering Society emc-pstc discussion
list. To post a message to the list, send your e-mail to <emc-p...@ieee.org>
All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html
Attachments are not permitted but the IEEE PSES Online Communities site at
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used
formats), large files, etc.
Website: http://www.ieee-pses.org/
Instructions: http://listserv.ieee.org/request/user-guide.html
List rules: http://www.ieee-pses.org/listrules.html
For help, send mail to the list administrators:
Scott Douglas <emcp...@radiusnorth.net>
Mike Cantwell <mcantw...@ieee.org>
For policy questions, send mail to:
Jim Bacher: <j.bac...@ieee.org>
David Heald: <dhe...@gmail.com>
