For the kinds of tests that we have been talking about, I don't
believe that the Cone is used. It isn't identified in the UL 1950 standard
directly, or through other standards. I don't think (I'm sure somebody will
correct me here) that the Cone is even used during the NEBS testing, where
they are really starting a fire inside the equipment as part of the test.
The cone does get used when trying to determine the contents and effects of
smoke, particularly on other equipment, but not during normal testing.
Gary
-----Original Message-----
From: John Juhasz [SMTP:[email protected]]
Sent: Thursday, April 22, 1999 6:51 AM
To: 'JENKINS, JEFF'; John Juhasz; 'Rich Nute'
Cc: '[email protected]'
Subject: RE: Excessive smoke
The heart of the Fire Resistance test is the 'Cone Calorimeter'
developed by
Vytenis Babrauskas, Ph.D. (the Ph.D. is in Fire Science). The cone
Calorimeter is located within a 'hood' above the test sample. UL,
ASTM,
Bellcore, Western Fire Center, and additional labs, utilize this
device. The
smoke is sampled as it passes the cone calorimeter while being
exhausted out
of the test chamber.
I don't know the details, but I do know that the duct is a given
diameter at
that point.
For more information on the calorimeter see the following link (then
click
on 'facilities'. There is a link for detailed technical info).
http://www.westernfire.com/
Additionally, Bob Backstrom of UL's Northbrook, Ill. office, is a
fire
safety expert and was involved with the development of the standards
utilized by UL and Bellcore. He could also be of help.
John A. Juhasz
Product Qualification &
Compliance Engr.
Fiber Options, Inc.
80 Orville Dr. Suite 102
Bohemia, NY 11716 USA
Tel: 516-567-8320 ext. 324
Fax: 516-567-8322
-----Original Message-----
From: JENKINS, JEFF [mailto:[email protected]]
Sent: Thursday, April 22, 1999 9:37 AM
To: 'John Juhasz'; 'Rich Nute'; JENKINS, JEFF
Cc: '[email protected]'
Subject: RE: Excessive smoke
John, is the smoke measured in a room of a specified volume? That
is to
say, how is compliance with the 28% Oxygen Rating Index determined?
Jeff
-----Original Message-----
From: John Juhasz [mailto:[email protected]]
Sent: Thursday, April 22, 1999 6:38 AM
To: 'Rich Nute'; '[email protected]'
Cc: '[email protected]'
Subject: RE: Excessive smoke
Good Answer (with respect to the standards noted below).
However, I would like to expand on this discussion, if I may, with
regards
to
telecom equipment in a CO (Central Office) environment and meeting
Bellcore
specifications (realize that typically equipment that will go into a
CO
environment will also need to meet UL 19503rd ed.).
In the case of Bellcore NEBS GR-63, the content of smoke is measured
with
regard to
'Oxygen rating index' (should be 28% or greater) during the Fire
Resistance
testing. The previous version of the specification (TR-NWT-000063)
specifically measured all the content of the smoke to determine
smoke
corrosivity.
Although the current standard (GR-63) is relaxed, the RBOCs
(Regional Bell
Operating Companies - becoming less numerous of late) reserve the
right to
view the video tape of the fire test when considering a product, and
if they
feel that the product is producing too much smoke (regardless of the
oxygen
index) they become concerned.
They're concerned about bringing down a central office to 'clean'
the
surrounding equipment from the corrosive elements of the smoke.
So those of you who will also need to meet the Bellcore NEBS
requirements
(telecom equip to be located in a CO) in addition to UL1950 3rd Ed.,
this
will be a concern.
John A. Juhasz
Product Qualification &
Compliance Engr.
Fiber Options, Inc.
80 Orville Dr. Suite 102
Bohemia, NY 11716 USA
Tel: 516-567-8320 ext. 324
Fax: 516-567-8322
-----Original Message-----
From: Rich Nute [mailto:[email protected]]
Sent: Wednesday, April 21, 1999 2:30 PM
To: [email protected]
Cc: [email protected]
Subject: Re: Excessive smoke
Hi Jeff:
> If a component abnormal test generates excessive and sustained
smoke
> (several minutes), but does'nt breach reinforced or double
insulation,
nor
> emit flame from the enclosure, is it considered a failure?
Intuitively,
it
> seems like it would be, because of toxicity, but I have been
unable to
find
> anything in the safety standards to support this. I have
checked EN
60950,
> EN 50178, UL 1012, and CSA C22.2 No. 107.1.
For the purposes of product safety and compliance with safety
standards, smoke is a "permitted" emission during fault testing.
The safety issue is whether a safeguard is damaged or breached
due to the heat which produced the smoke. If insulation is not
damaged (as per the hi-pot test), and excessive heat or flame
does not breach the enclosure (as per the cheesecloth test),
then the product is considered acceptable for the purposes of
product safety.
Typically, product safety standards do not address the toxicity
of smoke. This is because all smoke contains toxic materials.
The only solution to smoke toxicity is to eliminate smoke, which
means eliminating all overheating situations. Which is nearly
impossible.
However, any smoke from a product is likely create fear and
anxiety in the mind of the user and nearby persons. Any smoke
in a clean room will likely be cause for scrapping all stock in
the clean room.
While smoke always contains toxic materials (e.g., carbon monoxide),
the concentration of the smoke (toxic material) in the volume of
the room together with the room ventilation determines whether or
not inhalation of the smoke is likely to cause an injury. If the
volume of smoke is small compared to the volume of the room, then
it is likely the concentration of toxic material will be below the
TLV (threshold limit value) for that material.
So, it is a good idea (for the satisfaction of your customers) to
eliminate or reduce any significant smoke emissions that might
occur during fault testing.
Best regards,
Rich
-------------------------------------------------------------
Richard Nute Product Safety Engineer
Hewlett-Packard Company Product Regulations Group
AiO Division Tel : +1 619 655 3329
Effective 6/12/99: +1 858 655 3329
16399 West Bernardo Drive FAX : +1 619 655 4979
Effective 6/12/99: +1 858 655 4979
San Diego, California 92127 e-mail: [email protected]
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