We're right back to the starting point. No quantitative measurement, (and
I'm not sure that if we think about it real hard that we want to much
oversight here). You're note below indicates one quantitative metric ,
oxygen index, and then immediately points out that it may get thrown out
because of a qualitative assessment; the RBOC's reserve the right to view
...... and if they FEEL its that.... This right is based on, if you'll
pardon me, smoke and mirrors.
Rich makes some very good points about the only metrics really available,
dielectric withstand afterwards etc, and I have successfully argued them to
get product acceptance. But the bottom line is that we have to use a little
thought before deploying any product. You may be able to get the safety
label but does that mean you ship it. Again, Rich's comments on clean rooms,
or other secondary hazards, comes to point. You might get it past UL, but
you have a whole other problem when the customer comes calling because of
the failure.
Excessive smoke really has to be determined by the designer for the use and
application of the product. The various agencies may have a minimum
requirement but in my opinion you need to have either accepted or rejected
the smoke levels base on you own requirements and then proceed. If the
agencies are concerned hold them to the standards, as indefinite as they may
be, or possible rejecting the product even before it gets that far if you
application requirements are more stringent than the agencies. If I were
building a product for the growing number of environmentally sensitive
folks, any smoke would be too much, regardless of the standards. If I were
building it for a development lab I might not be quite so stringent. Having
let the smoke out of several transistors I don't think a little more is of
critical nature.
-----Original Message-----
From: John Juhasz [SMTP:jjuh...@fiberoptions.com]
Sent: Thursday, April 22, 1999 5:38 AM
To: 'Rich Nute'; 'jeff.jenk...@aei.com'
Cc: 'emc-p...@ieee.org'
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:ri...@sdd.hp.com]
Sent: Wednesday, April 21, 1999 2:30 PM
To: jeff.jenk...@aei.com
Cc: emc-p...@ieee.org
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: ri...@sdd.hp.com
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