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From: kwe@buit13.bu.edu (Kent England)
Newsgroups: comp.dcom.lans
Subject: Re: Fire codes & cabling
Summary: It is complex
Message-ID: <65455@bu.edu.bu.edu>
Date: 3 Oct 90 15:22:49 GMT
References: <65129@bu.edu.bu.edu> <4277@husc6.harvard.edu> <1990Sep28.093731@mortal.enet.dec.com>
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Reply-To: kwe@bu.edu (Kent England)
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In article <1990Sep28.093731@mortal.enet.dec.com> 
 knight@mortal.enet.dec.com (Paul Knight) writes:

> [I said:]
>|> An example of environmental airspace is room space. 
>
>No No No!  You can use PVC in offices, rooms, etc.   There has been some 
>discussion of not allowing it for computer rooms, however.  I'm not sure
>of the status in computer rooms now.
>
	Environmental airspace is space where people work and breathe.
This refers to offices, labs, and hallways.  If you have open ceiling
labs with exposed cabling or open ceiling hallways with cable trays,
then your cables are in environmental airspace and are subject to low
smoke emission restrictions.  This applies in "room space" by any
interpretation of the term.

	It is true that cables that attach devices to the building
cabling system are not included in current codes.  This may change.  I
know that furniture is included in some fire codes, but, of course,
not in the electrical part of the spec.

	Computer rooms are very dangerous places to be in a fire.
Cables are usually not fire rated, and they are usually installed in
"plenum space" where ventilation would force toxic smoke out from
under the floor and into space where people breathe.  I expect
computer rooms to come under low smoke regulation at some future time.

>
>In NO CASE can you run cables through air ducts.
>
	Did I say that?  It is something you need to watch your
contractors for.

>Your best rule of thumb is to use CL2P for any behind-the-wall or 
>over-the-ceiling wiring.

	Except that someone may challenge that assumption and you
might save a lot of money doing it in other ways without losing fire
safety.

	I did not mention conduit.  Conduit, while expensive, is
useful in many situations.  For example, if you are using trunk
cabling that does not need to meet spec in exterior ducts, you can
bring it in from the street into your riser system in steel conduit,
providing good physical protection and compliance with fire codes.

	Another thing I did not mention is firestop integrity.  When
installing cable (low smoke or otherwise), you must be sure to
maintain the integrity of the firestops and firewalls designed into
your building.  We design our network closets with all four walls as
firestops, with double drywall from structural floor to structural
ceiling.  The entire riser system is one fat fire rated conduit.  We
don't need low-smoke compliance in our risers, but we do need to
maintain the firestops and that means capping all unused sleeves that
penetrate firewalls, and filling all used sleeves with a suitable
firestop material.

	This is especially important during retrofits.  You must not
punch big holes in firewalls- you should install sleeves with tight
seals around the outer perimeter and either caps or firestop in the
sleeves.  Especially important is firestopping vertical sleeves in
your riser.  Don't use slots.  They are easy to pull cable thru but
hard to firestop.

	In general, remember what the fire code designers are trying
to do:

	First, inhibit the spread of fire.

	Second, ensure a safe period during which people can safely
evacuate a burning building without injury or poisoning.

	Firestops help retard the spread of a fire.  Low smoke cabling
ensures that during the period before flashover (when anyone left in
the area would die anyway), people can escape without being burned or
poisoned by inhaling toxic emissions from burning cabling that is in
their environmental airspace.  You do not want to find yourself in the
position of contributing to the unnecessary deaths of people from
toxic fumes.

	And another thing: in retrofits, make sure that your
contractors don't block fire exits while working or leave ceiling
tiles misplaced during off hours.  These sorts of mistakes also
contribute to dangerous conditions during fires by disrupting airflows
and blocking egress.  It sometimes seems to me that every contractor
thinks that stairwells are the best places to store materials and
prepare construction materials.  Don't let them do it.  Far better to
disrupt the office space than to block the exits.  Again, you don't
want to find yourself responsible for unnecessary deaths or injury.

	I wish I could give you the cookbook on fire safety, but with
some practice and experience you should find a simple set of standard
procedures that will do the job.  Just remember that the fire rating
of the cable is but one part of fire safety as it related to low
voltage building cable distribution systems.

	I guess that is enough.  Who wants this soapbox next?  :-)

	--Kent