This article deals with abandoned,
low-voltage communications cabling in building structures, and
the serious fire hazard concerns that prompted the 2002 National
Electrical Code to require the removal of abandoned cable.
The article was written with the goal of encouraging
electrical inspectors and other AHJs to enforce code
compliance.
In just the past 12 months numerous
training and educational seminars have been held by industry
trade organizations. Several major safety companies, riser
management firms and responsible contractors now offer
solutions for the removal of abandoned cable. Building owners,
property managers, and the like, are being encouraged to take
action in advance of compliance inspections to assess and put
in place a removal plan for abandoned cables. Electrical
inspectors also need to be brought up to speed.
Figure
1. Total installed plenum cable in the U.S.
The
Problem
During the early to mid-70s, businesses and other
organizations relied mainly on the telephone, perhaps
augmented with fax and teletype capability, to round out their
communications network. How the world has changed! The modern
business environment has been completely re-engineered by the
sharp and dramatic rise of ever-faster computer networks.
These networks not only move voice and data but are essential
to other building communications systems, such as
environmental monitoring, security, fire, and new powered
Ethernet devices. Each new generation of these systems relies
on large amounts of high performance low-voltage cabling to
operate reliably. However, as new higher performance cabling
is installed, rarely is the old cable plant removed. This
practice has resulted in layer upon layer of a mix of
abandoned low-voltage communications cables imbedded in the
concealed spaces of our commercial and public occupancies.
This huge accumulation of abandoned cable presents a serious,
hidden fire hazard to building owners, property managers and
tenants.
Abandoned cable presents several problems.
The large volume of accumulated cable not in use may prevent
the installation of new cabling because of completely
overfilled cable conduit pathways and spaces. Abandoned cable
also may severely restrict airflow in ceiling cavity plenums.
For these reasons, its removal may become a practical
necessity. In fact, this is often done. During a major
renovation when the building floor is gutted wall-to-wall, all
low-voltage network and communications cable is removed.
However, the most serious problem from
abandoned cables being allowed to remain in the structure is
their potential to both fuel and spread a very large, very hot
fire in concealed spaces, in the event of a building fire.
Also large amounts of smoke are generated making the fire
extremely difficult to find and fight. Over the years many
types of cable made from a variety of materials have been
installed, including 25 pair PVC telephone cable and IBM type
cable. The fire spread problem is further exacerbated when
firestopped penetrations are disrupted and are not adequately
replaced or protected when new cabling is installed in the
same pathways as the old.
Over half the weight of today’s typical 4
pair UTP (unshielded Twisted Pair) cable is comprised of
plastic insulation and jacketing materials. For example, the
installation of 100,000 feet of typical 4 pair UTP data cable
places approximately 1200–1500 lbs. of exposed plastic
materials in concealed spaces, when installed outside of
conduit as permitted by the NEC. An average, large
commercial office building can contain tens of thousands of
pounds of plastic materials as part of the in-use cable
infrastructure. Some of these plastic materials are engineered
to resist high heat, flame spread and smoke generation, while
others are not. Now add one or two layers of abandoned cable
and even more, perhaps orders of magnitude more, plastic
material is imbedded in the structure adding to potential fuel
load depending on materials used. Compared to power cable,
most of the combustibles in concealed spaces come from
communications cabling. It’s easy to see why the
combustibility or fuel load of remaining abandoned cable
materials is so critical, and why abandoned cable should be
removed.
Figure
2. Potential
heat of cabling materials
Figure
3. Simulation
of full-scale plenum fire
NFPA
Codes and Standards
Several devastating and tragic fires during the mid-to-late
70s, such as the MGM Grand in Las Vegas and the 1979 World
Trade Center fire in New York, gave rise to new provisions in
the NEC which required that new low-voltage cables
installed in buildings be listed as to their flame spread and
smoke generation characteristics. For example, only CMP type
communications cables are permitted in ceiling cavity and
raised floor plenum spaces. While this has been a major step
forward in improving fire safety, the problem is still with us
… and we can do better.
According to the NFPA, there are, on
average, 5800 fires in office buildings of six stories or more
every year—2.5 fires every day! In recent years several of
these office building fires, such as the 1996 Rockefeller
Center fire in New York and the One Meridian Plaza fire in
Philadelphia in 1991, along with many others, dramatically
displayed the potential hazard from low-voltage communications
cables, both abandoned and in use.
It should be noted that NFPA statistics and
fire investigation reports do not explicitly attempt to target
the role of communications cables in the spread of these
fires. However, after studying the fire investigation reports,
it is very clear to this author that we can construct a basic,
empirical understanding of the mechanism of fire spread in
many of these fires where cabling was involved. The ignition
source for many building fires is electrical in nature, from
overheating and electrical shorts. This clearly does not occur
with low-voltage cabling, as there is insufficient energy to
cause ignition of combustibles. However, since bundled
communication cables are typically installed in the same
risers and pathways near or adjacent to power cables, the
large amounts of low-voltage cabling are quickly exposed to
the fire. As shown above, some of the materials used in these
cables can behave as a solid fuel, spreading the fire
vertically in the risers and horizontally across ceiling
cavity plenums.
With the publication of the 2002 NEC,
the NFPA finally took long overdue action and addressed the
problem. The buildup and accumulation of combustibles from
abandoned cable mandated action and code compliance to help
alleviate and mediate the significant increase in occupancy
fuel loads. Other NFPA codes and standards followed suit and
took action on the growing concern over fuel load by
correlating with the NEC and issuing similar provisions
for the removal of abandoned cable. But actual enforcement of
cable removal can be problematic, particularly in buildings
when permits are pulled and business operations continue
during new cable installation projects. There may be
subjective judgment calls inspectors will need to make
concerning what is considered "accessible," and
whether cable "tagged for future use" is in fact
accurate or is it a ploy to take advantage of a loophole in
the Code.
As of this writing the NFPA 90A committee
responsible for the 2005 NFPA 90A Standard for Air
Conditioning and Ventilation Systems is considering even
broader reform to address the cable fuel load issue for both
abandoned and new cables added to buildings. NFPA 90A has
jurisdiction over the flame spread and smoke requirements for
materials (cable) exposed to the air flow in ceiling cavity
and raised floor plenums, while the NEC has
jurisdiction over the installation of those cables and wiring
methods. Ideally these two important documents should
correlate, and in the case of removing abandoned cable, they
do.
For years, 90A allowed the installation of
plenum approved listed CMP cable. However, this cable type was
allowed as an exception to the primary 90A requirement of
"limited combustible" for all materials exposed to
the airflow. It comes as a surprise to many that CMP cable,
while a decided improvement in reducing flame spread and smoke
in ceiling cavity and raised floor plenums, is in fact
combustible and can generate up to 17 times more smoke than
the maximum allowed by the limited combustible requirement in
90A. What this means for code officials and for contractors
who install cabling systems is that codes and cable types will
have to be examined more carefully to determine what cables
are, in fact, code-compliant and permitted to be installed in
the first place.
The 2005 NEC contains a fine print
note (FPN) that refers users to NFPA 13, Standard for the
Installation of Sprinkler Systems "for requirements
for sprinklers in concealed spaces containing exposed
combustibles." Under current NFPA definitions, exposed
CMP cables are combustible and have been assumed to be
code-compliant for all concealed building spaces. That may not
be true. NFPA 13 does not require that buildings be
sprinklered. However, when buildings are sprinklered under
NFPA 13, sprinklers are required in certain concealed spaces,
such as ceiling cavity plenums, when unprotected combustible
materials are present. The NFPA 13 Handbook on Automatic
Sprinkler Systems provides commentary and guidance on what
are considered "combustible materials." In
addressing the requirement for sprinklers in concealed spaces,
the Handbook states that these spaces "… can
contain combustibles associated with building system features
such as computer wiring…" (e.g., CMP cables [author’s
note]). Sprinklers are not required if cables are put in metal
conduit. Sprinklers are not required if exposed limited
combustible cables are installed outside of conduit. The
latter is by far the most cost effective, safe solution for
building owners.
It remains to be seen whether newer,
limited combustible cables, designed to meet the original
intent and requirements of both NFPA 90A and NFPA 13 will
eventually find their way into the NEC.
Figure
4. NEC definitions
Figure
5. NEC cable removal
Figure
6. NFPA Standards 90A, 75, and 76
The
Challenge for Electrical Inspectors
The scope of responsibility and breadth of code knowledge
needed by electrical inspectors are enormous and difficult
challenges. Hopefully, this article sheds some light on the
necessity to enforce the removal of abandoned communications
and other low-voltage cabling in buildings where mandated by Code.
As learned from many fires where low-voltage cables
contributed to the spread and intensity of the fire, cable
fuel load can be a major hidden hazard. Enforcement of code
requirements to remove abandoned cable is not just good
construction practice, but an important life safety issue.
When it comes to fire protection there is no room for error.
Frank Peri is president of
Communications Design Corporation, a leading network
infrastructure consulting firm. Mr. Peri is also an
active member of the NFPA and serves on several NFPA
Technical Committees. He can be reached at cdc@dmv.com.
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