Network Cabling Specification and Installation Practices Impact Building Safety

Advances in technology offer alternatives to traditional cable materials
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Generally speaking, the following codes govern communications cables:

NFPA 90A-Standard for Air Conditioning and Ventilation Equipment

NFPA 90A is responsible for plenum spaces in buildings. In the 2002 Edition, this standard sets requirements for flame, smoke and fuel load in the following section: 4.3.10.2.6-"All materials exposed to the airflow shall be non-combustible or limited combustible and have a maximum smoke developed index of 50..." (From the 2002 edition). This refers to NFPA's smoke index rating and a flame spread index rating.

Under this code, combustible cables are allowed as an exception.

When designing network infrastructure to a standard of protection as opposed to minimal code compliance, it is advisable to design to the NFPA 90A primary requirement that all materials installed and exposed to environmental airflow be noncombustible or limited combustible as opposed to compliance with wire and cable exception. LCC cabling meeting the requirements of NFPA 5000 model building code, and NFPA 13 model sprinkler code for limited combustible materials allows it to be installed in virtually any noncombustible building construction without the need for additional fire protection (sprinklers or noncombustible conduit).

The NFPA 70-National Electrical Code (NEC) is responsible for cable products and applications

This code recognizes need for higher fire safety performance for cables installed in plenums. NEC 2002 requires removal of abandoned cable from plenums. NEC 2005 acknowledges that plenum (CMP, CATVP, OFNP) cables are combustible with reference to NFPA 13 requirements for protection of concealed spaces

NPFA 13 sets the requirements for sprinklered buildings

Plenum-sprinklers are required in sprinklered buildings if there is a loading of unprotected ‘combustible' materials such as like traditional CMP, OFNP, CATVP, etc. plenum cables. In sprinklered buildings, use of combustible cables in concealed spaces, including plenums, requires installation of sprinklers in these spaces. However, use of limited combustible cable does not require sprinklers in these spaces. The options are clear: either install sprinklers in concealed spaces, or use the more cost-effective LCC cable.

NEC 2005 now refers users to NFPA 13 (2002) for guidance on fire protection needs for traditional ‘combustible' plenum cables.

Because existing fire codes were established as a result of the testing and analysis of many organizations and knowledgeable engineers, many consider that merely meeting existing fire codes is sufficient. However, many of the standards regarding the flammability of communications cables were developed over two decades ago, when building cabling referred to a few telephone service cables. With a phone on each office desk, and a centrally-located PBX-type switch, the amount of cabling was extremely limited by today's standards. Computer networks continue to increase, as does the amount of electronics and the size of buildings-all of which point to a much greater fire risk. With the spread of sensitive electronics comes greater dependence on these systems, so that fire and smoke damage will almost certainly exact a greater financial toll today, than when these standards were first developed in a markedly different business and technological environment. In fact, a case can be made that many of the existing safety standards were developed to correspond to circumstances that are non-existent today-and that have evolved over time to pose far more hazards with the potential to generate a host of negative consequences.

An Effective Program for the Future

With the enormous amount of cable present in commercial buildings required to service the ever-increasing demands of IT networks, fire safety is a growing concern. Many leading cable system suppliers offer LCC with advanced fire resistant capabilities that exceed code and contribute to sustainability. As pending codes are adopted, LCC may allow building owners to do without plenum sprinklers. In jurisdictions requiring that CMP cabling be installed inside metal conduit, LCC may replace both. In such cases, LCC may be more desirable than CMP-rated cable in terms of cost and convenience. A UL-listed LCC system combined with a program to remove abandoned cables represents a proven, effective way to reduce the risk of personal injury or death, property damage or business loss, addressing contemporary needs and contemporary circumstances.

 

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Originally published in Architectural Record.
Originally published in December 2006

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