A smoky issue

I am often asked, "Can I use nonplenum-rated cable inside a plenum- rated innerduct?" My stock answer has always been, "Do not put anything into a plenum space that is not plenum-rated per the National Electrical Code (NEC)." This includes the contents of a plenum-rated optical-fiber raceway....And while we were all out cabling the world, the National Fire Protection Association (NFPA--Quincy, MA) was busy changing the rules--or at least trying to.

I am often asked, "Can I use nonplenum-rated cable inside a plenum- rated innerduct?" My stock answer has always been, "Do not put anything into a plenum space that is not plenum-rated per the National Electrical Code (NEC)." This includes the contents of a plenum-rated optical-fiber raceway....And while we were all out cabling the world, the National Fire Protection Association (NFPA--Quincy, MA) was busy changing the rules--or at least trying to.

In January 1998, the NFPA Technical Committee on Air Conditioning accepted its own proposal (Log #CP14) 90A-28 for revision of the Standard for the Installation of Air Conditioning and Ventilating Systems, currently published as NFPA 90A-1996.

This proposal was to delete 2-3.10.1 (a) Exception No. 1 (a), which addresses electrical wires, and cables that meet NFPA 262, Standard Method of Test for Fire and Smoke Characteristics of Wires and Cables. Because of this deletion, we are now allowed to install plenum-rated cables in plenum spaces.

According to the committee`s substantiation of the proposal, the rationale for originally including the exception about 10 years ago was that telecommunications cable used in plenums would be present only in small amounts, in comparison to materials that comprise the plenum`s interior surface. They contend that such an assumption is no longer valid and that combustible materials are accumulating in plenums in ever-increasing amounts. This situation arises because telecommunications cables installed in the plenum are usually abandoned rather than removed when no longer in use.

The NFPA`s action started a panic, which resulted in a plethora of comments from the telecommunications cabling manufacturers and their material suppliers. While most demanded no change, others saw an opportunity to sell more material.

In the ROC (review of comments), which closed in October 1998, the Technical Committee on Air Conditioning agreed to return to the original language of 2-3.10.1 in the 1996 edition of NFPA 90A, with the following modification:

"Add a new subpart (g) to 2-3.10.1: Electrical wire and cable removed from service that is not listed as noncombustible or limited-combustible and does not have a maximum smoke-developed index of 50 shall be removed."

In the event of fire, the expected amount of smoke produced in the plenum is directly proportional to the fire load in the plenum. The intent is to control the fire load by the removal of retired cable, or, if it is left in place, to require that it meet the requirements of 2-3.10.1(a) or 2-3.10.5(a), not the exceptions.

The committee also stated that the revised comment clarifies the original intent of the committee without imposing a retroactive requirement and that the committee believes it should be up to the authority having jurisdiction to determine what comprises "termination of cable service."

So does this mean that if some communications plenum cable installed in a plenum space is not active, it must be removed?

Yes. Literally thousands of NFPA 262 cables that qualify under the exception but do not meet the requirements of 2-3.10.5(a) are acceptable if they are in use. But if one NFPA 262 cable that qualifies under the exception but does not meet the requirements of 2-3.10.5(a) is abandoned, then it must be removed "when the service requirement is terminated and new wire or cable is added."

While it is logical that requiring the removal of abandoned cable would enhance safety, we must ask, when and at what cost and inconvenience to the building occupants? Should it be done as soon as the patch cords are pulled or when installing the next generation of cabling? Does this mean that we would have to remove Category 3 cabling when it still supports the same services that it did the day it was installed and is part of a structured-cabling system? How can the various generations of cabling be identified?

For more information on how we can participate in the NFPA process, see www.nfpa.org.

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