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Building Operating Management

Cabling



Reducing Fire Risks Target of New Code


By Mike Lobash   Power & Communication

Cabling

Following years of acquiring the infrastructure necessary to satisfy and attract building occupants with high-speed facility voice and data capabilities, building owners are now charged with improving the safety of the information highway.

Communications cabling systems — the conduit that makes the virtual world leap to life — are subject to new rules aimed at reducing fire risks associated with the low-voltage cables.

Under the current version of the National Electrical Code, unused cables not marked for future use are no longer allowed in ceiling and floor plenum spaces. Building owners — or tenants, depending upon how a lease is structured — are required to remove the cables.

The change comes after years of testing and research indicating that combustible cables burn in fires and emit smoke that impedes building evacuation, contains a lethal amount of toxin, and damages sensitive computer and electronic equipment.

Matters of Local Concern

Exactly which buildings will be subject to the new regulations is still being determined. Although the National Fire Protection Association develops and promulgates the National Electric Code, it is up to individual states, counties and municipalities to adopt the code. A handful of states, including Massachusetts, Minnesota, North Carolina and New Hampshire, have already adopted the new requirements. Others are still reviewing its ramifications.

Most noteworthy in the new code is the requirement that accessible portions of abandoned cables be removed from air plenum spaces. There is an exception — some call it a loophole — that allows cables with connectors on both ends or cables tagged for future use to remain in the plenum.

Inaccessible cables, such as those embedded in concrete floors — also known as cellular floors — or permanently built into structural members, don’t fall under the new requirement.

Because facility executives have never been required to remove abandoned cable, it’s very likely that cable trays in most buildings are chock full. And the older the building, the more likely the chances that it contains a mess of cables. It’s possible that new cables were put in place each time building occupants changed or every time a networked technology was installed. That complicates the task of removing old cables. Unless cables are properly tagged — an often-ignored practice — there’s a chance of removing a cable that is in use.

“Most people just don’t take the time to develop the documentation,” says Frank Peri, president of Communications Design Corp., a Maryland-based consulting firm that specializes in structured cabling systems. “The biggest risk in removing them is making sure you don’t cut the wrong cable.”

Without documentation indicating that a cable is active, removing them is an arduous task. Following each cable to its termination point to see if it is connected to equipment can be time consuming and expensive. Labor expenses can add up rapidly because most of the work of tracking and removing cables would be done after business hours when labor rates escalate, Peri says. It’s impractical to remove cable from an existing building during work hours because the access workers need to plenum spaces would interfere with occupants.

As a result, Peri says he expects most cables will be removed when facilities are undergoing substantial retrofits.

The new provision to require the removal of abandoned cable is the first change to cabling requirements in the National Electrical Code in more than 20 years. In 1975, NFPA made an exception to NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems, which requires any materials installed in a plenum space to be either “noncombustible” or “limited combustible.” The exception was made because when the codes were drafted more than 25 years ago, neither limited combustible nor noncombustible cables had been developed. Those cables have only been available for the past two years or so.

Ensuing Issues

So while that exception is still made today, allowing tagged cables or those with connectors to remain in plenum spaces, there is ongoing debate over whether that exception should remain in the National Electric Code. NFPA 90A does not permit anything but active cables to remain in plenum spaces, requiring removal of even tagged cables and those with connectors. Reconciling what types of materials are required to be used under the conditions of NFPA 90A and what materials are allowed under the National Electric Code is likely to be a focal point in formulating the next edition of the electrical code.

Regardless of how that matter sorts itself out, the change in the 2002 National Electrical Code requiring the removal of abandoned cable is a recognition of the amount of fuel load contained in plenum spaces as a result of cable installations, Peri says.

In 1991, it was estimated there were approximately 5 billion feet of plenum cable in place in the United States. That estimate grew to 30 billion feet in 1997 and 45 billion feet in 2000. Statistics indicate that buildings are recabled every three years with the existing cable being left in place.

If the cable were to catch fire in a building, it raises a number of concerns, says John Michlovic, manager of marketing and technical services for Centria H.H. Robertson Floor Systems, maker of a cellular floor system that houses any type of communication cable.

First, Michlovic says, the combustible plastic insulation in a heavily cabled plenum can burn with a btu content similar to gasoline. Secondly, even though cables commonly found in plenums today contain flame-retardant jackets, older cables with split or deteriorated jackets in which the cable insulation is exposed spread flames more rapidly than allowed by NFPA Standard 262, which limits flame spread to 5 feet in 20 minutes.

Lastly, Michlovic says, burning plastic of any kind releases toxic gases. In access floor plenum spaces, the toxic gases released in a fire can be concentrated at floor level where people attempt to crawl out of a fire.

Fire safety isn’t the only issue raised by abandoned plenum cabling. Most of the cable in buildings today, known as communications multipurpose plenum (CMP), is jacketed with fire-resistant polyvinyl chloride. Two components used in making the polyvinyl chloride are lead stabilizers and plasticizers, which allow the material to remain flexible.

In recent years, tests have indicated that the lead content in the cable jacket could be anywhere from 2 to 8 percent by weight, says Frank Bisbee of Communications Planning Corp. in Jacksonville, Fla. That equates to about 1 1/2 pounds per every 1,000 feet of cable, meaning the concentration is about 30,000 to 40,000 parts per million.

The Environmental Protection Agency limits lead exposure to 220 parts per million. The biggest risk to exposure is when the cable is being installed, Bisbee says. Chaffing the cable jacket against hands, cable trays or other structural elements could cause lead to be released.

The makeup of the cable jacket also complicates its disposal. Bisbee says the EPA is very close to classifying the material as a hazardous substance, meaning it could not simply be thrown away or recycled. Its disposal would require handling by special waste haulers, further increasing the time and expense necessary to remove abandoned cable.

Bisbee says he suspects it’s simply a matter of time before the scientific research indicating the dangers of the cable material results in rules and regulations governing the material’s use and handling. Such a move could open building owners to lawsuits claiming that occupants have suffered health problems as a result of lead exposure.

“We thought we had Satan’s block when we uncovered asbestos,” he says. “This stuff is in every building in the United States.”

One way building owners could limit liability, Bisbee says, is to begin specifying the type of material that occupants are allowed to put in buildings. There are alternative ways to wire buildings without using plenum-rated cable.

One is to use limited-combustible cable, which doesn’t contain the same level of toxins and lead as plenum-rated cable. Available for the past few years, limited-combustible cable is beginning to be used in new construction and renovation projects. In addition to having fire-resistance characteristics similar to concrete, limited-combustible cable is recyclable once removed.

Cy Genna, datacom program manager for DuPont, which manufactures insulation and jacket materials used in limited-combustible cable, says he expects the technology to replace CMP cable over time. As abandoned CMP cable is removed, it will be replaced with limited-combustible materials.

Business Benefits

One of the first building types to use limited-combustible cable is data centers. It’s installed in those facilities not necessarily to improve life safety but to ensure building continuity.

Genna says facility executives at data centers use the cable because it emits far less smoke than traditional plenum cable. In the event of a fire, the smoke damage to computer equipment in a building fitted with limited-combustible cable is far less than that occurring at buildings with plenum-rated cable.

Another alternative to plenum-rated cable is to abandon the use of plenum space for cabling. There are cellular floor systems available that allow cables to be installed within steel cells after the concrete is poured to create floor slabs. The cable can then be accessed through floors and networked to equipment.

Michlovic of Centria says that cellular systems offer greater protection to facilities and occupants from fire and smoke than the use of plenum-rated cable.




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  posted on 1/1/2003   Article Use Policy

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