Since the 1980s, the National Fire Protection Association’s fire alarm standards have required the notification appliance (speaker) circuits used in high-rise building Emergency Voice/Alarm Communications systems to “survive” during a fire. While the standards did not explicitly define the term “survivability,” methods to meet performance requirements for survivability first appeared in NFPA 72F-1985, Standard for the Installation, Maintenance, and Use of Emergency Voice/Alarm Communications.
The performance requirements for survivability have not changed since the 1985 edition of the standard. The 1993, 1996 and 1999 editions of the National Fire Alarm Code have had similar performance requirements.
The requirements for fire alarm circuit survivability apply only to a small percentage of systems where the evacuation plan for the building calls for partially evacuating building occupants or relocating them in the event of a fire. Those who developed the concept of survivability intended it to minimize the possibility of attack by fire interrupting communication to areas outside the fire area. For example, circuits that serve various floors in a multi-floor building may pass through areas where a fire might threaten them before they reach the floor(s) they serve. Providing fire-rated construction, a fire-rated cable, or a fire-rated cable assembly minimizes the possibility of impairment of service to areas outside the fire area.
For years, to meet survivability requirements, installers would follow a standard procedure and install standard cables in raceway in a two-hour rated shaft. More recently, manufacturers have developed two-hour fire-rated circuit integrity (CI) cables. Underwriters Laboratories Inc. (UL) tested these cables under the robust test parameters of UL 2196. Unlike its European counterpart testing laboratories, UL attaches the electrically energized cable on a firewall, and subjects the cable to the standard time/temperature curve growing to 1,800 degrees Fahrenheit for two hours. The test technicians then remove the cable from the fire, shut off the power and spray the cable with water, using a standard fog nozzle. The test technician then reapplies power and all devices connected must still operate. If the cable per-forms as required, it receives a “CI” designation. This cable does not require raceway unless installation circumstances require mechanical protection.
The manufacturers introduced these cables as an economical alternative to more expensive cables that installers also find more difficult to work with. The new cables further provide an alternative to enclosing nonrated cables in a two-hour rated shaft or two-hour rated enclosure.
Some critics of CI cable claim that a “new” code requirement has forced designers and installers to use this new product. In reality, the code does not require anyone to use the two-hour rated cables. But, building a shaft in a high-rise building in some cases only to protect the fire alarm circuit risers does frequently cost more money and decreases the amount of leaseable space in a building.
Since the introduction of CI cable, some progressive designers have decided to use this cable everywhere they have circuits controlling critical life safety equipment. They believe that using CI cable will increase the chance that these circuits will endure the exposure to a fire long enough for the critical equipment—such as smoke control or elevator recall—to operate safely. Other designers require the use of CI cable when a signaling line circuit (SLC) may serve a large number of devices. This use attempts to address the “eggs in a basket” issue.
One might expect that practitioners would welcome a new technology that allows for easier and less costly compliance with a Code requirement with open arms. But, as with many new developments or products, some people will always resist change.
A few individuals question the need for survivability. Many of them simply do not understand the reasoning behind the requirements. They have the false impression that the survivability requirements intend to ensure the complete operability of the fire alarm system under all possible fire conditions. The survivability requirements have never intended such an all encompassing outcome.
The National Fire Alarm Code Technical Committee on Protected Premises Fire Alarm Systems recognizes, and the Code reflects the fact, that direct fire attack of fire alarm system components can compromise the operation of the circuits, devices and appliances serving the immediate fire area. In fact, the language of the Code requirements clearly recognizes that direct exposure to a fire may compromise specific fire alarm devices and components. Current code language recognizes that fire attack will impair circuits in the immediate fire area while the requirements intend to minimize the impairment of circuits that serve areas outside the immediate fire area.
Others resist accepting the new technology because they do not fully understand the requirements of the UL 2196 test. As previously stated, these rigorous tests go far beyond briefly subjecting a simple coil of cable to the heat from a hot plate or to the flame from a Bunsen burner.
In addition to these newly developed “CI” cables, some manufacturers make two-hour rated “cable assemblies.” One of these cable assemblies, known as a metal-clad (MC) cable, also has the “CI” designation. Installers primarily use the MC-type cables to meet the requirements of NEC Article 695-6 (b) Circuit Conductors. This wiring supplies power to a fire pump controller. In some configurations, these power supply conductors must have protection against fire to preserve the operational capability of the fire pump. UL-listed cable assemblies include specific installation requirements as part of the listing.
Of course, in addition to those who generally resist change, others may try to provide misleading information about the new CI technology. Whether motivated by competitive concerns or other issues, one must carefully consider any claims of “dangerous” features of the new products. For example, one of the “issues” presented by such people claims that the new cable, especially in the MC-type construction, emits flammable smoke when exposed to higher temperatures during a fire.
All wiring, except for Type MI cable, smokes when exposed to fire. Unlike typical building wire, such as Type THHN, where relatively low (minus 250 degrees Fahrenheit) temperatures generates smoke, the MC-CI cable doesn’t even start to emit smoke until temperatures exceed 800 degrees Fahrenheit. At such temperatures, the cable generates a small amount of smoke for approximately five to 10 minutes. This smoke occurs as a by-product of the ceramification process associated with the silicone construction that occurs only in the areas of fire exposure. Although the smoke contains flammable gases that may support combustion, to ignite the gases must exist in heavy concentrations, have a renewal oxygen supply and exist in the presence of a high-energy ignition source. Dissipation and condensation of gasses in the sealed M-C enclosure limits the ability of concentrated gases to find their way to an ignition source, such as an electrical panel.
Of course, if this issue offered a serious problem, UL would have included tests to determine the cable performance and acceptability under these conditions.
One has to remember that no ordinary occupants could survive in an 800 degrees Fahrenheit environment, so the issue of smoke production at these temperatures does not offer a real threat. And, even the firefighters who might come in contact with such smoke have the protection offered by their self-contained breathing apparatus.
I encourage the detractors of CI cable to see the merits of this new technology. CI cable offers an easier way to meet a long-standing requirement in the Code. The goal of those requirements remains the same: to improve the reliability and operation of critical notification, power and control circuits during the early stages of a fire.
Designers may indeed use this new technology to improve the fire performance of other products used in our fire alarm systems.
I encourage designers, code officials and installers to embrace this change in technology. Especially when that change offers the benefits of improved performance of building fire alarm systems. EC
MOORE, a registered professional fire protection engineer with a master’s degree in that area, has more than 30 years of experience in the fire detection systems field. He has contributed as both author and editor on many articles and book projects, including NFPA Fire Protection Handbook, Fire Alarm Signaling Systems Handbook, and two versions of the National Fire Alarm Code Handbook. Moore, who is an instructor and recognized expert, serves as ELECTRICAL CONTRACTOR’S contributing editor for fire/life safety.