NFPA Journal

As part of its efforts to make the survivability requirements in NFPA 72, National Fire Alarm and Signaling Code, easier to understand and apply, the Chapter 24 technical committee is proposing important changes to the 2022 edition of the code.

Many designers and contractors do not include survivable cable or fire-rated enclosures in their designs for in-building fire emergency voice/alarm communications systems (EVACS) wiring as required in the code—or at least not until the authority having jurisdiction enforces the requirement because a designer missed it the first time around. This may be due in part to some confusion over where survivability is required in the first place. Pathway survivability is not required for all EVACS; it is only required where occupants will remain in the building during an emergency (i.e., relocation or partial evacuation). The intent is to ensure that we can still get subsequent instructions to those occupants if the situation worsens. For those systems where pathway survivability is required, it does not necessarily need to be applied throughout the entire system; it must be applied only where the circuit runs through multiple notification zones, so that a fire in one notification zone doesn’t impair the ability to communicate with occupants in another. Additionally, the current edition of NFPA 72 permits the installer to use Level 1, Level 2, or Level 3, meaning that a sprinklered building (i.e., Level 1 pathway survivability) does not require the use of fire-resistant cabling or an enclosure. No wonder a contractor or installer might not include fire-resistive cable in an initial design.

The reason behind survivability requirements is to maintain the operational reliability of the EVACS during a fire. Pathway survivability for emergency communications systems (including EVACS) is covered in 24.3.14; Section 12.4.5 includes the definition of Level 4 pathway survivability.

The previous requirements for survivability said only that the cable had to be two-hour-rated or installed in a two-hour-rated enclosure. The technical committee changed the requirement so that it is now related to the fire resistance rating of the building construction. This relationship is important because the listing of two-hour fire-rated cable is required to be attached to a concrete wall or floor assembly, constructed with a minimum of two-hour rating or as otherwise identified by the UL FHIT systems assembly.

Additionally, as stated in the Annex A of the code, “installing a pathway survivability Level 2 or Level 3 in a building that is constructed with less than two-hour construction would not be installed within the listing of the product.”

For building construction with a fire-resistance rating of one hour, but less than two hours, the technical committee has proposed a new Level 4 pathway survivability.

With the more common use of timber construction for larger buildings, the expectation is these buildings would be classified as one-hour fire rated. Two-hour cable, as it is presently listed, would not be allowed when using the proposed Level 4 wiring or with wiring that meets the proposed separation requirements. That prohibition is due to the concern that a fire causing an open, ground-fault, or short-circuit fault on the communication and control circuits between rooms or enclosures could affect the operation of the in-building fire emergency voice/alarm control equipment within these rooms or enclosures.

It is well known that the insulation on fire alarm cabling can melt when exposed to heat and flames, causing the conductors to short circuit. When this condition occurs, it is possible for an entire signaling line circuit to fail, seriously impacting communication and control circuits. To help guard against these kinds of catastrophic failures, the proposed code would require the use of fault circuit isolators to ensure that the entire circuit is not disabled during a fire.

These proposed changes to the 2022 code would provide guidance in Annex A to assist designers, contractors, and AHJs in the proper separation of circuits as well as the location of fault circuit isolators to ensure both compliance with the code and a high degree of operational reliability. It is important to remember that for fire alarm systems designed for relocation and partial evacuation, communication must remain operational on all floors other than the fire floor during a fire. The primary fire protection goal is reliable communication during the fire. 

Wayne D. Moore is vice president at Jensen Hughes. NFPA members and AHJs can use the Technical Questions tab to post queries on NFPA 72 at nfpa.org/72.