NFPA Journal

The proposals have been submitted for the 2022 edition of NFPA 72®, National Fire Alarm and Signaling Code®, and pathway survivability appears to be an area of the code that a lot of people have an interest in changing.

Pathway survivability is defined in NFPA 72 as “the ability of any conductor, optic fiber, radio carrier, or other means for transmitting system information to remain operational during fire conditions.” The performance requirements for survivability have been included in the code since its first edition in 1993. The 1999 edition was the first to allow three different specific methods to achieve survivability, while the 2019 edition includes the following: “Fire alarm systems used for partial evacuation and relocation shall be designed and installed such that attack by fire within a signaling zone does not impair control and operation of the notification appliances outside the signaling zone.”

The requirement also applies to circuits and equipment that are common to more than one signaling zone. For example, when a signaling line circuit is used to control notification appliances in multiple notification zones, it should be properly designed and installed so that one fire would not impair more than one notification zone. Chapter 12 does not require any specific pathway survivability method as defined in that chapter. Submitted changes to this performance-based approach for the 2022 edition were rejected by the technical committee.

None of the Chapter 12 pathway survivability requirements apply until another section of NFPA 72 or another code requires survivability. In the case of NFPA 72, Chapter 24 requires specific levels of survivability for all in-building fire emergency voice/alarm communications systems (EVACS) where partial evacuation or relocation takes place.

During code cycles for the 2016 and 2019 editions of NFPA 72, the requirements were changed to permit Level 1, 2, or 3 survivability in buildings constructed with less than two-hour construction. During that same cycles, the concept of Class N and X circuits that were separated by one-third of the diagonal of the notification zone was introduced again, allowing the installation to permit Level 1, 2, or 3 survivability in buildings constructed with less than two-hour construction.

However, it has since been determined that the listing of either two-hour fire-rated (circuit integrity) cable or a two-hour electrical circuit protective system 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 fire-resistive cable systems assembly. Installing a pathway survivability Level 2 or Level 3 in a building that is constructed with less than two-hour construction would not be installing the two-hour fire-rated cable or a two-hour electrical circuit protective system within the listing of the product. In a fire event, the wall or floor assembly could fail, in turn causing the pathway to fail. Both NFPA 72 and the UL listing require all fire-rated cables and systems to be supported per the manufacturer’s installation instructions.

The 2022 edition of the code now has proposals to correct this and to develop a new level for survivability. The proposed code language develops the concept of a new “Level 4” survivability to accommodate buildings constructed with a fire resistance rating of at least one-hour and less than two-hour. The Annex A to the new Level 4 states that “the listing of one-hour fire-rated cable system [electrical circuit protective system(s)] would likely be required to be attached to a wall or floor assembly that is constructed with a minimum of one-hour rating.”

The concept of the one-hour fire-rated circuit integrity or fire-resistive cable system would mean that it would not need to be attached to a concrete wall or floor, but simply be supported in accordance with the manufacturer’s installation instructions. It should be noted, however, that the UL testing requirements will need to be modified for one-hour cable listings.

Although the proposed re-write of the survivability section of the code has some merit, it should be noted that at the present time, listed one-hour fire-rated circuit integrity or fire-resistive cable system does not exist in the United States. The technical committee feels that cable manufacturers will address this issue once the code has been approved at the next NFPA annual meeting. 

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.