Sense and ‘Survivability;

Survivability, as defined by NFPA 72, has long been a confusing issue for engineers, installers and AHJs (authorities having jurisdiction) alike. Code requirements, which have been revised through the years, have meant to safeguard voice evacuation systems in the event of fire. In the past, however, the code requirements did not address issues such as design quality and installation, especially for complex fire alarm systems installed in high rises and most hospitals. 

Uncertainty has continued to arise when asking just what exactly is survivability and why is it required? What greater good does it ensure for a building and the occupants? Beyond the questions surrounding the implementation of survivability, even more perplexing is how to design for it and its installation requirements. 

To bring clarity to this topic, the best place to start is to define what survivability is, and then allow the rest of the puzzle pieces to fall into place. Also in this story, a wiring schematic of a typical voice evacuation system is detailed with a straightforward explanation. 

Survivability Code Requirements Began With 3 Options
Simply, survivability addresses the requirements for a voice evacuation system to remain viable for at least two hours in areas not associated with a fire incident, thereby allowing occupants to be notified of an evacuation or provided other emergency communications. This system also includes the visual notification circuits for the facility. 

The survivability section in the 1999 edition of NFPA 72 was provided in Under this section, the allowable ways to achieve survivability were to install the circuits in one of three options: 1) a two-hour rated assembly; 2) a two-hour rated shaft or enclosure; 3) a two-hour rated, fully sprinklered stairway. However, these definitions offered no engineering guidance in the code or appendix instructing how or when to install these requirements for partial evacuation systems.

When talking about option 1, architects usually had issues in providing more structural components to achieve the two-hour rating, and this often interfered with desired aesthetics. Hence, option 1 needed the architect’s cooperation early in the project. 

Option 2 proved easier to achieve if the electrical rooms were two-hour rated and were stacked directly above each other. Unfortunately, this often wasn’t the case. Again, this required the cooperation of the architect early in the project’s design, and not at the shop drawing level.

The third option was the least viable. The International Building Codes do not allow fire alarm risers in exit stairways without the building code officials willing to authorize an administrative modification to the building code in order to put the riser in any staircase. 

Subsequent Code Revisions Did Not Entirely Alleviate Confusion
In the 2002 edition of NFPA 72, the confusion continued with the survivability section, renumbered as, and the appendix of this section providing the possibility that a fully sprinklered building would help satisfy the requirements of this section under (3). Again this left the fire alarm community confused on the application of this section. Here, under, three options are allowed, although slightly different: 1) a two-hour rated cable or cable system; 2) a two-hour rated enclosure; 3) performance alternatives approved by the AHJ. 

Confusion remains on how to apply this section. Option 1 became available with the invention of the circuit integrity (-CI) cable with its approved installation assembly. The second option is still at the feet of the architect to issue a change order for the enclosure. Finally, few, if any, AHJs are allowing anything under the third item. While option 3 is not impossible, it does require the fire alarm system installer to convince the AHJ that the option is viable: this most often requires employing a licensed fire protection engineer who is usually not on the payroll of the fire alarm installer. 

Voice Evacuation Plans Need to Be Addressed During Building Design
It is great to have something in writing for the definition of survivability; however, there were no guidelines on how to apply this information or what the intent is on the installation. Recently, several respected engineers, code officials and NFPA staff have been interviewed on how to apply survivability to real-world problems and engineer a successful system that complies with NFPA 72 without a lot of excess cost to the facility owner. 

It is apparent that a fire alarm solution with partial voice evacuation needs to be crafted at the early stages of a building design. The survivability options should be presented to the architect, electrical engineer and the mechanical engineer before construction of the building commences. 

It has been clarified by the interviewed engineers, code officials and NFPA staff that anytime a voice evacuation system is installed, and partial evacuation is in the sequence of operation, the survivability requirements of section 6.9.4 are required. With this requirement confirmed, it is clear that a facility that has full voice evacuation is not included and, therefore, does not fall under this section requiring the survivability of the circuits. 

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