The last few code cycles have introduced an increasing number of performance-based allowances into NFPA 72, the National Fire Alarm and Signaling Code. Performance-based design of detection systems, visible notification appliances, emergency communications systems and performance-based testing are now permitted. As we know, all buildings are not created equal, and trying to meet NFPA 72’s minimum prescriptive-based requirements sometimes can be a challenge. Performance-based design increases the need to have a much more qualified designer and a qualified authority having jurisdiction (AHJ). The AHJ must be knowledgeable enough to determine if the performance-based design meets the code’s intent and provides equivalent protection of the prescriptive-based requirements.
Chapter 17 of the 2013 NFPA 72, states, “Performance-based designs submitted to the authority having jurisdiction for review and approval shall include documentation, in an approved format, of each performance objective and applicable scenario, together with any calculations, modeling, or other technical substantiation used in establishing the proposed design’s fire and life safety performance.” It continues in 17.3.2 and 17.3.3 with, “The authority having jurisdiction shall determine whether such identified performance objectives are appropriate and have been met,” and, “The authority having jurisdiction shall approve modifications to or variations from the approved design or design basis in advance.” Annex B, Engineering Guide for Automatic Detector Spacing, provides the basis for implementation of performance-based design of fire alarm detection systems.
Chapter 18 allows a performance-based alternative for strobe design. It states, “Any design that provides a minimum of 0.0375 lumens/ft2 (0.4036 lumens/m2) of illumination at any point within the covered area at all angles specified by the polar dispersion planes for wall- or ceiling-mounted visual appliances in ANSI/UL 1971, Standard for Signaling Devices for the Hearing Impaired, or equivalent, as calculated for the maximum distance from the nearest visual notification appliance, shall be permitted in lieu of the requirements of 18.5.5, excluding 18.104.22.168.” Many facilities present challenges to mounting strobes at the required heights of 80 to 96 inches. This alternative approach must still meet the intent of the code and the Americans with Disabilities Act by proving an acceptable level of illumination.
Annex A.22.214.171.124 states, “A design that delivers a minimum illumination of 0.0375 lumens/ft2 (footcandles) [0.4037 lumens/m2 (lux)] to all occupiable spaces where visible notification is required is considered to meet the minimum light intensity requirements of 126.96.36.199.2(1). This level of illumination has been shown to alert people by indirect viewing (reflected light) in a large variety of rooms with a wide range of ambient lighting conditions.
“The illumination from a visible notification appliance at a particular distance is equal to the effective intensity of the appliance divided by the distance squared (the inverse square law).”
Annex A provides enough insight to perform the necessary calculations to determine the illumination that will meet the code’s intent.
Emergency Communications Systems, a new chapter in the 2010 edition, allows a performance-based design of mass notification systems in 24.7 and provides the goals and objectives to be met:
1. “The risk analysis, design criteria, design brief, system performance, and testing criteria are developed in accordance with this section.
2. “The system disseminates information to the target audience in an accurate and timely manner.
3. “The design and performance criteria are specific to the nature and anticipated risks of each location.
4. “The system is capable of withstanding various scenarios and survives even if some damage has already occurred.
5. “Message initiation can be effected by all responding entities responsible for the safety and security of occupants.”
NFPA 72 also allows a performance-based approach for testing of fire alarm systems. The NFPA Fire Protection Research Foundation is conducting a study to provide better information regarding the testing frequencies that are in the code. Section 14.2.9, Performance-Based Inspection and Testing, states, “As an alternate means of compliance, subject to the authority having jurisdiction, components and systems shall be permitted to be inspected and tested under a performance-based program.”
A.14.2.9 states,“The prescriptive test and requirements contained in this Code are essentially qualitative. Equivalent or superior levels of performance can be demonstrated through quantitative performance-based analyses. This section provides a basis for implementing and monitoring a performance-based program acceptable under this option (provided that approval is obtained by the authority having jurisdiction).”
The goal is to balance inspection and testing frequency with proven reliability of the system or component and to adjust inspection and testing frequencies based on historical documented equipment performance and desired reliability.
Performance-based design and testing can provide more flexibility for a given facility, but this process requires a much higher level of knowledge and understanding than a typical prescriptive design or test. Make sure you’re in the know.