Code Question — My AHJ wants me to put a strobe in an office area with two desks. Is this a requirement of the IBC or NFPA 72?
The IBC (International Building Code), determines the fire alarm requirements for a building. Based on the building classification (Use Group), Section 907 tells us what type of fire alarm is required (manual fire alarm (pull stations) or automatic fire alarm (smoke detectors). The specific fire alarm requirements for a building are located in Section 907.2, organized by Use Group.
In addition to determining the type of system required, the IBC also determines fire safety functions (907.3), initiating (907.4), notification (907.5), and installation and monitoring (907.6) requirements. The IBC determines building requirements for these aspects of the fire alarm system, and then refers to NFPA 72 for specifics of location and spacing.
Section 907.5 requires that a fire alarm system activate occupant notification when the fire alarm system is activated by automatic detection, manual fire alarm boxes, sprinkler system waterflow, or automatic fire extinguishing system.
Notification is by audible and visible notification appliances per the requirements of 907.5. 907.5 may require standard audible notification (horns) or voice notification (speakers), depending on the building classification and occupant load. The IBC also states exceptions to audible and visible notification requirements that may apply under specific applications or instances.
907.5.2.1 cover audible notification requirements and requires audible notification in every occupiable space of the building be provided at least 15dB above average ambient sound level. 907.5 also sets a maximum sound level for notification appliances of 110dB at minimum hearing distance, so it permits visible notification only in areas with an ambient sound level greater than 95dB.
907.5.2.3 covers visible notification requirements and requires visible notification in public use areas and common use areas. The terms “public use area” and “common use area” are defined in Chapter 2 (Definitions) of the IBC. If you are reading in the IBC, you may notice that these terms are italicized. Italicized terms in the IBC indicate they are defined in Chapter 2.
Chapter 2 defines a public use area as room or space available to the general public. Chapter 2 defines a common use area as a path, room, or space not for public use that are available for shared use by two or more people. The office area with two desks in question would fall under the common use area definition, so it would require visible notification per IBC.
The actual strobe requirements would then come from NFPA 72, Chapter 18 (Notification Appliances). The strobe intensity requirements will depend on whether a wall mount or ceiling mount strobe is used, and then refer to the tables in Chapter 18 for specific requirements. For wall mount, room dimensions and whether you are using one or four strobes determine the requirement. For ceiling mount, room dimensions and ceiling height determine the requirement.