In Tandem
NFPA 72, NFPA 101, and fire alarm system requirements
NFPA Journal®, November/December 2012
Provisions for installing a fire detection and alarm system are included in NFPA 72®, National Fire Alarm and Signaling Code, but the code does not state when a fire alarm system or detection is required—that’s the job of NFPA 101®, Life Safety Code®. The Life Safety Code specifies when a fire alarm system or fire detection is required in the .3.4 subsection, “Detection, Alarm, and Communications Systems,” of each occupancy chapter. However, it is important to understand that the Life Safety Code also includes criteria detailing the way the alarm system is to operate.
For example, paragraph 9.6.3.2.1 of the Life Safety Code states that smoke detectors used solely for elevator recall, and heat detectors used solely for elevator power shutdown, are not required to activate the building fire alarm system. Paragraph 9.6.3.2.2 states that smoke detectors used solely to close dampers or shut down the HVAC need not activate the building fire alarm system. And paragraph 9.6.3.2.3 states that smoke detectors used for automatic closing doors — doors that are held open with a magnetic hold-open device — are not required to activate the building fire alarm system. In all three cases, the detectors are required to transmit a supervisory signal to a constantly attended location.
Paragraphs 9.6.3.5.5/6 permit the deletion of visual alarms in exit stair enclosures and elevator cars, while paragraphs 9.6.3.6.4/5 permit the deletion of audible alarms in exit stair enclosures and elevator cars.
Audible and visual alarms in stairs present two problems. One is the excessive noise and visual distraction they produce while a building, especially a tall buildings, is being evacuated — imagine what it’s like to walk down 87 stories in a stairwell, surrounded by hard surfaces, with loud audible alarms blaring and bright flashing lights. The other problem is when the building has zoned evacuation, as in a high-rise building, where only the fire floor, the floor above, and the floor below are evacuated on the initial alarm, yet occupants located near the stairs throughout the building can hear the alarm in the stairwell. This can result in considerable confusion, questions from occupants about why the alarm hasn’t activated on their floor, or assumptions by occupants that the alarm system isn’t working correctly.
The Life Safety Code also permits the fire alarm system to not activate throughout the entire building under two conditions. The first is where total evacuation is impractical, such as in high-rise buildings or large shopping malls. In these cases, zoned evacuation is permitted.
The second condition is where the occupants are incapable of evacuating themselves, as they are in jails, prisons, or health care occupancies. In these occupancies, the Life Safety Code permits the use of the private operating mode as described in NFPA 72.
Consider a patient in a cardiac care unit recovering from a major heart attack when a 120-decibel horn on the wall beside him suddenly activates or a surgeon about to make an incision when the horn beside her activates. The private operating mode allows a coded announcement, such as “Dr. Red, Dr. Red report to room 234,” to alert staff. The staff knows that the code “Dr. Red” means a fire alarm.
These are just some of the reasons you must carefully review the specific occupancy chapter requirements of the code, as well as those general requirements in Chapter 9 for other fire alarm system operational requirements.
Chip Carson, P.E., is president of Carson Associates, Inc., a fire engineering and code consultancy.