NTC Blog

Operating Mode

Thu, Sep 10 2020 at 11:00 AM

Notification appliances provide notification to individuals in a protected building by providing audible or visible notification. The specific individuals intended to be notified by the notification appliances determines the operating mode of the appliance.

 

Public mode notification is the most common notification for fire alarm systems. Audible levels are required to be 15 dB above average ambient, or 5 dB above the maximum sound level with a duration of at least 60 seconds measured 5 feet above the floor using the A-weighted (dBA) scale. Visible notification requirements are based on room size and location of strobe(s) per Tables 18.5.5.1(a) (wall mount) or (b) (ceiling mount).

 

Private operating mode provides notification only to those individuals directly concerned with implementing or directing the emergency action plan. Private mode is the less common operating mode because it is intended to notify only those key responsible individuals.

 

Unlike public mode audibles, private mode audibles are only required to be 10 dB above average ambient sound level. Private mode visible notification appliances are not required to comply with the visible notification spacing requirements in NFPA 72 18.5.5.1(a) or (b). Private mode visible notification appliances are required to be of sufficient quantity, intensity, and location to meet the intent of the user and the AHJ.

 

A common application of private mode notification is in a hospital patient care area. Since the patients are not capable of self-preservation, having audible and visible notification throughout the area could be problematic. Rather, an audible and visible notification appliance would be located in a constantly attended location such as a nurse’s station.

 

NFPA 72 also permits private mode notification in elevator cars and restrooms with AHJ approval.


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