Aug 24 2017

Silencing Audible Fire Alarm Signals

Category: Fire Alarm,Questions and AnswersBKeyes @ 12:00 am

Q: Recently we had an actual fire that set off our fire alarm. Our operators did not silence the audible horns, which are very loud, before announcing the code and location, thus the location was not known to most of the hospital staff. At our recent Safety Committee meeting this was discussed and it seems that some people believe that the audible should either not be silenced or delayed until after the code is announced overhead, then be activated. I have always instructed the operators to let the audible signals go for about 30 seconds then silence the audibles, and announce the location of the fire. The strobes do remain on until the alarm is cleared, and then only the safety officer or designee can reset the panel. If the panel is reset then the all clear is announced. So the question is, can the audible signals be silenced during an activation?

A: I’m concerned by your comment that the audible notification devices are ‘very loud’. I think you need to first address this issue to make sure you’re compliant with the intent of the National Fire Alarm Code (NFPA 72-2010). Section 18.4.4 of the 2010 edition of NFPA 72 discusses the requirement for Private Mode audible requirements. Most hospitals are designed to meet the requirements of ‘Private Mode’ rather than ‘Public Mode’ when it comes to fire alarm occupant notification. There are significant differences not only in the location of audible devices, but in the decibel requirements as well. Section (for Private Mode) of NFPA 72-2010 says the audible signals must have a sound level of 10dB above the average ambient sound level, or 5 dB above the maximum sound level, measured 5 feet off the floor. This signal is required to annunciate for at least 60 seconds, so cutting off the audible alarm signal before 60 seconds would not be permitted. However, section of NFPA 72-2010 does say with the permission of the authority having jurisdiction (AHJ), you can reduce these requirements. But be careful with the AHJ issue, as the typical hospital has 5 or 6 different AHJs who evaluate for compliance with NFPA codes and standards:

  • CMS
  • Accreditation organization
  • State health department
  • State agency with authority over hospital design and construction
  • State fire marshal
  • Local fire inspector
  • Liability insurance company

Typically, the accreditation organizations do not approve design issues in hospitals, but the state and local authorities do. If you want to reduce the duration of the fire alarm audible signal, you would need to receive the approval of all the AHJs… not just one or two. That is not likely to happen. I could see more than one of your AHJs not wanting to put in writing that you can reduce a minimum level of life safety for your hospital. So, my advice is to do the following:

  • Take a look at the dB ratings and see if they exceed the required levels for Private Mode notification as described in; adjust them as needed to meet the dB rating listed.
  • Program your fire alarm panel to pause after 60 seconds of audible signal, to allow the operators to announce the location of the alarm.
  • Develop a coded notification system using chimes to provide a general location or area of the alarm. Most modern fire alarm control panels are capable of this style of notification, rather than a general alarm style. This way your staff can begin to respond to the general area of the alarm and within 60 seconds they will hear the overhead page where the alarm is precisely located.