Tuesday, March 17, 2015

Are Low Frequency Sounders Required by Your AHJ

520Hz Low Frequency Sounders 

"Effective January 1st 2014, audible appliances provided for the sleeping areas to awaken occupants shall provide a low frequency alarm signal that complies with the following:  (1) The alarm signal shall be square wave or provide equivalent awakening ability.  (2) The wave shall have a fundamental frequency of 520 Hz +/- 10 percent."

We got a glimpse of the future requirement in the 2010 Version of NFPA 72 section 18.4.5.3 page 102.  Here we could see that come January 1st 2014, there would be a requirement for fire alarm designers to use a 520Hz square wave low frequency sounder within all sleeping areas.  There have been multiple studies performed that validate the belief that a 520 Hz low frequency audible tone will have a greater chance at awakening a sleeping occupant.  The lower frequency also has greater chances of awakening people whom are intoxicated or hard of hearing.

Lets fast forward to the year 2013.  NFPA 72 version 2013 notes the same requirement in section 18.5.4.3 page 108.

Click to listen to a 520Hz Low Frequency sound file.  Or a 3KHz tone typically used prior to 520Hz requirements.

Now, here we are in the year 2016 and yet not everyone is following this standard.  You may ask yourselves why is our AHJ or authority having jurisdiction not requiring our fire alarm installation company to install the new 520Hz low frequency sounders for sleeping areas.  Keep in mind that the particular state you install fire alarms in may have an older code adopted.  Click to learn the difference between fire alarm codes and standards.

How do you know if your state or region is requiring 520Hz low frequency sounders?


The International Fire Code or IFC 2012 edition chapter 80 as well as the International Building Code or IBC 2012 edition chapter 35 both reference NFPA 72 2010.  With this said, you will need to find out if your jurisdiction has adopted the 2012 or newer version of the IBC or IFC code.  Better yet, System Sensor has provided a detailed map of the States and Regions currently adopting this code.  See below:

Map for 520 Hz Low Frequency Sounders