NFPA 72 Overview, Chapter 18: Notification Appliances

After our previous discussion on NFPA 72 Chapter 17: Initiating Devices, let's continue with the next chapter:

"Notification appliances" are the devices that let building occupants know about the existence of a fire and how to properly respond to it. Mostly, this means giving evacuation instructions.

This general summary is reflected within NFPA 72 as follows:

18.1.3 The performance, location, and mounting of notification appliances used to initiate or direct evacuation or relocation of the occupants, or for providing information to occupants or staff, shall comply with this chapter.

This is the essential scope of Chapter 18. Obviously, there are many more details to go over, so let's dig in!

Listing by an approved lab is always required

UL or ETL or similar listing is required for any notification appliance, just as it is for all other critical fire alarm systems:

18.3.1 Listing. All notification appliances installed in conformity with Chapter 18 shall be listed for the purpose for which they are used.

Notification appliances must be built to survive their specific installation environments

Requirements for resistance to destructive forces will vary based on where you plan to install notification appliances. Section 18.3.3.1 demands that properly listed equipment be used for the following types of areas:

• Outdoors
• Indoors
• High temperatures
• Low temperatures
• High humidity
• Dusty conditions
• Hazardous locations
• Areas subject to tampering

At Digitize, our manufacturing experience stems from our corporate family of companies. Based on that background, we know quite a bit about engineering for harsh environments. Our equipment is often available in different build variants that are suited for different environments.

As one example, we commonly have gear that is rated to temperatures just below the freezing point of water (0 degrees C or 32 degrees F). When required, we'll swap out a handful of sensitive components for more rugged options. That can deliver a device that can handle temperature down to -40 C (which is also -40 F).

When you're seeking notification appliances for use in a specific location, be sure to choose something that's built for and listed for the appropriate environment.

18.3.7 Notification Appliance Circuits

This is a short section that I found interesting for a specific reason. It is simply a reference to Chapter 12 and Chapter 14, which collectively dictate circuit requirements and wire size requirements. These are clearly relevant to the reliable operation of notification appliances, so this section serves as a simple external reference to the fact that you must also comply with those other sections of NFPA 72.

18.4.1.2 (Max 110 dBA)

This is something I didn't expect to see, but the code does have to cover all aspects, I suppose. It's in this section that we actually find a MAXIMUM sound level permitted for notification appliances. I'm sure this is based on science that balances the obvious need for prompt and noticeable notification with the contrasting goal of not causing hearing damage:

18.4.1.2* The total sound pressure level produced by combining the ambient sound pressure level with all audible notification appliances operating shall not exceed 110 dbA at the minimum hearing distance.

Interestingly, the sound level inherent to the location at all times is also a factor here. If you have anything other than a nominal sound level in your environment, this is something you'll have to take into account when purchasing and installing notification devices.

18.4.2 Distinctive Evacuation Signal

In this section, NFPA 72 describes the sounds that audible notification appliances must make when instructing people to either exit the building or move to a safer area. I did not realize until I read through this section of fire code that alarms were dictated anywhere near this specifically.

As I think about the handful of times I've heard a fire alarm in a public place, I can clearly recall what the code describes. NFPA 72 requires:

"(Alarm signals) shall be the standard alarm evacuation signal consisting of a three-pulse temporal pattern in accordance with ANSI/ASA S3.41..."

18.4.3 Distinctive Carbon Monoxide Audible Alarm Signal

This section is incredibly similar to the previous, except that it describes how a CO alarm must sound.

The code acknowledges that a CO alarm may not need to make a sound, but that it must be a four-pulse sound if one is used. This obviously makes it possible for those in the know to tell the difference. For the average building occupant, a series of loud rapid beeps will simply be a signal to evacuate.

18.4.4 Public Mode Audible Requirements

This section describes how public-address audio must be 15 dB above the average ambient sound level in the environment (or 5 dB for anything that lasts longer than a minute). That's logical, since anything that doesn't climb above ambient noise floor is going to be very difficult to understand. The required differential also compensates for what may be a heightened level of crowd noise during a fire emergency.

Placement of Notification Appliances

The remainder of Chapter 18 of NFPA 72 focuses largely on the specific placement requirements for notification appliances. This varies heavily depending on the section of your building (ex. sleeping areas vs. public areas).

Much like we saw in earlier chapters, there are actually reference tables describing how much spacing is allowed based on factors like ceiling height. If visual appliances are higher, they need to be denser to maintain adequate coverage. The same thing was true about smoke detectors and other initiating devices when covering medium and large rooms.

Along these same lines, specific placement of appliances dictates how big their lettering must be. Signs like the common green "EXIT" sign must be readable to be effective, so the fire code dictates how big is big enough for most readers.

Call Digitize for Additional Information about Fire Code Requirements

We're a manufacturer of fire alarm monitoring systems at Digitize, so we know a few things about the fire code. In all cases, we'll refer you to the current edition of NFPA 72 for the final word on any concept.

What you'll find when you call us, however, is that a little bit of initial guidance from an engineer with experience goes a long way when you're just getting started.

To get help with your project, call Digitize at 1-800-523-7232 or email info@digitize-inc.com