NFPA 72: Overview of National Fire Alarm and Signaling Code (Chapters 15-23)

By Justin Sagalow

November 16, 2022

While the National Fire Protection Association, or NFPA, does us all an invaluable service by providing robust safety standards, they don’t always make accessing these codes especially convenient. Currently, there are only two ways to review the 2022 edition of the NFPA 72 National Fire Alarm and Signaling Code on the NFPA website.


You can either subscribe to their premium subscription service, NFPA LiNK, which can run you anywhere from approximately $10-40 a month depending on the plan you select, or access a free version of the PDF, which is little more than a scan of the physical document and doesn’t allow for searching. Always striving to demystify the world of fire alarm systems, we started this series of articles to help you locate the section of the code most relevant to your questions.

Picking up where we left off last time, let’s continue our review of the NFPA 72 National Fire Alarm and Signaling Code. The NFPA standards, most recently updated this year, establish the requirements for automatic fire detection and fire protection systems and exist for everyone’s safety and protection. If you are looking for more detail on any one topic or have any questions, please feel free to call toll-free here at Digitize to speak with an engineer.

Chapters 15-16: Reserved (for future use)

The title of this article, purposely chosen to maintain consistency with the previous two entries in this series, is a bit of a misnomer. Chapters 15 and 16 are both reserved for future use, much like Chapters 4-6 and Chapter 13.

As we’ve clarified in the previous NFPA overview articles, the authors of the NFPA fire codes occasionally leave chapters empty in case they decide to add additional information in the future and do not want to unnecessarily disturb the existing order of the following chapters.

Chapter 17: Initiating Devices

smoke detector, heat detector, and pull handle

In this image, we see a smoke detector, heat detector and pull handle. These are "initiating device" subcomponents of a fire monitoring system.

Chapter 17 is concerned with the application, purpose, and general requirements for the various types of initiating devices. 17.2, the section in which the NFPA outlines the purpose of initiating devices, also functions as a sufficient practical definition of initiating devices, stating:

“Automatic and manual initiating devices shall contribute to life safety, fire protection, and property conservation by providing a reliable means to signal other equipment arranged to monitor the initiating devices and to initiate a response to those signals.”

Section 17.3 addresses the “performance-based designs” of new initiating device models. It states that any new design must be submitted to the authority having jurisdiction for review and approval. The performance objective that the model seeks to accomplish with its new design must be clearly stated and substantiated with proper documentation in an approved format.

Sections 17.6-17.17 cover the most common types of fire and life safety initiation devices, their unique properties, and the standards they must adhere to in regards to their construction and operation. In these sections, the NFPA outlines the differences between heat, smoke, and energy-sensing detectors, carbon monoxide detectors, and initiating devices for local extinguishing systems, like sprinklers.

In each section, the NFPA expresses the need for standards such as universal marking, color-coding, and placement within a room. For example, one section states that manual fire alarm boxes should be red in color, conspicuous and accessible in placement, and located within 5 feet of exit doorways. Previously on this site, we have reviewed the commonly accepted definition for initiating devices, along with the many kinds that exist on the market and the manufacturers that most famously produce them.

Chapter 18: Notification Appliances

smoke detector table

This is an image of a generic smoke detector. This is an example of an initiating device and notification device, as it detects smoke and produces a loud noise, but does not contact a municipal fire department or emergency service.

Similar in form to Chapter 17, Chapter 18 reviews the application, purpose, and audible and visual characteristics of common fire alarm system notification appliances.

Noteworthy perhaps is that, in 18.3, the section regarding physical construction, the code states that notification appliances used for signaling anything other than fire shall not have the word fire, or any fire symbol, in any form on the appliance visible to the public. Notification applications with multiple functions, including the notification of a fire, can have fire markings, but only on those visible elements used for fire signaling.

Sections 18.4-18.9, the sections dedicated to the audible and visual characteristics of notification appliances, explicitly dictate the minimum and maximum volume level of alerts produced by notification appliances, along with the duration of the sound used to measure these volume levels.

The standards for the visual characteristics of notification appliances are painstakingly detailed, going as far as to dictate that characters, which should contrast with their background, should also have a non-glare finish and conventional, non-decorative fonts. The spacing between individual characters should be “minimum 10 percent and maximum 35 percent of character height.”

In any selected font, the width of the uppercase letter “O” should be “55 percent minimum and 110 percent maximum of the height of the uppercase letter “I".” The stroke thickness of the uppercase letter “I” is also required to “be minimum 10 percent and maximum 30 perfect of the height of the character.”

As you can see, these standards are quite comprehensive. If you would like to learn more about the various requirements for the audio and text on notification appliances, we recommend reviewing this section in full for yourself.

Chapter 19-20: Reserved

These chapters are reserved for future use.

Chapter 21: Emergency Control Function Interfaces

Emergency control function interfaces enable fire alarm systems to interact with emergency communication systems and other life safety systems located within the building during an active fire alarm. Chapter 21 is concerned with the installation and operation of emergency control function interfaces in buildings. For example, the NFPA requires that emergency control functions are able to be performed automatically, but that the performance of these functions does not interfere with power intended for providing lighting throughout the building or operating elevators within the building.

Section 21.2 makes a point to specify that the method of interconnection between the emergency control function interface device and the component controlling the emergency control function should be either “electrical contacts listed for the connected load or data communications over a signaling line circuit dedicated to the fire alarm or shared with other premises operation systems, along with other listed methods.”

Sections 21.3-21.11 pertain to emergency functions interfaces. This includes the the systems responsible for elevator emergency recall and shutdown, the presence of smoke and heat detectors in HVAC systems, and the interfaces that control fans, electrically locked doors, and exit marking audible notification systems.

If you feel that the information in this chapter may pertain to you or a question you have in regards to your fire alarm system, we recommend reviewing this section in full for yourself, as we do with every chapter of the NFPA 72 National Fire Alarm and Signaling Code.

Chapter 22: Reserved

This chapter is reserved for future use.

Chapter 23: Protected Premises Alarm and Signaling Systems

This chapter, the last in today’s edition of this series, revolves around the NFPA requirements for the application, installation and performance of alarm and signaling systems. These systems are defined by the NFPA in this chapter as systems “for the protection of life or property, or both, by indicating the existence of heat, fire, smoke, carbon monoxide, or other emergencies impacting the protected premises.”

In section 23.2, the NFPA addresses the topic of cross-system compatibility in newer, computer-aided alarm systems by stating that “software and firmware within the alarm and signaling system that interfaces to other required software or firmware shall be functionally compatible.”

In section 23.3, the section titled “System Features,” the NFPA declares that “the features required for a protected premises fire alarm system shall be documented as a part of the system design.” The following subsections outline that these “features” are based on the requirements of “other applicable codes or statutes” determined by the authority having jurisdiction, similar to the performance-based designs in section 17.3.

Similar also to section 17.3 is the content explored in subsection 23.3.2, which is concerned with nonrequired systems and components. Echoing the requirements of performance based designs, here, the NFPA states that the features of these voluntary systems must be “established by the system designer on the basis of the goals and objectives intended by the system owner.”

Sections 23.4-23.7 address the performance of various circuits and components of alarm and signaling systems. This includes initiating device and signaling line circuits. For the class designations assigned to these circuits, this chapter refers to the information provided in Chapter 12. In subsection 23.6.2, The NFPA requires that no area should be served “solely by a single device where Class N pathways are deployed, such that a single device failure resulting from a multiple ground-fault pathway failure would render an area or zone incapable of initiating input signals or receiving output signals.”

The NFPA’s preoccupation with a single point of failure bringing a greater area’s fire alarm system offline is reinforced in subsection This subsection states that “Class N pathways shall not be accessible to the general public or building occupants for any purpose other than specified in the network design analysis, maintenance, and deployment plans.” The NFPA’s concern over this is for good reason. After all, we’ve witnessed it ourselves.

prism lx central display screen

This is an image of a Prism LX central display screen. For those who wish to monitor their fire monitoring system instead of hiring a third party service to do it, the prism lx is one example of a readily available server on the market.

Confused? Give us a call to discuss NFPA 72

That concludes this portion of our review of the 2022 edition of the NFPA 72 National Fire Alarm and Signaling Code.

Adhering to the NFPA 72 National Fire Alarm and Signaling Code is not optional. This document was carefully designed and put in place for everyone’s protection.

Understanding the Code may not be easy, but no one said that you have to do it alone. One quick call with an expert at Digitize can make all the difference. Give Digitize a call at 1-800-523-7232. You can also send email to We'll help you get your project off on the right foot.

Justin Sagalow

Justin Sagalow

Justin Sagalow is quite uniquely qualified for his Marketing Writer Position at Digitize. Arriving at Digitize with experience in law, finance, and editorial positions, Justin's skillset allow him to effectively communicate how best Digitize can address each client's individual needs. From his...Read More