nfpa 72 chapters is organized into chapters, each relating to a different topic and several annexes that contain supplemental information. The contents are organized into four main categories:

• The Administrative chapters use the “ones.” Chapters 1 through 9.
• The Support chapters use the “teens,” Chapters 10 through 19.
• The System chapters use the “twenties,“ Chapters 20 through 29.
• The code also has Usability Annexes A through G.

In order to create and  maintain this grouping, the code does not actually use all 29 nfpa 72 chapters numbers. In fact, only 15 are  currently used. Unused chapters are identified as ”reserved”.

The content in the support chapters has the information about what makes a system do something or how to ensure that the system is operational and meets the designer’s goals. These are the components used to build and maintain systems.

The key subjects of NFPA 72 are the Protected Premises Fire Alarm Systems covered by Chapter 23 and Single-and Multiple-Station Alarms and Household Fire Alarm Systems covered by Chapter 29. These two types of systems are the most common areas where NFPA72 is referenced and used.

Chapters 26, Supervising Station Alarm Systems, and 27. Public Emergency Alarm Reporting Systems, address the transmission of signals off-premises. These systems are used to initiate the response of emergency forces as well as service and maintenance organizations.

Annexes are not a required part of and NFPA code or standard, but are supplementary. Annex A is used to provide examples and additional text to explain requirements within the body of the Code.Annex B is an Engineering Guide that contains methods to calculate system parameters