Which of the following may initiate a fire alarm system? I . A manual fire alarm II . An automatic detector III . An extinguishing system

A fire alarm system is initiated by a signal from an "initiating device." According to NFPA 72, an initiating device is a component that originates a change-of-state signal in response to a stimulus. This definition encompasses all three listed items:

I. A manual fire alarm box (pull station) allows for human intervention.

II. An automatic detector senses products of combustion like smoke or heat.

III. An extinguishing system, such as a sprinkler system, uses a waterflow switch to send a signal to the fire alarm control unit upon activation.

Therefore, all three are valid methods for initiating a fire alarm.

A. I and II: This option is incorrect because it omits the activation of the alarm by an extinguishing system, which is a common initiating method.

B. I and III: This option is incorrect because it omits automatic detectors, which are a primary means of fire alarm initiation.

D. II and III: This option is incorrect because it omits manual fire alarm boxes, a fundamental and required component of many alarm systems.

1. NFPA 72®, National Fire Alarm and Signaling Code, 2022 Edition.

Section 3.3.157 Initiating Device: Defines an initiating device as "A system component that originates a change-of-state signal in response to a stimulus."

Annex A.3.3.157: Provides examples of initiating devices, explicitly stating, "An initiating device can be a manually operated switch (e.g., a manual fire alarm box), a sensor (e.g., a smoke detector), or a switch that is operated by a change in condition (e.g., a waterflow switch)." This directly supports all three options.

2. NFPA 921, Guide for Fire and Explosion Investigations, 2021 Edition.

Section 6.4.2 Fire Detection Systems: Discusses how these systems are initiated by both manual alarm boxes (6.4.2.1) and automatic detectors (6.4.2.2).

Section 6.4.3.1 Sprinkler Systems: States that "When a sprinkler activates, a waterflow switch detects the flow of water and transmits an alarm signal."

3. Icove, D. J., & Haynes, G. A. (2018). Kirk's Fire Investigation (8th ed.). Pearson.

Chapter 14, Fire Detection and Alarm Systems: This chapter details the various components of alarm systems, describing manual pull stations, automatic detectors (heat, smoke, flame), and waterflow switches from suppression systems as primary types of initiating devices. (p. 468-474).