Purposefully Delayed Fire Alarm Notification

Recently, a number of inquiries were made to our office regarding the topic of delaying or preventing the activation of fire alarm notification appliances. In one case, an owner wanted to activate notification only after a second fire alarm was initiated, basically ignoring the first alarm for some period of time. In another case, an owner wanted to delay notification activation until after the responding fire department arrived so that they could determine if notification really needed to be activated.

At the heart of all of these inquiries was a lack of trust in the first alarm's truthfulness or reliability. However, setting that concern aside for the moment, it is a good time to review what code-approved options exist for the activation of notification appliances.

The National Fire Alarm and Signaling Code (NFPA 72 2016) contains all of the requirements for the activation for the large variety of notification appliances available today, including bells, horns, loudspeakers, lights (i.e., strobes), text displays or video displays. It also contains the requirements for when these notification appliances should be activated. The code allows for automatic notification, presignal notification, positive alarm sequence and detector cross-zoning as described below.

Automatic notification

The vast majority of fire alarm systems provide an immediate activation of fire alarm signals either to the entire facility (so-called general alarm) or selective parts thereof. This is in accordance with the requirements of section 10.11.1, which states that actuation of alarm notification appliances or emergency voice communications “shall occur within 10 seconds after the activation of an initiating device.” It also states that all types of notification appliances “shall be activated and deactivated as a group unless otherwise required by an ECS emergency response plan” (10.11.2). Thus, the default for all fire alarm systems is automatic alarm notification.

Further, the code requires that a subsequent actuation of another device “shall cause the notification appliances to reactivate” (10.12.5), again without any delay. Other than what is presented below, the code provides no other options for alarm notification activation, even with the approval of the authority having jurisdiction (AHJ).

Presignal notification

The requirements for presignal notification are in Section The use of this option requires the approval of the AHJ. The details of the presignal operation shall be provided in the shop drawing submittal as Section 7.4 requires. Occasionally, the use of additional documentation with the AHJ, like a memorandum of understanding or code variance, must be executed as well with presignal activation.

A presignal fire alarm system must initiate a fire alarm system at a constantly attended “central location,” like a “department office, control room, or fire brigade station.” The key to this requirement is that the location is “constantly attended” and thereby available to immediately take action (e.g., by an immediate dispatch of emergency response). Whether the “central location” is to a local or remote, even off-site, location, the fire alarm signal must be sent upon the initial (i.e., first) alarm signal. In approving such systems, the AHJ must take into account the time involved from alarm initiation to receipt by the “central location,” as well as the time for actual fire service response.

The actuation of notification appliances is allowed by two means: “(a) Human action that activates the general fire alarm; (b) A feature that allows the control equipment to delay the general alarm more than 1 minute after the start of the alarm processing.” In practicality, the presignal system allows a responding fire authority to investigate the alarm situation prior to activation of the notification appliances. In such a system, a fire alarm designer must provide a means, usually within the fire command center or central response point, to manually activate the notification appliance sequence, since all normal alarm initiating devices (like manual stations) do not provide automatic alarm notification activation. This manual activation point may require special signage, protection, or other features required by the authority having jurisdiction, like that shown in Figure 1 (above).

In approving a presignal system, the AHJ takes on significant responsibility in considering the potential delay in notification and evacuation. The code provides no time limit on the delay prior to the “human action” that is required to provide building evacuation. This is a serious matter, for as the National Fire Alarm and Signaling Code Handbook states, “Delaying the operation of the fire alarm system during a fire can have disastrous consequences.” Thus, approval of presignal systems are usually limited to specific occupancies that have localized and rapid response to emergencies, specific and defined emergency response procedures, and potentially large occupancies where occupants would be significantly affected, often adversely, to an evacuation alarm signal. Occupancies like airports, government facilities, and large entertainment or convention centers may be examples of locations that meet the needed requirements for presignal systems. Based on the risks involved with this potentially significantly delayed notification, use of presignal systems is extremely limited and subject to much scrutiny.

Also, it should be noted that presignal systems apply to an entire fire alarm system (control unit) whereby all devices are either automatic alarm or presignal. Subdivided areas or sections of a building, even if a separate smoke or fire zone, are not permitted to be presignal while remaining areas are automatic alarm. Such a selective use of presignal would be confusing to occupants and responding authorities and detrimental to emergency response.

Presignal notification should not be confused with the alarm verification feature permitted by The alarm verification feature only delays the alarm signal for 60 seconds or less and requires no human intervention; thus, it is not considered presignal notification as defined in the code. However, where presignal systems are approved for use, other code-approved delays, such as alarm verification, cross-zoning, and positive alarm sequence, are normally not allowed so as to prevent a lengthy delay process before responding authorities are alerted. The National Fire Alarm and Signaling Code Handbook states, “The intent of these Code paragraphs is not to permit multiple or compounded delays to be programmed into the system, thus further delaying occupant notification and fire department response.”

Positive alarm sequence

The requirements for positive alarm sequence notification are in The use of this option requires the approval of the AHJ. The details of the positive alarm sequence operation shall be detailed in the shop drawing submittal as required in 7.4. Chapter 24 allows positive alarm sequence to be used for in-building fire emergency voice/alarm communications systems.

Positive alarm sequence could be called a semidelayed means of alarm notification activation, because the alarm notification appliances will be activated automatically if the proper response is not received by the fire alarm control unit. Upon activation of a first initiating device, the signal must be acknowledged at the fire alarm control unit within 15 seconds, otherwise the notification appliance sequence will be activated. If properly acknowledged, trained response personnel have 180 seconds to investigate the alarm source and initiate a reset of the fire alarm control unit. If the system is not reset within this timeframe, or if a second alarm from a different device is received, the notification appliance sequence will be activated.

In approving a positive alarm sequence, the AHJ would take special note of the exact sequence to be used, judging it against the code's prescriptive requirements. It would be important to note where alarm initiation is annunciated, and thus acknowledged, because that is the first critical step in the process. The building’s emergency response plan would need to be in harmony with, and designed in conjunction with, the positive alarm sequence. Again, use of positive alarm sequence may be limited to specific types of occupancies or building uses and should only be implemented after a full analysis of the risks involved with the potential delay of notification activation. However, facilities such as those containing large production or assembly lines, occupied stadiums and arenas, professional theaters, medical operating rooms, and the like may be able to take advantage of the investigation time period prior to full activation of notification appliances.

The code language used allows positive alarm sequence to apply to only certain devices or subdivided sections of a building, or even allow it to be a programmed option that is activated and deactivated only for specific times by responsible authorities. For example, think of a large professional theater that is actively monitored by trained personnel during a theater performance. A specific performance may activate an initiating device due to performance related smoke, fog or lighting. Use of positive alarm sequence would allow the device activation to be investigated by control room and production personnel, thereby preventing an unnecessary evacuation or allowing activation for a programmed shutdown of the performance under a real alarm scenario. The same could be true for a medical operating room, with similar resultant benefits. It may be possible to provide positive alarm sequence while the theater or operating room is in active use, while providing normal non-delayed alarm response during unoccupied periods.

One additional note regarding positive alarm sequence: The code requires investigation of a fire condition to be done by “trained personnel” ( Currently, this term is not defined by NFPA 72 and, thus, may be open to some interpretation. However, personnel who are charged with investigating a "delayed" alarm should be thoroughly familiar with the facility, understand the programmed sequence, have the ability to distinguish specific fire alarm devices and what activates them, and be able to make an accurate, thorough decision regarding the emergency situation prior to providing the command to reset the system. That is a lot to ask of a person within three minutes, thus the requirement for training. The issue of the “trained personnel” at a facility will be one that needs to be fully explained to an AHJ to allow for a thorough review and approval of positive alarm sequence implementation.

Detector cross-zoning

Although rarely used for non-releasing fire alarm systems, cross-zoning of two automatic detectors is allowed by the code to delay notification activation. Sections and allow the operation of two automatic detectors as a pre-requisite of alarm response and notification activation under a very specific set of circumstances. There must be at least two automatic detectors in each protected space, the alarm verification feature cannot be used, and the spacing of the detectors must be effectively reduced by 30 percent, with “a linear spacing of not more than 0.7 times the linear spacing determined in accordance with Chapter 17.” In most cases, this makes a system cost-prohibitive to install, very difficult to program, and extremely difficult perform acceptance and periodic testing. As with the other options discussed herein, the AHJ must approve the use of detector cross-zoning.

Purposefully delayed fire alarm notification

It should be noted that the allowance of presignal, positive alarm sequence and cross-zoning as a differing notification sequence has nothing to do with a fire alarm system that has shown itself to be prone to nuisance alarms. These are options to be used to purposefully design specific emergency response procedures for specific occupancy types. These options are to be discussed and approved with your AHJ so that the most effective emergency response can be provided. If a system is proving to experience nuisance alarms, the answer is not to delay notification, but rather to fix the problem through a detailed engineering analysis. Similarly, if an owner wishes to not hear from their fire alarm system, the answer is to provide a more reliable fire alarm system rather than to delay required notification.

About the Author

Larry Rietz

Larry Rietz is a NICET Level IV certified fire alarm designer with over 22 years of life safety industry experience. After working for almost 14 years with a large fire alarm manufacturer and service provider, he is now director of the Denver office...

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