When, how to tailor occupant notification for varied settings

Learn the innovative strategies for building safety, from private signaling to positive alarm sequences

By Consulting-Specifying Engineer February 6, 2024
Fire alarm control units aid in compliance with NFPA 72. Courtesy: Anna Steingruber, CFE Media and Technology

Occupant notification insights

  • Full building notification is the common approach, but situations like high-rise buildings may require partial notification.
  • Private mode signaling is suitable for specific scenarios like hospitals and pre-signal features involve transmitting signals to a constantly attended location before buildingwide notification.
  • Positive alarm sequence allows for a temporary delay and investigation, while alarm verification is a smoke detector feature to reduce unwanted alarms with a specified delay before notification.
  • Learn to examine fire alarm notification objectives, along with occupant behavior patterns in emergencies, to determine the best design for achieving system goals.

The text discusses various occupant notification strategies in the context of building safety, such as full building notification, partial/selective notification, private mode signaling, pre-signal features, positive alarm sequence and alarm verification. Read the transcript of this webcast, and watch the on-demand event here. This transcript has been edited for length and clarity.

Presenter: Chris Campbell, PE, Principal & Founder, Campbell Code Consulting, Elkridge, Maryland.

There are several occupant notification strategies that can be found in the building codes and in NFPA 72: National Fire Alarm and Signaling Code. First off, we have full building notification. This is the most common approach to occupant notification. This is when the fire alarm system activates, all areas of the building are notified simultaneously, and this generally results in full building evacuation. This is the simplest approach from a design and a programming standpoint.

However, there are situations where full building notification is maybe not the best strategy. For example, consider a high-rise building. A high-rise building is a situation where you may not want to do full building notification, particularly if that is going to result in the simultaneous evacuation of thousands of occupants.

Fortunately, the code does have provisions for a situation like that, and that leads us to a partial or selective notification. This is a strategy where only certain areas of the building are notified upon activation of the fire alarm system. For example, in the IBC, in a high-rise building, the code specifically permits the fire floor plus the floor above and below to be notified upon activation of the fire alarm system. In some jurisdictions, you may see the fire floor and two floors above and two floors below be part of the strategy.

With this partial notification strategy, it is just those floors that are receiving the notification upon activation of the system and those occupants would then presumably begin their evacuation or potentially relocation in the building.

There are situations where you may have separate notification zones on a single floor. For example, a building that has a very large footprint, so let us say a casino for example that may be a situation where you have separate notification zones on a given floor so that occupants that are very distant or remote from the fire event are not notified initially. If you are taking that strategy, that is something you would want to coordinate and get approval from the AHJ.

Next up we have private mode signaling. We mentioned this a little bit earlier in the presentation. Private mode signaling is a strategy where only persons that are directly involved with the implementation of an emergency response plan are notified. A great example of this would be in a hospital setting. For example, consider an emergency department where the private signaling approach is that the notification occurs only at the nurses’ station, and then the staff that is at that station would be responsible for beginning to implement whatever is the planned response procedure. This is specifically permitted in groups I and M. It also is allowed in NFPA 101 where occupants are incapable of evacuating themselves due to age, physical or some type of disability.

Pre-signal occupant notification

Next up we have a pre-signal feature. A pre-signal feature is not going to be widely used, but it is an approach where upon activation of a fire alarm initiating device, the signal is initially transmitted only to some constantly attended location. The idea is that at that constantly attended location, there is a local fire brigade, or perhaps it is a municipal fire department, where there are qualified personnel who can immediately begin investigating and responding to the situation. While that initial response is occurring, there is no notification that occurs in the facility and it is only upon manual activation by those qualified personnel that the building is notified.

Obviously, this is not an approach that is appropriate for all facilities. You need to have qualified personnel who are always available to respond to implement something like this. The IBC does reference the pre-signal feature, but it does specifically require approval by an AHJ. NFPA 101 does allow pre-signal in some existing occupancy chapters, but it is not permitted in any of the new occupancy chapters. This is not a widely used feature and it is really a select grouping of facilities that could potentially use a pre-signal feature.

Next up we have the positive alarm sequence. Step one in a positive alarm sequence is the activation of a detection device. Upon that activation, a signal is going to occur at the fire alarm control unit. Once that signal occurs at the fire alarm control unit (FACU), there is a 15-second period where it must be acknowledged by qualified personnel. If the signal is not acknowledged at the FACU within 15 seconds, then building notification would occur. If the signal is acknowledged within 15 seconds, then that is going to begin an alarm investigation phase of up to 180 seconds during which you are going to conduct some sort of evaluation by these qualified personnel to determine the fire threat.

Within that 180-second period if the qualified personnel resets the system, then no building notification would occur, but if the system is not reset within 180 seconds, or if a second detection device activates within that 180-second period, then building notification would occur. Positive alarm sequence is a temporary delay and notification to allow for some level of investigation of the threat. Positive alarm sequence is not directly referenced in the IBC, but it is referenced in NFPA 101 and there is a section in NFPA 72 with a list of requirements if you choose to implement a positive alarm sequence.

Then finally we have alarm verification. This is a feature for smoke detectors to reduce unwanted alarms. If there is a smoke detector that has been programmed with an alarm verification feature, upon initial activation of that detector, the detector or the programming of the fire alarm control unit is going to reset that detector and wait for a specified period up to one minute. Then it is only after that specified period that a valid alarm signal would be accepted.

If the initial activation occurs, the detector resets itself, waits one minute, if after that one minute there is no alarm signal coming from the detector, then nothing further would occur, but if after that minute there is still an alarm signal coming from the detector, then the FACU would accept that alarm initiation signal and then begin with notification. This feature is only intended to be used where there are transient occupant conditions. It is not intended to compensate for poor design, and technically this is not a notification strategy. Rather it is just a delay in accepting an alarm signal which thereby results in a delay in notification.