For most people, the first time they hear a fire alarm is during a drill. Afterward, in some cases, they might be surprised (and perhaps a bit dismayed) to learn that those alarms didn’t go off throughout the entire building as they might have assumed. This could have occurred due to a functional problem with the alarm, which would, of course, be cause for great concern. However, in the vast majority of cases, when a fire alarm does not operate the way a person might expect, it is operating exactly as intended based on the structure of the building and its use, which in terms of fire code, is known as its “occupancy.”
There are many different situations described in the National Fire Protection Association (NFPA) 101 Life Safety Code that call for alarms to selectively sound in certain areas of a building. And, there are also situations that call for visible-only alarms as opposed to the blaring alarms most of us expect. This post will explore the scenarios that call for different approaches to how fire alarms might operate in your building and the rationale behind them.
Interesting Exceptions to the “Everybody Out” Alarm
The requirements for how fire alarms are required to operate are provided in the NFPA 101 Life Safety Code. Notification requirements – how the people inside the building are alerted to a fire emergency – depends in part on the occupancy of the building or area within a building the alarm system is intended to protect. Depending on the occupancy:
- Not all fire alarms will make a sound. Some may be visible-only alarms.
- Fire alarms may not always sound in all locations in the building at the same time.
- Fire alarms may notify only those responsible for implementing emergency procedures as opposed to everyone in the building.
While these facts may seem contrary to the way most people might think of how a fire alarm should operate, there are good reasons behind them.
Audible and Visible Alarms
Most alarm systems are required to include both audible and visible signals, particularly in new buildings. (Alarm systems in existing buildings are generally not required to be retrofitted with visible signals if they don’t already have them.)
For most buildings, with the exception of stairwells and elevators, the general evacuation alarm (the “everybody out” alarm) must sound throughout the entire building. However, there are exceptions to this.
A general evacuation alarm is not required for buildings or areas within them where occupants are incapable of evacuating themselves because of age, physical or mental disabilities, or physical restraint. This includes health care facilities, daycare facilities, jails, and prisons.
For these occupancies, the alarms must instead transmit an audible or visible signal only to those people responsible for implementing emergency procedures within the area or building in which the emergency is occurring. And, the signal must have the means to readily identify the zone, area, floor, or building in need of evacuation. This is known as “private operating mode” – and the reasons for using it in these settings are based on safety.
In settings where people cannot evacuate themselves due to physical or mental inability or incarceration, a loud alarm would create panic, making it more difficult for the people responsible for the occupants’ safety to conduct an orderly and safe evacuation. And, in hospitals, for example, where there are surgeries in progress and people in intensive or critical care recovering from a heart attack, sounding a 65-120 decibel alarm could be life-threatening as opposed to life-saving.
Zoned Alarm Systems
In cases where the configuration of a building makes complete evacuation all at once impractical, the Life Safety Code allows and in some cases, requires zoned evacuation, which in turn requires a different approach to occupant notification in emergency situations. In buildings with zoned evacuation plans, specific areas are defined to reduce the possibility of panic and provide for an orderly evacuation. In a building with a zoned evacuation plan, occupants in the affected areas are notified first to get them out of harm’s way, followed by alarms in other areas to complete the evacuation.
This type of arrangement is common for malls and most high rise buildings where people flooding into the stairwells from every floor at the same time would prevent those on the higher floors from escaping a fire that might be occurring several stories up. In these cases, the alarm would sound first on the fire floor and those immediately above and below to keep the stairways below clear for evacuation. Then, generally the subsequent alarms would sound as the fire or smoke spreads to floors above or below the initial alarm.
The need for zoned protection in high rise buildings is also one of the reasons audible alarms are not required in stairways. If there were alarms in the stairwells, people sitting near stairwell exits would be able to hear the alarms regardless of where they are occurring. This could create confusion as to why the alarm is not going off on their floor. Such confusion might cause people to evacuate too soon, possibly slowing the evacuation of occupants from the floors above, or lead people to assume that the alarm is not working properly, which can delay their response when and if the alarm sounds on their floor.
Understanding Your Fire Alarm System is Key to Fire Safety
Knowing the notification requirements for your fire alarm system, as well as, communicating that to the occupants of your building is critical to knowing whether or not it is working properly. Practicing regular fire drills and holding regular meetings to convey safety information is also important to the safety of your occupants. Understanding the occupancy of your building will give you some insight into how your system should function. However, fire alarm system requirements are complex both in terms of the different types of notification that may be needed and the system design requirements necessary to facilitate them.
Consulting with Koorsen's fire alarm experts will ensure your fire alarms comply with all the regulations and that they will function properly to help get the people in your building safely out of harm’s way in the event of a fire. Our certified technicians stay up to date on all fire safety regulations and evolving technologies. If you have questions or concerns about your fire alarm systems, Koorsen can help. Talk to a Koorsen expert today.
