A fire alarm system uses a system of audible, visible, and/or voice alarms to ensure that building occupants are efficiently warned of an emergency. These notifications can take many forms and be used in different ways, depending on the best way to react to the emergency.
Fire alarm code requirements are driven by NFPA 101 and NFPA 72, but may vary depending on your location. Federal, state, and local authorities all have a role to play in creating guidelines for the proper notification appliances to use for various use cases. For example, some jurisdictions require that audible alarms or strobes be used in sleeping areas or shared-use spaces.
How do notification appliances work?
Notification appliances are devices that are wired into the notification appliance circuit and are controlled by the fire alarm control unit. These devices, which are strategically placed throughout the circuit to provide emergency notifications, function through the use of electrical currents and diodes. The appliance maintains a consistent supervisory voltage level that indicates normal conditions. When an emergency occurs, polarity is reduced within the notification appliance triggering notifications and alarms that are then deployed by the fire alarm control unit.
Types of notification appliances
When an emergency occurs, it is important that all building occupants can be properly warned so they can take steps to protect themselves and others. Unfortunately, deaf and hard-of-hearing people can’t be notified via an alarm, and visually impaired people can’t see a strobe alarm. That’s why your fire alarm control system should use multiple types of notification appliances to inform and warn occupants. Modern fire alarm control systems employ a combination of audible, graphical, visual, and even tactile alarm systems.
Audible notifications can take the form of voice messages, loud tones, or both. Horns can only generate a single tone or sound. Fire alarm speakers can be used to relay emergency messages, evacuation guidance, or alarm tones. A combination unit can be used that provides the speaker and a strobe light to alert and inform. These appliances are commonly mounted on the wall or the ceiling.
The NFPA provides guidelines for audible notifications, which must be within certain decibel ranges and tones.
While often used in conjunction with audible signals, visual signals are designed to capture the attention of building occupants even in the absence of an alarm. Some of the most common types of visual signals are text signals, such as illuminated fire escape warning lights and strobe lights. Strobe lights are among the most common visual signals in use, with bright lights and flashing serving as an early warning for building occupants. These lights can be found in hallways, stairwells, and common areas mounted to the ceiling or on the wall.
NFPA 72 provides guidance on the appropriate placement and brightness of such devices. For example, any strobe alarm used in your fire control system must be bright enough to be seen even if the occupant is not facing the alarm when it goes off.
Graphical signaling, which is sometimes referred to as textual notification, refers to the use of text or graphics, such as those on emergency exit signs.
Finally, for special circumstances, tactile signaling appliances can be used. For example, in a building with deaf and hard-of-hearing residents, a tactile signaling device can alert occupants to an emergency in different ways, such as through vibration.
Public vs. private mode signaling
Your fire safety notification system can be used in a variety of ways. For example, public mode signaling is appropriate in most buildings, while in other facilities, the alerts should first be delivered to emergency response personnel.
Public mode signaling
Public mode signaling is used when an emergency requires urgent notification for all building occupants. The purpose of public mode signaling is to notify all building occupants so that they can take independent action to evacuate. This is the most common type of emergency signaling system.
Private mode signaling
Private mode signaling is used to communicate directly with those responsible for responding to the emergency, such as when a building has its own emergency response teams. This type of signaling is often used in areas where the occupants cannot take independent action to evacuate, such as incarceration centers and hospitals, or long-term care facilities. When the private mode signal is triggered, it directly informs those responsible for initiating and coordinating evacuation efforts.
Private mode can be used in such buildings to avoid creating panic and confusion and give staff time to initiate an orderly response. This mitigates the possibility of unauthorized action and ensures that emergency plans are followed appropriately.
Apart from all of the notification types, there are also different notification strategies. While most of the time, using a public mode signaling strategy that alerts all occupants at once works best, some buildings deliver their notifications via pre-set zones.
Imagine a high-rise building with a complex series of fire stop and suppression systems, numerous ways to exit the building, and multiple elevators and stairwells. This situation may call for a zoned notification scheme. With zoned notification, you can prioritize and sequence your alarms to ensure that occupants can evacuate quickly and safely. For example, a fire on one floor may present the most serious and urgent danger to the residents on the next floor, so your strategy would be to evacuate those in greatest danger first.
What is most important in determining the correct devices and strategies to use in your building’s fire alarm system is that you can quickly alert and motivate occupants to take appropriate action. That’s why many large buildings also use technology such as social media or SMS text messaging to push instructions and guidance to building occupants when an emergency occurs.