Fire Alarm

(FACU) Fire Alarm Control Unit

A fire alarm system’s chief purpose is to detect fires and quickly notify both the occupants of the building and emergency services from a centrally controlled and monitored location. These systems also monitor themselves, identifying the location and origin of the alarms and sensing problems with connections and wiring that might prevent the system from working properly. Essentially, fire detection systems have four primary functions.

• Detection
• Alerts
• Monitoring
• Controlling

These highly advanced systems use a network of appliances, devices and control panels to perform these four functions. To help you better understand the workings of an alarm system, we’ll discuss each component in detail below. 

A fire alarm system consists of many components, including:

• Fire alarm control panel
• Initiation devices
• Pull stations
• Smoke detectors
• Duct detectors
• Heat detectors
• Beam detectors
• Air aspirating or air sampling smoke detectors
• Water flow switches
• Tamper switches
• Notification devices
• Audible devices
• Strobes
• Strobes/Horns
• Dialers or communicators
• NAC power supplies

Below we’re going to explain what each component does.

The fire alarm control panel, commonly abbreviated as FACU, is the system’s “brain.” It receives messages from the initiating devices, also known as inputs, and performs the following functions.

• Turning on notifications: Upon receiving signals from the inputs, the FACU will turn on the necessary notification devices, also known as outputs. It alerts people in the vicinity that an issue has occurred.
• Elevator recall: The FACU also recalls elevators, which eliminates the possibility of an elevator delivering people to a flame- or smoke-filled area. 
• HVAC system shutdown: If they detect smoke in an air duct, many fire alarm systems will shut the air handling unit down, thus preventing smoke from spreading to other parts of the building. 
• Notifying alarm monitoring center: The FACU will also alert a remote alarm monitoring station, which, in turn, will notify emergency services. 

A poorly designed or installed fire alarm system that doesn’t get routine maintenance, testing and inspection will likely go off even when there’s no genuine danger. Frequent false alarms will cause people to take them less seriously. When hearing a fire alarm, many people assume it’s no cause for concern unless they also smell smoke or see flames.

To minimize the incidence of false alarms, the fire alarm industry has pushed for proper system design, installation, testing, maintenance and inspection. 

The types of fire alarm systems include addressable and non-addressable.

• Addressable: Addressable panels monitor all alarm components individually. Each device comes with a distinct, separate address, which allows the panel to know their status, such as whether it’s functioning normally, in alarm or in trouble. For instance, addressable systems allow those working at a hotel’s front desk to know the exact location of the event by looking at the alarm panel display. 
• Non-addressable: This type of system puts all initiating devices in zones, meaning users physically have to check each device in that zone to find the one in alarm. For instance, if you have a non-addressable system and the alarm goes off, it would tell you something like “Alarm Zone 3, Fourth Floor.” 

Most property owners and managers prefer addressable systems, as they let you know the specific location of the alarm and assess the situation much more quickly. Some fire alarm panels can also notify remote alarm monitoring stations, which can then contact emergency services. Most state laws do not allow the panels to directly contact fire departments.

Fire alarm panels continuously monitor and indicate the state of the fire alarm system. For the majority of systems, there are three possible states. 

• Normal: “Normal” means that all appliances, devices, circuitry and wiring are functioning correctly and that there are no active alarms. 
• Alarm: This status indicates an active alarm.
• Trouble: If an open or short wiring develops in the circuits that connect the initiating devices and the fire alarm panel, or if the system’s phone line connection isn’t working, the system will go into a “trouble” state, which the control panel will display.

Initiation devices initiate alarms, and, just like alarm panels, they can be either addressable or non-addressable. Some initiation devices, like water flow switches, are traditionally non-addressable, but connect with addressable modules. The switches can have specific addresses that let them communicate with addressable systems.  There are many types of initiation devices. 

In addition to water flow switches, initiation devices can also be:

• Pull stations
• Duct detectors
• Smoke detectors
• Beam detectors
• Heat detectors
• Tamper switches
• Air aspirating detectors 

A pull station is probably the fire alarm system component you’re most familiar with. It’s a manually operated device that initiates an alarm signal when someone pulls its handle. While smoke may take a few minutes to reach a smoke detector, you can activate a pull station within just a few seconds of a fire or other emergency, which allows for a quicker evacuation and faster reaction times by the fire department. Pull stations are available in various sizes and shapes and can come with protective covers upon request. 

A smoke detector is a device that initiates an alarm signal when it senses smoke. There are two classifications of these devices, depending on the type of sensor they use to detect smoke particles. 

• Ionization detectors: These detectors contain tiny traces of radioactive material between two electrically charged plates. Ions flow between these two charged plates, but smoke particles disrupt this. If this happens, the smoke detector goes off. 
• Photoelectric detectors: Photoelectric detectors emit LED light beams in their detection chamber. When smoke particles come into this chamber, they scatter the beam of light, deflecting part of it on the detector’s photoelectric sensor. When the sensor detects this light, the alarm goes off. 

Duct detectors are smoke detectors installed in air conditioning and heating ducts. They shut air handling units down, preventing smoke from traveling all over the building via the air ducts. 

Heat detectors are fire detection devices equipped with sensors that respond to heat. Two main kinds of heat detectors are available.

• Rate-of-rise heat detectors: This type of heat detector will respond if the temperature increases at a rate that exceeds a specified value. 
• Fixed temperature heat detectors: Fixed temperature heat detectors will respond when their operating elements reach or exceed a predetermined temperature. There are two types of fixed temperature detectors: linear detectors, which monitor the temperature throughout an area, and spot detectors, which monitor the temperature in one specific location.

This kind of smoke detector projects a beam of light across the area it’s protecting. If smoke crosses the path of the beam, the detector will respond. 

This type of detector uses tubes to deliver air or smoke to a central detector equipped with a sensor that can detect minute changes to the air’s chemical composition. These detectors are usually highly sensitive.

Water flow switches use paddles located inside water-filled piping that will respond if water flows. On sprinkler systems, their design allows them to work if water is flowing from only one sprinkler. 

A tamper switch is a supervisory initiating device that operates if someone moves its valve from its regular position. 

These devices send a visual or audible notification to alert a building’s occupants to evacuate. 

Audible devices include sirens, bells and horns.

Strobes send notifications by flashing a light. 

These devices send notifications by flashing a light and blaring a siren to alert people to respond. 

Some fire alarm systems have internal or external dialers used to contact monitoring centers or alarm receiving stations. Communicators can use radio signals, phone lines or an internet connection to maintain contact. Panels may have built-in dialers or communicators. 

Today’s systems require many notification devices, which need extra power supplies, known as notification power supplies, or NAC power supplies. You can find these by the main panel or distributed around the building as needed.