FIRE ALARM SYSTEMS

Unlike sprinkler systems, which act to suppress a fire, a fire alarm system serves to detect the fire and evacuate the premises. Automatic devices, such as smoke and heat detectors, sense the fire and in turn trigger audio-visual devices. These audio-visual devices, such as horns, speakers, and strobes, act to notify the occupants of a building of an emergency situation. Manual pull stations also activate the audio-visuals, but rely on a person to operate them.
A fire alarm system is typically composed of a number of components. The control panel, which is the brains of the system, processes the inputs from the field devices such as the smoke detectors, and triggers the audio-visual units when it has determined that an alarm condition is warranted. There is a standby power supply, which consists of a battery charger and a set of batteries, that is sized specifically for each particular panel’s current load. If the building power were out, the batteries would keep the system operational for a predetermined amount of time. An annunciator panel, that is located in the front lobby of the building, tells emergency personnel exactly what type of alarm and where it has occurred (ie-3rd floor west wing smoke detector). There are silence and reset switches here as well that give operators control over the system. Lastly, a series of field devices that make up the initiating zones (smokes, heats, pulls, etc.), and notification appliances (horns, speakers, strobes), for the system.
Fire alarm systems generally fall into one of two categories; addressable and conventional. Addressable systems, also known as intelligent systems, enable each and every initiating device (smokes, heats, pulls, etc.), to have an individual address, or zone identifier. This is most beneficial for servicing the system. If a detector is faulty, the technician knows exactly which device is at fault. Other benefits include less cabling for the installer. The addressable devices all connect to a single loop that runs through the premises. Different types of devices can hang on the same loop.
Conventional systems are set with a certain number of zones that are hardwired to the control panel or zone expander. Smoke detectors must be run on a separate zone from pull stations, etc. There may be a dozen detectors on a single zone and if one is faulty, the technician is tasked with finding which one. More cable is required because instead of having multiple device types wired to the same loop, a separate cable run for each type of device is required for these conventional systems.
It stands to reason that addressable systems have a higher equipment cost but save on labor. A small facility, or one with a limited number of devices, may do very well with a conventional system. One is not better at detecting a fire than the other, they just utilize different technologies. There are hybrid systems as well, that mix conventional hardwired zones with addressable loops on the same control panel. They fit certain applications better than just one technology would.