Science Bar

Thursday 10 December 2015

Fire Alarms

A fire alarm system is number of devices working together to detect and warn people through visual and audio appliances when smoke, fire, carbon monoxide or other emergencies are present. These alarms may be activated from smoke detectors, and heat detectors. Alarms can be either motorised bells or wall mountable sounders or horns.

Primary power supply: Commonly the non-switched 120 or 240 volt alternating current source supplied from a commercial power utility. In non-residential applications, a branch circuit is dedicated to the fire alarm system and its constituents. "Dedicated branch circuits" should not be confused with "Individual branch circuits" which supply energy to a single appliance.

Secondary (backup) power supplies: This component, commonly consisting of sealed lead-acid storage batteries or other emergency sources including generators, is used to supply energy in the event of a primary power failure.

Initiating devices: This component acts as an input to the fire alarm control unit and are either manually or automatically activated. Examples would be devices pull stations, heat detectors, or smoke detectors. Heat and smoke detectors have different categories of both kinds. Some categories are beam, photoelectrical, aspiration, and duct.

After the fire protection goals are established – usually by referencing the minimum levels of protection mandated by the appropriate model building code, insurance agencies, and other authorities – the fire alarm designer undertakes to detail specific components, arrangements, and interfaces necessary to accomplish these goals. Equipment specifically manufactured for these purposes is selected and standardized installation methods are anticipated during the design.

Some fire alarm systems utilize emergency voice alarm communication systems (EVACS) [6] to provide pre-recorded and manual voice messages. Voice Alarm systems are typically used in high-rise buildings, arenas and other large "defend-in-place" occupancies such as Hospitals and Detention facilities where total evacuation is difficult to achieve.

TTUTORIAL LINK: http://m.youtube.com/watch?v=IaGQMxPap5o


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