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FIRE DETECTION AND ALARMS

The choice of fire alarm system depends on the building structure, the purpose and use of the building and current legislation. In new or altered buildings the enforcement body is the local building control, and the relevant guidance is explained in section new or altered buildings. All existing buildings except domestic premises are subject to The Regulatory Reform (Fire Safety) Order 2005 and the Responsible Person, as defined in the order, has to conduct a fire risk assessment. This FRA will decided the appropriate British standard necessary to provide a suitable and sufficient solution for the premises. The enforcement body is the Fire and Rescue Service and the Department of Communities and Local Government (DCLC) have published a number of guidance documents for premises subject to the RR(FS)O. This is particularly important since none of the legislation gives any detailed information on the type of system required but the guidance usually indicates appropriate British standards. The main standard for fire alarm systems is BS5839 pt1:2017.

This guidance contains brief descriptions of the major components which go to make up a fire alarm system. The points to be considered are intended to highlight the variables which can exist and need to be considered whilst designing and compiling a specification for component parts.

It is not the object of this note to consider the details of different circuit types or to discuss their relative merits.

Types of Fire Alarm Systems

Conventional Fire Alarm System

In a Conventional Fire Alarm System, a number of call points and detectors are wired to the Fire Alarm Control Panel in Zones. A Zone is a circuit and typically one would wire a circuit per floor or fire compartment. The Fire Alarm Control Panel has a number of Zone Lamps. The reason for having Zones is to give a rough idea as to where a fire has occurred. This is important for the fire brigade and of course for the building management. The accuracy of knowing where a fire has started is controlled by the number of Zones a Control Panel has and the number of circuits that have been wired within the building. The Control Panel is wired to a minimum of two sounder circuits which could contain bells, electronic sounders or other audible devices. Each circuit has an end of line device which is used for monitoring purposes.

Addressable Systems

The detection principle of an Addressable System is similar to a Conventional System except that the Control Panel can determine exactly which detector or call point has initiated the alarm. The detection circuit is wired as a loop and up to 99 devices may be connected to each loop. The detectors are essentially Conventional Detectors, with an address built in. The address in each detector is set by dil switches and the Control Panel is programmed to display the information required when that particular detector is operated. Additional Field Devices are available which may be wired to the loop for detection only i.e. it is possible to detect a normally open contact closing such as sprinkler flow switch, or a normally closed contact opening. Sounders are wired in a minimum of two sounder circuits exactly as a Conventional System. Loop Isolation Modules are available for fitting on to the detection loop/loops such that the loop is sectioned in order to ensure that a short circuit, or one fault will only cause the loss of a minimal part of the system.

Aspirating Smoke Detection Systems

Aspirating technology works by detecting microscopic evidence of fire at the pre-combustion stage, long before visible evidence of smoke or flame is evident. The average speed of detection rate will be in excess of 30 times that of a conventional smoke detector.

In contrast to inactive smoke sensing devices which includes spot sensors, Aspirating Smoke Detection systems intentionally attract smoke particles towards the sensor by means of drill out holes inside of a piping strategy that operates through the entire protected region.

In addition, Air Sampling Smoke Detection systems encompass reliability supervising to make sure a fault signal is given at any moment the Air Sampling Smoke Detection’s capability to sense smoke particles is affected. This isn’t the situation with inactive systems which are usually simply electrically supervised without having the capability to decide if the smoke can really get through to the detection component.

Aspirating Smoke Detection systems consist of one or more degree of alarm, usually configurable. This enables an Air Sampling Smoke Detection system to deliver extremely early notification of a situation, forcing inspection within the earliest smoldering phase of a fire enabling the fire to be effortlessly dealt with. Additional alarm stages can be set up to deliver fire alarm inputs to fire systems including activation fire Extinguishing systems. Air Sampling Smoke Detection alarm sensitivities are adjustable and can be designed to adjust to various levels starting from many, many times more susceptible than the usual traditional detector, to a reduced amount of sensitive. The detectors perform best within non-volatile conditions. They may also be applied in computer system cabinets to inform end users towards the getting hot of computer cabling or certain computer components.

Voice Evacuation Alarm Systems

A voice alarm system (sometimes referred to as a voice evacuation system) is installed with the safety of staff and general public in mind. It is a system that assists in the effective evacuation of an area or building during a fire, bomb alert or other emergency. At all other times a voice alarm system is used to make public address announcements, broadcast advertisements or background music. All broadcasts, be they live announcements or continual music, can be sent to all areas of a site or to selected areas (referred to as zones).

Research has proven that in an emergency people will react without confusion or panic if they receive a clear, intelligible message. These messages are stored within a voice alarm system. Traditional bells and sounders only give a warning, they do not indicate the nature of the emergency, leaving people uncertain and often such signals are ignored – with fatal consequences. A voice alarm system provides clear easily understood instruction via pre-recorded messages. This method ensures that even untrained personnel and the general public are evacuated speedily and efficiently.

A voice alarm system has to work when needed – during an emergency – and is, therefore, fully monitored at all times. It is also backed up by batteries which are fully charged and checked constantly; this will ensure that, even during a mains power failure, the system will continue to operate. A combination of clear pre-recorded messages and live announcements (to selected areas) enable a controlled and gradual or ‘PHASED EVACUATION‘. Phased evacuation methods enable selected areas to be evacuated in turn – typically those in most danger are evacuated first whilst surrounding areas (zones) are put on ‘alert’. The voice alarm system works automatically, with all controls easily overridden by fire officers or building control when needed..

Wireless Fire Alarm Systems

Wireless fire alarm systems are an excellent option for many usage cases. They are easy to install and the lack of significant wiring makes them ideal for situations where rewiring a building isn't an option. The sounder and call point units can be battery-powered, allowing them to be used in locations where a viable power point is not available.

Wireless fire alarms broadcast their signals on encrypted channels, which are reliable and closed to any interference. The range of the units varies according to needs and we offer repeater units and extension aerials that extend the signal range, allowing you to cover any size of property. Many of the call points and audio visual units we sell are waterproof, which, combined with the lack of need for wiring, makes wireless alarm systems ideal for outside usage needs.