FEATURE
Multisensors: the future of fire detection technology?
Paul Pope, head of systems integration & technical support at Apollo Fire Detectors offers advice on choosing the right multisensor detector for an application
B
y definition multisensor detectors contain more than one sensor – for
example, heat and optical. They therefore have the ability to measure multiple fire phenomena and/or different aspects of the same fire phenomenon. When combined, these readings can help discriminate between a genuine fire and a nuisance signal and then make the appropriate failsafe decision. Compared to a single sensor detector, the
decision about which multisensor detector to choose is more complicated; and that is before all the different modes and settings available are taken into account. The choices and decisions concerning
which detector types to use are initially made during fire system design but are also sometimes re-visited and even modified during commissioning and/or maintenance. They are not always well recorded nor is the rationale behind them. Multisensor detectors could be a universal solution for the protection of all life safety and property protection risks providing the appropriate compliant sensitivity modes are selected/managed to meet and maintain the fire/evacuation strategy. System designers and
engineers need to understand how the technology works and more importantly the appropriate fire engineering application of such devices.
emergency services who may not be available to respond to a genuine alarm at the same time. The fire protection industry has made
great progress in developing detectors that can recognise if a signal warrants an alarm or not. Multisensor detectors are part of the solution. Multisensor detectors are efficient in detecting real fires and ignoring false alarms if the modes are set correctly. Reputable detector manufacturers work with system designers and installers to ensure they are aware of the settings and how to configure them correctly.
Compared to a
single sensor detector, the decision about which multisensor detector to choose is more complicated...
According to the National Office of Statistics, over 300,000 false alarms were raised in the UK in 2014/15. Overall, the number of false alarms is slowly declining year-on-year, with the exception of Scotland, which has seen a slight increase for the first time in years. The FIA quotes the estimated cost of false alarms in the UK as being in excess of £1 billion a year. In addition to the cost, false alarms also take up the time and resources of the
| INDUSTRIAL COMPLIANCE
The decision on when to go to alarm is increasingly not just made by the hardware in the detector alone. Specially developed algorithms and communication protocols interconnect detectors and allow information and verification exchanges. The suitability of a detector cannot be based purely on sensor technology alone anymore. Algorithms embedded within detectors or control panels are used to change the sensitivity to fires. Each detector comes with a choice of modes and settings suited to different environments. In addition to different levels of sensitivity, these settings can include a ‘minimum
time to alarm’, ‘day/night’ sensitivity switching and
single point alarm confirmation.
Algorithms are used to improve the performance of multisensor detectors. They can also be used to combine the responses from a number of detectors to make an ‘intelligent’ system decision. Algorithms can be highly tailored and are usually designed to improve the performance of a detector in a specific environment. Well-designed multisensor detectors in carefully selected modes can detect more fires than many single-sensor detectors.
Algorithms will increase the accuracy of the detector and help to filter out most false alarms if correctly applied. Algorithms that are just designed to filter out false alarms can have dangerous consequences if they override the original sensor reading. This can be avoided by applying the and/or logic in algorithms to allow the most likely fire phenomenon (most often smoke) to set off the alarm.
The range of modes, settings and
algorithms is developed and programmed by the detector manufacturer. It is the responsibility of the system designer and Installer to apply the correct setting for the environment in which the detector is installed. This means they need to be aware of the different algorithm settings and modes. Manufacturers have a duty to make information about specific modes and settings available to ensure the safest and most suitable setting is applied always in every environment.
Apollo Fire Detectors
www.apollo-fire.co.uk T: 023 9249 2412
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