Intelligent response
All fires have three elements in common, in that they produce CO, heat and smoke. The proportions however will be different in each case, as will the time when each element is released. Similarly, a fire will almost certainly produce a changing light signature, primarily as a result of flame development.
Just as a human being picks up on these changes through the use of different senses, the latest sophisticated multi-criteria devices, typified by Honeywell's Smart⁴ detector, combine the four sensing elements of CO, IR, smoke and heat detection within a single unit in order to detect different kinds of fire faster.
Further, with sensors managed by advanced algorithms these can be configured to operate normally at a high immunity level, instantly changing to become very sensitive to fires as soon as fire characteristics are sensed. Critically therefore, transient nuisances are ignored, so minimising the false alarm rate.

Looking ahead
So, is multi-criteria detection the way ahead for fire protection? This would certainly appear to be the case, as CO devices, for example, become more commonplace and combined optical/thermal devices have moved from their earlier niche positioning to more mainstream application.
More broadly, the fire industry generally across Europe is moving - subtly perhaps yet demonstrably - from the stance of 'let's detect fire better' to one which might be characterised as 'let's prevent false alarms'.
The reason for this, not surprisingly, is primarily economic, as the cost of downtime or lost business increases, together with a loss of confidence in the system itself. As a result, the reduction in false alarms is now a principal product development focus within major fire safety equipment manufacturers.
And here, critically, multi-criteria sensors are inherently less prone to false alarms than their single sensor counterparts, as it is more difficult to falsify two criteria than one, three more than two, and so on.

At the same time, as development concentrates on providing increasing resilience against false alarms, so infrared technologies are also proving significantly more capable than optical detectors in picking up fast flaming fires in delivering equivalent performance to earlier ion detectors. So, in the case of those manufacturers developing dual frequency or dual angle optical detectors, for example, though a step forward these do not provide the true replacement provided by an infrared solution. Thus, from the perspective of both earlier fire detection and minimising false alarms, the concept of multi-criteria detection has established itself as a mainstream technology response.

Key applications
Having said that multi-criteria detectors are moving centre-stage, two caveats should be introduced at this point. First, as a relatively expensive solution, full multi-criteria protection is ideally suited to those applications where the cost of downtime to the business is especially significant.
In such situations, though the early detection capability of a multi-criteria solution is valuable, resilience against false alarms is likely to be the determining factor from a commercial perspective.
Thus, multi-criteria protection is ideally geared for use in such environments as hotels who offer refunds in the case of evacuations for false alarms, financial institutions undertaking large volumes of high value transactions or mission-critical areas within airports, for example. At the same time, it is well-suited to sports and leisure industry applications, where there are often large numbers of people in a single location.

Similarly, multi-criteria protection is an example of general application, so will not be suited to other areas where the cost of downtime is significant, such as industrial processes which use chemicals that become airborne and can be aggressive to plastics or environments where major temperature variation is commonplace, which continue to require specialist detectors.

Yet as in any newly emerging technology, as the cost of multi-criteria devices comes down and the differential with traditional fire detection solutions narrows, so their applicability will inevitability become broader.

http://www.honeywell.com/

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