False Alarms

One of the biggest problems with alarm systems is that of the false alarm. In the metropolitan police area no less than 98 percent of the call-outs are for false alarms. Understandably the police see this as a considerable waste of their time and resources. Some forces have laid down conditions as to how far they will respond: for example, more than five false alarms in any month and the owner is warned; after three months of nuisance calls there is no further police response to an alarm because it is considered a false alarm.

Apart from police involvement, the goodwill of neighbors will inevitably be jeopardized and strained by frequent false alarms, to say nothing of the trauma experienced by the householder who is frequently disturbed from his bed, or called home by the police during the day. It is the high incidence of false alarms that has resulted in general skepticism and the common ignoring of alarms when they sound.

A trick that has been used by some burglars is to try to deliberately set off the alarm in some way without making an obvious entry. The householder, thinking it is another false alarm, and not wishing to be disturbed again, switches the alarm system off. The National Supervisory Council for Intruder Alarms (NSCIA) code of practice actually recommends not switching the system on again after a false alarm. So when the fuss has died down the intruder breaks in, secure in the knowledge that he will not be disturbed.

This ruse can only work if the system is prone to false alarms and can be triggered from the outside or without causing obvious damage. Illustrating how over-sensitive some systems are is the fact that one night in October 1987 a security firm in the London area logged 3000 calls in a period it would normally receive only a dozen calls. The police computer handling incoming calls broke down under the strain. All these false alarms were caused by hurricane winds. The false alarms were due entirely to the high winds and their effects.

It can be seen, then, that the false alarm must be avoided above all else, but in a way that does not compromise security. It can be done, as there are a large number of effective installations that rarely if ever experience one. Human error is sometimes to blame, and little can be done about that except to stress extreme care by everyone concerned. Most of the trouble lies in the installation of the system or the use of unsuitable sensors.