Alarm monitoring arrangement

In an alarm monitoring arrangement, notification of an alert condition from a detector is deferred for a period of time determined in dependence on any history of false alerts from the detector. Thus in an environment having multiple detectors, any detector giving transmitting an alert and then clearing the alert prior to expiry of the allocated time period has its "time to respond" period increased in respect of subsequent activation. Periodically the time periods in respect of each detector may be reduced so that normally non-alerting detectors attain a shorter respond period than poorly positioned detectors which create most false alerts. The time period prior to response may be bounded by pre-determined maximum and minimum response periods.