Disruptions caused by false alarms may result in public panic, which often initiates actual disasters. Moreover, the suspension of services and the evacuation of public environments because of false alerts unnecessarily paralyse commerce and personal endeavours.
A 1992 study shows the number of suspect package alerts in the London Underground quadrupled to 2,004 from 1990 to 1991. The majority of disruptions to the functioning of the Underground in 1991 were caused by 3,750 false alarms. Of the 1,000 evacuations that year, only 274 were caused by actual fires, all of which lasted no more than 3 minutes. The study estimates the cost of disruption at £15 million a year in lost working time (£10 million from fire reports and £5 million from suspect packages).
The cost of reacting to false alarms is worth the potential reality of danger.