There are usually around 15 to 20 general alarms per year . The most common cause of general alarms is fire . Especially in situations that involve industries , landfills , and other facilities consisting of dangerous substances which can create hazardous smoke . The 2018 peak in alarms ( 54 that year ) is attributed to the 2018 Sweden wildfires which alone caused over 20 general alarms . Other possible attributing factors could be the increased public safety awareness after the 2017 Stockholm truck attack
2017 Stockholm truck attack
2017 Stockholm truck attack
Civil defense siren