Siren Day: Danish Public Warning System
The national warning system includes 1,078 sirens placed across the country.
Denmark has a national siren warning system designed to alert the population in the event of a high-risk emergency. The system includes 1,078 sirens placed across the country, covering approximately 80% of the population - so there's likely one near you.
The sirens can be activated nationwide or in specific areas depending on the situation.
If you're outside the siren coverage area, don't worry - you'll still receive alerts via S!RENEN, a mobile warning system that sends emergency notifications directly to your smartphone.
Annual Test of the Warning Sirens
Each night, the warning system is tested silently. However, once a year we have Sirenedag (“Siren Day”), when the sirens are tested with sound. This takes place on the first Wednesday of May.
So please don’t be alarmed if you hear a loud, unsettling noise or your phone behaves strangely. The test begins at 12:00 noon and lasts for 10 minutes. It includes both the “Danger” signal and the “All Clear” signal.
The purpose of this test is not only to ensure the sirens are functioning properly, but also to remind everyone what the signals sound like and how to respond in an actual emergency.
What Is S!RENEN?
S!RENEN is a public warning system that sends alerts directly to your mobile phone if you are in a danger zone. It includes a loud alarm sound and a text message with relevant information and instructions. Messages are provided in both Danish and English.
You do not need to download an app or register – the alerts are transmitted via mobile masts. The system works on most smartphones and does not require a Danish SIM card
Understanding the Signals
Here’s a quick guide to help you recognize the siren signals:
12:00 – “Danger” signal: A distinctive sound that rises quickly and then falls slowly. It repeats four times over 45 seconds, with short pauses in between.
12:04 – Repetition of the “Danger” signal.
12:08 – “All Clear” signal: A single, long monotone lasting 45 seconds. This indicates that the danger has passed, and it is safe to go outside.
In Case of a Real Emergency
Although high-risk emergencies are rare in Denmark, it's important to know how to respond:
Go indoors immediately if you hear the Danger signal
Check your phone for a S!RENEN alert
Tune in to Danish news channels such as DR or TV2 for updates or seek for information via your phone
Stay inside until you hear the All-Clear signal appears
Visit this page to find easy-to-understand guides in other languages.