Short answer. Denmark warns the public through about 1,000 outdoor sirens, the S!RENEN cell broadcast system on mobile phones, and emergency announcements on DR and TV 2 1. When you hear the sirens, go indoors and look for information from DR or TV 2 2. Sirens and S!RENEN are tested once a year, on the first Wednesday of May at 12:00 3.
How does Denmark warn the public?
Through several channels at once 145:
- Outdoor sirens: about 1,000 sirens covering about 80% of the population in built-up areas 1.
- S!RENEN: a cell broadcast warning sent to phones in the danger area 4.
- DR and TV 2: emergency messages; DR radio if other systems fail 1.
- Other channels: politi.dk, authorities' websites and social media; in rare cases the police go door to door 1.
The National Police (Rigspolitiet) sends S!RENEN alerts and activates the sirens; the Danish Emergency Management Agency (Beredskabsstyrelsen) runs both systems 14.
What do the siren signals sound like?
| Signal | What you hear | Source |
|---|---|---|
| Danger | A tone that rises quickly and falls slowly, repeated four times over 45 seconds; the signal is repeated after four minutes | 2 |
| All clear | A long steady tone lasting 45 seconds, sounded eight minutes after the alarm | 2 |
What should I do when I hear the sirens?
The official instruction is: "GÅ IND OG SØGE INFORMATION HOS DR ELLER TV 2" (go indoors and look for information from DR or TV 2) 2. Keep a radio that works without mains power: the Danish checklist includes an FM radio powered by batteries, hand crank or solar cells, and a car radio may do 5. See /guides/emergency-radio and, for the reasoning behind going indoors, /guides/shelter-or-evacuate.
What is S!RENEN and do I need to install it?
S!RENEN is a cell broadcast warning system. It is not an app: there is nothing to download and no registration 4. Phones in the danger area receive the alert automatically, vibrate and show a text saying what is happening, where, and what to do 4. It requires an iPhone 8 or newer with iOS 16.4 or newer, or generally Android 11 or newer 4.
The rule on receiving a message is: STOP. LÆS. REAGÉR. (Stop. Read. React.) 4
When are the systems tested?
Sirens and S!RENEN are tested on the first Wednesday of May at 12:00 3. Sirens are also checked silently every night 3. S!RENEN test messages begin with "TEST - SIRENEN – TEST" and say that no action is needed 4.
What if I am deaf or hard of hearing?
Deaf and hard-of-hearing people can register for SMS alerts via borger.dk 1.
Frequently asked questions
Will S!RENEN work on my phone?
On an iPhone 8 or newer with iOS 16.4 or newer, or generally on Android 11 or newer. No app or registration is needed 4.
How long does the danger signal last?
The rising and falling tone is repeated four times over 45 seconds and the signal is repeated after four minutes 2.
How do I know the danger is over?
A long steady tone lasting 45 seconds, sounded eight minutes after the alarm, is the all clear 2.
Who decides to sound the sirens?
The National Police (Rigspolitiet) 1.
Sources
- Beredskabsstyrelsen — Sådan advarer myndighederne dig, når der er fare på færde — https://www.brs.dk/da/borger/var-klar-nar-krisen-rammer/sadan-advarer-myndighederne-dig-nar-der-er-fare-pa-farde/ (accessed 2026-10-20)
- Beredskabsstyrelsen — Det skal du gøre, når du hører sirenerne — https://www.brs.dk/da/borger/var-klar-nar-krisen-rammer/det-skal-du-gore-nar-du-horer-sirenerne/ (accessed 2026-10-20)
- Beredskabsstyrelsen — Den årlige test af varslingskanalerne — https://www.brs.dk/da/borger/var-klar-nar-krisen-rammer/sadan-advarer-myndighederne-dig-nar-der-er-fare-pa-farde/den-arlige-test-af-varslingskanalerne/ (accessed 2026-10-20)
- Beredskabsstyrelsen — S!RENEN — https://www.brs.dk/da/sirenen/ (accessed 2026-10-20)
- Danish Emergency Management Agency (hosted by Styrelsen for Samfundssikkerhed) — Be prepared for a crisis — https://samsik.dk/wp-content/uploads/2025/08/EN-prepared-for-crises.pdf (accessed 2026-10-20)
Turn this into action
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Sources
- Beredskabsstyrelsen · Sådan advarer myndighederne dig, når der er fare på færde checked 2026-10-20
- Beredskabsstyrelsen · Det skal du gøre, når du hører sirenerne checked 2026-10-20
- Beredskabsstyrelsen · Den årlige test af varslingskanalerne checked 2026-10-20
- Beredskabsstyrelsen · S!RENEN checked 2026-10-20
- Danish Emergency Management Agency (hosted by Styrelsen for Samfundssikkerhed) · Be prepared for a crisis checked 2026-10-20