An emergency population warning or public warning system is a method whereby local, regional, or national authorities can contact or notify members of the public to warn them of an impending emergency. These warnings may be necessary for a number of reasons, including:
weather emergencies such as cyclones, flooding, tornadoes, avalanches and severe weather; geological disasters such as earthquakes, landslides, volcanic eruptions, and tsunamis; industrial disasters such as the release of toxic gas or contamination of river water; radiological disasters such as a nuclear plant disaster; medical emergencies such as an outbreak of a fast-moving infectious disease or pandemic; warfare such as air raids or acts of terrorism; and other events, such as prison escapes, abducted children or emergency telephone number outages.
Warnings are often disseminated during urgent events such as evacuations or where a severe threat to life is expected. Common alerting methods include sirens, radio, television, local media, telephone, SMS and Cell Broadcast.
Requirements
In order to develop an effective emergency warning system, certain agreements or procedures are established, including:
an agreement as to what constitutes an emergency in the area served by the system. This differs from region to region depending on the local climate, geology, and other factors. an agreement as to who can initiate an alert. In some countries all warnings are transmitted by a single command centre, while in other larger countries a host of local, regional, and national agencies can be authorized to initiate warnings. at least one system by which the information can be quickly transmitted to the population. This includes the method and technology used. an education program to teach the general public how to recognize an alert or what to do if a warning is broadcast.
America region
Canada
On 11 June 2009, the Canadian Radio-television and Telecommunications Commission (CRTC) approved a proposal by Pelmorex, owners of The Weather Network and MétéoMédia, to receive must-carry status for the channels, in exchange for developing a "national aggregator and distributor" of localized emergency alert messages compliant with the Common Alerting Protocol. The alert system, known as Alert Ready, built on a backend known as the National Alert Aggregation and Dissemination system (NAAD), was first established in 2010, and further expanded as a result of consultation with government officials, broadcasters, and the CRTC. In August 2014, the CRTC ruled that all television stations, radio stations, and broadcast distribution undertakings had to begin mandatory carriage of local alerts relayed through NAAD by 31 March 2015.
The province of Alberta had its own system called the Emergency Public Warning System (EPWS). The EPWS was put into place after a major tornado swept through the city of Edmonton in 1987, killing 27 and causing millions of dollars in damage. Unlike the American EAS, however, broadcast of the EPWS was not mandatory on radio and television stations. It was broadcast on the CKUA Radio Network and was televised on CTV Two Alberta and other participating stations. EPWS warnings could be initiated by municipal police and fire departments, the provincial government, county authorities, tribal government agencies, Environment Canada, and the Royal Canadian Mounted Police. CKUA developed and maintained the EPWS until January 2010, when it lost a bid to modernize the system to an outside vendor (the contract had provided 15% of the station's overall budget).
In June 2011, an updated version of the system known as Alberta Emergency Alert was introduced, which emphasized multi-platform availability of alerts and advisories on digital platforms, such as online and through a mobile app. Participation in AEA is now considered mandatory under the CRTC's national public alerting mandate.
Chile
The SAE (Spanish: Sistema de Alerta de Emergencia; English: Emergency Alert System) was created as a response to the 2010 Chilean Earthquake after the failure by the national authorities to provide safety precautions and speedy information during the aftermath of the disaster. Since its inception in 2012 and through its official implementation in 2017 onwards, it has been used to provide alerts and information regarding natural disasters such as floods, wildfires, tsunami and earthquake warnings. All cell phones on sale in the country are required by law to be compatible with the SAE system since 2017.
South America
Many countries in South America have a mechanism called "cadena nacional" (). It enables the leader of the country to address the people simultaneously on all TV channels and radio stations, interrupting normal programming. In some countries, such as Argentina and Venezuela, the broadcast of these messages is obligatory. Many of these systems were created by past military governments, and political use of the mechanism is common.
United States
The bulk of emergency warnings in the United States are sent through the Emergency Alert System, implemented in 1997. The EAS can be activated by national, state, regional, or local authorities, including police, fire, weather, and other governmental authorities. EAS is often activated when an unexpected emergency such as a tornado, earthquake, or release of toxic gas happens. The vast majority of EAS alerts are generated by the National Weather Service. There is also a National Volcano Early Warning and Monitoring System.
The Integrated Public Alert and Warning System (IPAWS) program of the US Federal Emergency Management Agency is an attempt to integrate multiple public warning technologies into a coordinated nationwide "system of systems" using the Common Alerting Protocol. Systems targeted for inclusion in IPAWS include the Emergency Alert System, the Commercial Mobile Alert System using cellular telephones and other wireless devices and the NOAA Weather Radio network.
Many states use existing air raid sirens to warn of tornadoes and flash floods. People living near certain nuclear facilities such as the Hanford Site in Washington have special radios in their home that are set to broadcast a warning signal in the event of a radiological emergency. Some emergencies, such as Amber alerts, are also sent out via e-mail, cellphone text message, and highway signs. Many U.S. institutions of higher education now use multiple warning technologies on their campuses, including outdoor and indoor sirens, public address systems, email and cell phone text messaging, and digital displays.
Prior to the adoption of the Emergency Alert System, the United States used CONELRAD from 1951 to 1963 and the Emergency Broadcast System from 1963 to 1997. Cable television systems in the United States also have emergency warnings at the time, known as Local Access Alert or Emergency Override System.
A notable example of an emergency alert being issued in the United States was a nationwide alert test, known as the National Periodic Test, which last occurred on 4 October 2023.
Africa region
The United Nations' "Early Warning for All initiative" was seeking geo-located cell broadcasting and location-based SMSs by 2027. Several countries have cell broadcast systems.
Kenya
Kenya's Trilogy Emergency Relief Application (TERA) system commenced in 2015.
Mauritius
Mauritius developed a location-based system in 2023.
South Africa
South Africa operates a cell broadcast system. The country faces challenges of floods, bushfires, and earthquakes, separate to disaster data management by government agencies. It was first proposed in 2014, following Kenya's implementation.
Tanzania
In February 2025, Tanzania started developing their emergency communication infrastructure to include cell broadcast technology.
Tunisia
Tunisia developed an SMS-based system in 2023.
Asia region
Iran
Iranian armed forces texts are sent on several occasions. Also texts are sent by US just as well.
Japan
Since 2013 the Emergency Warning System alerts people to the significant likelihood of catastrophes.
The J-Alert system launched in 2007 aims to allow government officials to address the population directly via loudspeakers. It aims to cover earthquake, tsunami, volcano, and military emergencies.
The Earthquake Early Warning system is operated by the Japan Meteorological Agency. It is capable of delivering warnings a few seconds before S-waves can propagate to distant locations. Warnings are broadcast by radio and television stations, and compatible equipment can automatically turn on when receiving a message. EEW capability is also required for all domestic cell phones sold after 2007.
JMA also issues advisories regarding tropical cyclones in the western Pacific Ocean.
Philippines
The emergency broadcast system for mobile devices was introduced in 2017.
Europe region
Generally
Many countries utilise the EU-Alert standard for mobile devices.
France
In France, the population warning is made via air raid siren. This network is called the "Réseau national d'alerte" (RNA). The system is inherited from the air-raid siren network (défense passive) developed before World War II. It consists of about 4,500 electronic or electromechanical sirens placed all over France.
In some cases, the warning signal may be played by a mobile system installed on the fire department's vehicles.
The warning signal is described by décret (by law) of 23 March 2007. It consists in a modulated sound going up and down (up to 380 Hz) during the first minute, and repeated three times. The end of alert is a continuous signal lasting 30 seconds.
The system is tested the first Wednesday of every month at 11.45 in the north, 12.00 in the centre, and at 12.15 in the south; for tests, the modulated signal is played only once.
When the warning signal sounds, people are expected to remain at home or the building they are in and listen to further instructions on radio via France Info, France Inter, or local stations.
Instructions may also be announced by police or fire department vehicles.
FR-Alert
FR-Alert is a national-level mobile risk alert and emergency communication system implemented by Intersec in partnership with the Ministry of the Interior in France. This system is designed to facilitate the efficient dissemination of critical alerts and safety information to citizens throughout the country. FR-Alert serves as a platform for delivering timely and accurate notifications related to various potential risks, including natural disasters and industrial incidents.
Norway
The emergency broadcast system for mobile devices was introduced in 2023, and based on EU-Alert.
Sweden
The VMA (Swedish: Viktigt meddelande till allmänheten; English: Important public announcement) is the emergency warning system used to alert the public in case of accidents, serious events, or disruptions of important services. These warnings are broadcast through different channels: via radio and television. from krisinformation.se on either the website, app, or social media. as notifications in the Sveriges Radio app, SR Play. as text messages to your mobile phone. via outdoor warning signals.
These sources of information are however primarily broadcasting in Swedish, information in English may initially be limited. Non-Swedish speakers are directed to use translation tools to keep up with warnings and directions from the authorities.
In addition to these already existing avenues to broadcast Important public announcements the warning system SE-Alert is currently planned to start implementation by the summer of 2026. This system is going to use cell broadcast technology to simultaneously broadcast to all cellphones in the affected area of the cellular network.
United Kingdom