Understanding warning signals and sirens and responding correctly

Modern warning systems use several channels at the same time. Sirens are loud and reach people who are asleep or not looking at their phones, but carry no content. Warning apps deliver detailed texts with location, hazard and instructions, but have to be installed. Cell broadcast sends a warning to all phones currently connected to the mobile network in a particular area, without needing an app. Radio and television interrupt their programmes for announcements, and sometimes vehicles with loudspeakers drive through the streets.

The basic idea is a two-step process: an alert gets your attention, and then you look for the information. Only the information tells you whether to stay inside, leave the area or do nothing at all. So a siren alone does not automatically mean danger for you, but it always means: check now.

Every channel has weaknesses. During a power cut, the mobile network can be overloaded or fail; sirens do not exist everywhere; and some people hear poorly or do not use a smartphone. That is why it is wise to have at least two channels – for example a phone plus a battery radio.

Siren signals are not the same everywhere. In Germany, for example, the BBK describes a one-minute rising and falling tone as a warning and a one-minute continuous tone as the all-clear. Other countries use different tones, durations or meanings, and signals can change. So look up with your municipality or civil protection what applies where you live.

If you have just moved or are travelling, it is worth sorting this out right at the start. At your holiday destination, ask your accommodation how warnings are given – sirens, apps, loudspeakers or hotel staff – and where to go in case of a tsunami, storm-surge or wildfire warning.

This entry deliberately contains no complete list of national signals. Local information is always the most reliable.

When you hear a warning, go into a building, bring children and pets inside and close windows and doors. Then switch on the radio or warning app and follow the instructions. For some hazards, such as a fire with smoke or a chemical accident, the authorities will also say to switch off ventilation. For others, such as a flood, the instruction may be to leave the area.

A common mistake is ignoring a siren because you 'can't see anything' outside. Many hazards are invisible or far away – toxic gases, smoke that arrives later or a flood wave upstream, for example. It is just as wrong to call the emergency number to ask about the reason. The emergency number is for people in acute need – you get information from the radio, warning apps and official websites.

When the danger has passed, an all-clear is given. Until then, stick to what the authorities have said.

Preparation takes only a few minutes: keep cell broadcast enabled on your phone, install your country's official warning app, keep a battery radio with spare batteries and note the frequency of the regional broadcaster. A crank or solar radio is a good addition but not a must.

People who cannot hear sirens or cannot use apps need a second channel – neighbours, relatives or special warning services, for example for deaf people. When you receive a warning, inform older neighbours and people without a smartphone. Pass on only official content, no rumours and no unverified messages from social media.

Businesses, schools and clubs also benefit from clear procedures: who follows the warnings, who informs whom, and where is the assembly point?

Many countries run regular test alerts, in Germany for example a nationwide warning day. This is a good opportunity to check whether the warning really reaches you: can you hear the siren in your home? Does your phone ring? Does the app show an alert?

Also use the day to briefly discuss in the household what you will do in a real warning: who closes the windows, where is the radio, who calls grandma? Children understand sirens better if someone has explained beforehand that the sound means 'attention, check' and is no reason to panic.