When J-ALERT issues a ballistic missile warning: what to do outdoors, indoors and in a car

The short answer

If J-ALERT broadcasts a ballistic missile warning, go inside a nearby building or underground if you are outdoors, and move away from windows if you are indoors. The Cabinet Secretariat notes that a ballistic missile could arrive less than 10 minutes after launch. There is little time to think on the spot, so knowing what to do beforehand is the preparation.

This article sets out only what the Cabinet Secretariat's civil protection portal and the Fire and Disaster Management Agency (FDMA) say, as actions to know for an emergency.

What J-ALERT is

J-ALERT (the nationwide instant warning system) delivers urgent information from the national government to residents in a short time. According to the FDMA white paper, it carries civil protection information such as ballistic missile warnings, as well as Earthquake Early Warnings, tsunami warnings and emergency weather warnings.

The information reaches local governments by satellite and terrestrial lines, automatically starting municipal disaster radio systems that broadcast from outdoor loudspeakers. At the same time it reaches smartphones as an emergency alert message (Area Mail / Emergency Alert Mail) from the mobile carriers. For ballistic missile warnings, municipal radio plays the civil protection siren. On smartphones, however, the alert tone is the same one used for tsunami and volcano alerts.

According to the Cabinet Secretariat's Q&A, J-ALERT is not used when a missile is judged to have no chance of landing in, or passing over, Japan's territory or territorial waters.

What to do, by location

The building does not need to be a designated shelter. Staying away from windows protects you from glass shattered by a blast.

How messages progress, and if something lands nearby

On the civil protection portal, the first "launch information" calls on people to go inside a building or underground. If the missile may land in Japan, a follow-up message says "evacuate immediately" and gives the expected time and place of landing. Later messages ask people to keep sheltering indoors, or report that the missile has passed over or that the warning is lifted. Depending on the situation, not every stage is sent.

If something lands nearby and you are outdoors, cover your mouth and nose with a handkerchief, leave the area at once and move into a well-sealed building or upwind. If you are indoors, turn off ventilation fans, close the windows and seal the gaps. If you find a suspicious object, do not approach it; contact the police, fire service or Japan Coast Guard. Stay indoors until the all-clear, and check official information on TV, radio or the internet.

What to check in advance

The FDMA runs a nationwide J-ALERT transmission test, in principle four times a year, to make sure the system works. On test days, municipal radio broadcasts "This is a J-ALERT test" (in Japanese). Checking whether you can hear it at home and at work gives you an idea of how a real alert would sound there.

[Where we would shelter]
Home: room without windows -> (e.g.) hallway, bathroom
Work: nearby building or underground -> (e.g.) the building's basement level
On the commute: (e.g.) the station's underground passage
Driving: where we could stop safely