Bulgaria will sound its national siren system at 11:00 on 1 October, the interior ministry says. The drill tests the equipment and helps people learn to recognise the signals.
Sirens will sound the national alarm signal and the all-clear signal, along with a voice message.
The check happens twice a year, on the first working day of April and October. It follows rules that set out how Bulgaria's early-warning system works and how officials and the public are alerted to disasters and air raid danger.
The interior ministry says the drill also tests how the system switches on and how it broadcasts live information.