To provide an alarm which dispenses with running energy such as electricity, a battery, and moreover is maintenance-free, has a permanent effect, is inexpensive, does not require an installation place, is easily moved and can extensively report in fire alarm.

This fire alarm method uses explosion sound of gunpowder and is constituted by performing moisture-proof processing or moisture-proof packaging of a 20-40 barrage of firecracker, hanging a blasting fuse having inflammability and enclosing the firecracker in a container of wire net, etc. resistant to explosion impact.