Squib (explosive)

A squib is a miniature explosive device used in a wide range of industries, from special effects to military applications. It resembles a tiny stick of dynamite, both in appearance and construction, although with considerably less explosive power. Squibs consist of two electrical leads which are separated by a plug of insulating material, a small bridge wire or electrical resistance heater, and a bead of heat-sensitive chemical composition in which the bridge wire is embedded. Squibs can be used for generating mechanical force, or to provide pyrotechnic effects for both film and live theatrics. Squibs can be used for shattering or propelling a variety of materials.

A squib generally consists of a small tube filled with an explosive substance, with a detonator running through the length of its core, similar to a stick of dynamite. Also similar to dynamite, the detonator can be a slow-burning fuse, or as is more common today, a wire connected to a remote electronic . Squibs range in size, anywhere from .08" up to 6/10" (~2 to 15 millimeters) in diameter.

In the North American film industry, the term squib is often used to refer variously to: electric matches and detonators (used as initiators to trigger larger pyrotechnics). Squibs are generally (but not always) the main explosive element in an effect, and as such are regularly used as “bullet hits”. Conventional squibs fire once, with the exception of eSquibs, which fire 200 or more times before depletion.

Squibs were once used in coal mining to break coal away from rock. In the 1870s, some versions of the device were patented and mass-produced as "Miners' Safety Squibs".

...
Wikipedia