Squib (explosive)

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For other uses, see Squib.

A squib is a small explosive device which has a wide range of uses, such as generating mechanical forces as well as in pyrotechnic use. A squib can range in size from 2 to 15 millimetres in diameter. The squib, being an explosive device, releases a lot of energy, and can be used for shattering, triggering, propelling and cutting a wide range of materials.

It is different from a detonator, which is used specifically to trigger a larger explosive. A squib may indeed be energetic enough to initiate high explosives, but that is not its primary purpose. A squib is also not an electric match, which produces only a flash of flame and is used to ignite pyrotechnics and fireworks.

Squibs may be sensitive to electromagnetic radiation and devices such as vehicle radios, radar, cellular and microwave transmitters can set off a squib unless the two leads are terminated correctly or are fitted with suppressing ferrite filters.^{[citation needed]} Cellular phones have never been implicated in the initiation of explosives by direct radiation from the aerial to an igniter. Despite this, there are several urban legends surrounding the sensitivity of squibs.^{[citation needed]}

Squibs were originally made from parchment tubes, or the shaft of a feather filled with fine black powder and sealed at the ends with wax. These were inserted into the touch holes of a cannon and used to ignite the main propellant charge. Roger Bacon first described the making of squibs in 1248.^{[citation needed]} Because these early squibs needed to be kept dry ^{[citation needed]}, a "damp squib" is literally one that fails to go off due to wetting. The term has since come into general use to mean anything that fails to meet expectations.

[edit] Uses

Squibs are widely used in the motion picture special effects industry to simulate a bullet hit from a gun firing blanks. The squib is coupled with a condom or balloon of fake blood (and sometimes chunks of sponge to thicken it) for hits on persons. For hits on ricochets off other objects, items such as dust and small rocks or wood splinters are attached to the squib.

In aviation, squibs are used to generate pressurised gas to open valves and operate small mechanical devices such as those found on ejection seats, and to pierce metal diaphragms that are retaining pressurised liquids such as halon and fluorocarbon extinguishants, or release compressed nitrogen gas to act as a propellant.