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Basic Information

A small, sealed package of primary high explosive which is fired to set off a much larger charge of secondary explosive. Triacetone triperoxide, hexamine citrate, various picrates and some azides are compounds commonly used as fillers for detonators, as are a variety of other compounds.
The filler is normally triggered by a burning fuse or by an electrical current (either working directly on the filler or, more normally, heating a metal resistance wire embedded in the filler), although friction and impact primers and mechanisms that use a reactive chemical (e.g. an acid) for triggering are also known.

The detonator is attached to a fuse, an electrical circuit or a length of detonator cord (if appropriate) and inserted into the mass of the secondary. Once initiated the system works through any built in delay and the fires - the fuse (or whatever) triggers the filler of the detonator, which explodes, triggering the secondary and delivering the blast. On occasion the secondary may be used to trigger a still larger explosion, acting as some kind of detonator in its own right, e.g. the firing of a large quantity of ammonium nitrate fertiliser with a small quantity of plastic explosive which is triggered in its turn by a detonator - at one time a popular party trick of the PIRA and their fellow travellers.

For reference, the quantity of explosive inside a detonator is usually 'only' enough to mangle the hand of someone who handles it without sufficient respect - they're not terribly useful as weapons in their own right - you'd probably need to fire one inside someone to kill them…

Also known as "det caps" and "crackers" amongst those who work with them a lot.


1. full source reference

Game and Story Use

  • These are the component of an explosive charge where failures tend to be most common - either misfires on firing or explosions during manufacture. When a character botches a relevant skill roll, chances are there's something up at the detonator.
    • A bad or inert batch of caps is a common problem - intelligence agencies (and to a lesser exent police) may occasionally release weak or inert caps into the black market to foil would be bombers. By their nature caps cannot be tested without being used.
    • Sabotaging caps so that they explode on installation has also been used historically as a way of killing enemy bomb-makers. HM Special Forces were "alleged" to have used this tactic on PIRA arms dumps located by intelligence operations and thus accounted for several of the PIRAs more valuable powder monkeys.
  • Pulling the detonator out of the secondary can be remarkably effective.
  • Detonator cap parts can be surprisingly resilient and can provide investigators with important evidence about their origins even after firing (serial numbers from the end of the cap seem to survive quite a lot).
  • A cap can also be used as a small explosive charge in its own right - although it's not good for much.
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