The Pipe bomb reference article from the English Wikipedia on 24-Apr-2004
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Pipe bomb

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A pipe bomb is any homemade explosive device encased in a piece of ordinary plumbing pipe. The pipe makes a convenient container for the bomb, and creates shrapnel when it explodes.

Although the risk of premature detonation cannot be stated in terms of frequency, it is a possible outcome of attempting to construct any homemade explosive device. Documented instances of unintentional detonation during assembly are common, often resulting in serious injury or death to the manufacturer.