A misfire results when explosives fail to detonate as planned during a mine blast. Accidental detonation of misfires is a frequent cause of personal injury, equipment damage, and lost production. In an effort to minimize these problems, the Bureau of Mines investigated the causes of misfires, methods for detecting misfires, and procedures for their disposal. The greatest number of misfire accidents are caused by drilling into bootlegs in underground metal and nonmetal mines. Improper disposing of misfires is the second most frequent accident category, and some accidents are due to impact initiation of explosives in the muck. Misfires are usually caused by misunderstanding, improper use, or some failure of the initiation system. Other causes are cutoffs, insufficient firing current, inadequate priming, improper explosive storage, and damage to the initiation system. Visual inspection is still the only available method for detecting misfires. Disposal of misfires in underground mines is generally by refiring; at surface mines, they are usually dug out during the mucking operation. Extreme care must be exercised when digging out misfires.
Soc. Explos. Eng., V. 9, 1983, PP. 123-132