PrintLesson 6.5: Fire in the Hole
Prior to setting off a blast, the blaster would yell, “fire in the hole – fire in the hole – fire in the hole.” This still occurs today, but not as frequently because loud sirens or whistles are often used instead. After the annunciation, whether by voice or siren, the blaster throws the switch or depresses a plunger to set off the blast. Or, in the good days, a third option would have been to strike a match or light a fuse! But what is going on here?
We know that we need an “initiator” to set off an explosive, something like a blasting cap for example. However, we also know that many of the blasting agents in common use today are not cap sensitive, and consequently, we need to use a primer. The cap, or whatever initiator we use, sets off the primer, which then sets off the blasting agent or explosive. Finally, you will recall that there are times when we are concerned that the explosion will not continue due to the length of the explosive column or the use of decking, for example, and in those cases, we add boosters. And in some cases, we will actually have multiple boosters in the hole.
We’ve talked at length about explosives. Now, let’s spend some time with initiators!