A small thin-walled cylindrical case contains a sensitive explosive. Blasting caps serve as initiators of explosive charges. They consist of a cylindrical copper or aluminum capsule containing a primary charge of an initiative explosive or a mixture of initiating explosives (e.g. lead azide with lead trinitroresorcinate), in order to achieve a higher brisance, they also contain a secondary charge of high brisance explosive (e.g. Tetryl, PETN, Cyclonite).

A blasting cap can be ignited by the flame of a safety fuse or electrically, or no electrically as in the case of shock tube.

In the past, 10 standard types of blasting caps were marketed, these differed from each other by the quantity of the explosive in the charge and by their size. Currently No.8 blasting cap (0.3 g primary charge, 0.8g secondary charge, 4-50 mm in length and 7.0 mm in external diameter) is, for all practical purposes, the main type of blasting cap on the market.