Abstract: An ignition device in the form of a linear member which has an internal linear propagation characteristic of a detonation, but a radial heat and gas evolution characteristic of a very fast deflagrating pyrotechnic material not accompanied by a shock or detonation wave. The device uses a central core containing an encapsulated explosive with a surrounding layer, or discrete layers, of a metal-clad pyrotechnic material that is significantly characterized by a class of compounds that are specific simple decahydrodecaborate salts containing the common anion B.sub.10 H.sub.10.sup.-2. The outer cladding materials themselves do not functionally ensure a radial deflagration; rather the specific pyrotechnic materials employed ensure a radial deflagration. There are taught specific relationships for components, and a necessary radial compaction.