They are somewhat similar to blasting caps or other detonators, but they differ in that there is no intention to produce a shock wave.
The energetic material used, often called pyrogen, is usually a pyrotechnic composition made of a fuel and oxidizer, where the fuel produces a significant amount of hot particles that cause/promote the ignition of the desired material.
Initiator compositions are similar to flash powders, but they differ in burning speed, as explosion is not intended, and have intentionally high production of hot particles.
[1] For special applications, pyrophoric igniters can be used which burst into flame in contact with air.
BPN's high temperature makes it suitable for uses where rapid and reproducible initiation is critical, e.g. for airbags, rocket engines, and decoy flares.
[7] Formation of an intermetallic compound can be a strongly exothermic reaction, usable as an initiator.
Titanium-boron composition is one of the hottest pyrotechnic reactions in common usage.
It can be used as a pyrotechnic initiator or for heating confined gas to perform mechanical work.
[9] The reaction is initiated by heat, typically supplied by electric current pulse.
The reaction begins at 600 °C, the melting point of aluminium, and proceeds violently to temperature of 2200–2800 °C.
Pyrofuze foils can be used for e.g. sealing of various dispensers or fire extinguishing systems.
[14] BNCP, (cis-bis-(5-nitrotetrazolato)tetraminecobalt(III) perchlorate) is another common initiator material.