"The energetic material used often called pyrogen is usually a pyrotechnic composition made of fuel and oxidizer where the produces significant amount hot particles that cause/promote ignition desired material. Initiator compositions are similar to flash powders but they differ in burning speed as explosion not intended have intentionally high production particles. They also tend be easier ignite than thermites with which share similarities. Common oxidizers used potassium perchlorate nitrate. fuels titanium titanium(II) hydride zirconium zirconium boron. The size determined produce required time. More exotic materials can e.g. carboranes.1 For special applications pyrophoric igniters burst into flame contact air. Triethylborane/TEA-TEB was an igniter for Lockheed SR-71 jet engines Rocketdyne F-1 engine on first stage Saturn V NPO Energomash's RD-180 Atlas SpaceX's Merlin Falcon 9."