The fire piston has been in use for a very long time. Its purpose is to light fire by creating heat. The purpose of this article is not to provide a background but to provide a basic explanation on how it works and why. The fire piston is comprised of four parts:
As we can see in the image on the right (source: Introduction To Chemical Physics, 1874, by Thomas Ruggles Pynchon, page 225) the mechanism is simple.  The piston is pushed into the tube in a rapid manner, as air cannot escape pressure builds up resulting in heat. In order for air to be properly compressed the piston is ever so slightly smaller in diameter from the tube and is wrapped near the bottom end (the part that enters the tube first) with rope or using a rubber o-ring (more wide spread today as it lasts longer) over a slight indent to prevent the o-ring/rope from loosning/moving; most times the o-ring/rope is lubricated using petroleum jelly / saliva prior to use to provide a tighter seal and ease pressurization. At the very tip of the piston there's a small hole/clip to place the tinder/charcoal cloth so that it will be present during the process and will light-up from the heat created (can be up to 800 degree's Fahrenheit). Ordinary use is simple (as described), lubricate the o-ring/rope, place tinder/charcoal cloth, very slightly insert the piston then with one swift strong push insert and remove the piston from the tube. Further reading: http://courses.umass.edu/plecprep/thermo/4b7010.html - High quality images of a lab fire syringe http://www.firepiston.com/ - Some modern fire pistons |
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Fire Piston |