A fire piston, sometimes called a fire syringe, or a slam rod fire starter, is a device of ancient origin which is used to kindle fire. It uses the principle of the heating of a gas (in this case air) by its rapid compression to ignite a piece of tinder, which is then used to set light to kindling.
A fire piston consists of a hollow cylinder ranging in length from about 3 to 6 inches, having a bore about 0.25 inches in diameter, sealed at one end and open at the other. A piston with an airtight circular seal is fitted into the cylinder. The piston has a handle on the end to allow a firm grip to be applied to it, or a large enough surface area to strike it sharply without causing pain while the cylinder is braced against a hard surface, and it can be completely whithdrawn from the cylinder. The piston generally has a notch or recess on or in its face, into which a piece of tinder is placed.
The compression of the air when the piston is quickly rammed into the cylinder causes the interior temperature to rise sharply to 260°C (500°F). This is hot enough for the tinder or in the piston face to ignite with a visible flash that can be seen if the cylinder is made of translucent or tranparent material. The piston is then quickly withdrawn, before the now-burning tinder depleates the available oxygen inside the cylinder. The smoldering tinder can then be removed trom the face of the piston and transferred to a larger nest of fine kindling material. The ember is then fanned or blown upon vigorously to create a flame, at which time various stages of larger kindling can be added until built into a proper fire.
Ancient and modern versions of fire pistons have been made from wood, animal horns, antlers, bamboo, or lead. Other metals have also been used in modern versions.