A fire extinguisher is a sturdy metal cylinder filled with water or extinguishing materials. When the pull rod at the top of the cylinder is pressed, the high pressure forces the extinguishing agent inside to be ejected, similar to how a spray canister releases material.

In this fire extinguisher, a plastic tube extends from the bottom of the gas cylinder to the top of the extinguisher. A spring-loaded control valve blocks the passage from the tube to the nozzle. At the top of the cylinder, there is a slightly smaller cylinder filled with compressed gas—such as liquid carbon dioxide. The release valve prevents the leakage of compressed gas.

To use the fire extinguisher, pull the safety pin and press the operating lever; the operating lever pushes the actuating rod, which compresses the spring-loaded control valve at the bottom to open the nozzle passage; the pointed tip at the bottom of the actuating rod pierces the pressure release valve of the gas storage cylinder.

The release of compressed gas exerts a downward pressure on the extinguishing agent. This pressure is substantial, capable of propelling the extinguishing agent through a tube to the nozzle. The correct method of using a fire extinguisher is to aim it directly at the fuel source, not the flames themselves, and to sweep back and forth in a sweeping motion, directing the extinguishing agent flow downward.