A fire extinguisher is a metal canister filled with chemicals that can put out small fires quickly. When you squeeze the handle, it shoots out foam, powder, or carbon dioxide that stops the fire from burning by cutting off its oxygen supply or cooling it down.

Fire extinguishers hang on walls in schools, offices, and kitchens because fires can start unexpectedly: a forgotten pan on the stove, a spark from faulty wiring, or a campfire that spreads too far. Having a fire extinguisher nearby means you can stop a small fire before it becomes dangerous. Different types work on different fires. A kitchen fire extinguisher handles grease fires, while others work better on electrical fires or burning paper.

Using one is straightforward. Many people remember the word PASS: Pull the pin, Aim at the base of the fire, Squeeze the handle, and Sweep side to side. Fire extinguishers only work on small fires, though. If flames are taller than you or spreading fast, the smart move is to get out and call 911 immediately.

The invention of portable fire extinguishers in the early 1800s saved countless lives and buildings. Before them, people relied on buckets of water or sand, which meant small fires could quickly become disasters.