A fire blanket is a safety device designed to extinguish small incipient (starting) fires. It consists of a sheet of fire retardant material which is placed over a fire in order to smother it (see below).
Small fire blankets, such as for use in kitchens and around the home, are usually made of fiberglass and sometimes kevlar, and are folded into a quick-release contraption for ease of storage.
Larger fire blankets, for use in laboratory and industrial situations, are often made of wool (sometimes treated with a flame retardant fluid). These blankets are usually mounted in vertical quick-release container so that they can be easily pulled out and wrapped round a person whose clothes are on fire.
Some older fire blankets were made of woven asbestos fibers and are not NFPA rated. This can pose a hazard during the decommissioning of old equipment.
In order for a fire to burn, all three elements of the fire triangle must be present: heat, fuel and oxygen. A fire blanket either completely surrounds a burning object or is placed over a burning object and sealed closely to a solid surface around the fire. Whether the blanket is placed on top, or surrounding it, the job of the blanket is to cut off the oxygen supply to the fire, thereby putting it out.