A fire blanket smothers a fire by cutting off its air. It has two proper uses in an ordinary building: a small contained cooking fire, and a person whose clothing is alight. It is not a general purpose firefighting tool and it is dangerous if used on a fire too large for it, because using one means standing over the fire.
How it works
The blanket is a woven glass fibre sheet that will not burn at cooking fire temperatures. Laid completely over a fire it excludes air from the fuel, and the fire goes out when the oxygen under it is used up. Nothing else happens: there is no cooling to speak of, which is why a pan must be left covered and left alone rather than uncovered to check.
The two real uses
A small contained cooking fire, typically a pan, where the blanket can cover the whole thing with margin around it. And clothing on fire, where the blanket is wrapped around the person after they have been got to the ground, which is the stop drop and roll advice with a blanket added. In both cases the fire is small, contained and close.
The technique
Pull both tapes down sharply to release it. Hold it by the top edge with the fabric hanging down so it shields your hands and forearms, and keep your hands behind it throughout. Approach from the near side of the pan and lay the blanket across and away from you so it covers completely, never drop it from above or throw it. Turn the heat off if the control is reachable without leaning over the pan.
Afterwards
Leave it in place for a long time. Cooking oil holds heat for far longer than people expect and lifting the blanket to look admits air to fuel that is still above its ignition temperature, which relights it in your face. Leave the room, let it cool, and do not move the pan. A blanket that has been used on a fire is discarded, not folded back into its case.
Questions people ask about fire blanket
What type of fire is a fire blanket used for?
A small contained cooking fire, and clothing that is alight. It is not a general firefighting tool and it should never be used on a fire too big for the blanket to cover completely.
How does a fire blanket work?
By excluding air. Laid completely over a fire it cuts off the oxygen supply. It does almost no cooling, which is why the covered pan has to be left alone for a long time.
Can a fire blanket be reused?
No. A blanket that has been used on a fire is disposed of. Some are also marked for single use even after a training deployment, so check what yours says.