In a "serious" fire you should ignore the fire extinguisher get everyone out of the building.
Fire extinguishers are for small fires! If a little oil in your frying pan catches on fire and you don't have a lid readily available to smother it, use a fire extinguisher. But if your smoke alarm wakes you up and you discover your whole kitchen on fire, get out. The fire extinguisher will not help in that situation, and it may cause you to waste time. (Tip: If and only if the fire extinguisher is easily available, carry it with you as you exit. You might need it to use it clear a path to get out.)
A fire extinguisher is to clear a safe path to the exit if the fire blocks it. never put them by the exit door as I see so many people do (in their garrage)
they can also be used on small fires but only if there is a safe escape route. (This is probably the most common use but not the primary use)
99% of the benefit of putting the extinguisher by the exit door is that it helps draw panicking people to the exit door. Which gives them another saving throw against Heroic Idiocy, at +4 - "Should I grab this totally unfamiliar little fire extinguisher and carry it back toward the big scary fire, to do something I've never even tried doing? Or should I just run out the handy exit door that I'm right next to?"
That's right, the best is to have a watered dishcloth that will suffocate the fire, hence stopping it. The fire extinguisher may be a bad idea because the pressure will spread burning oil around across the kitchen and the water is definitively the worse idea because it will counterintuitively make a bigger flame and also spread burning oil.
That works, but be sure to use a wool or cotton cloth.
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The proper method to deal with an oil fire: turn off the heat and smother the fire with a metal lid, metal baking sheet, or wool/cotton cloth. Do not use a fire blanket made of polyester or nylon; it will melt and burn producing toxic smoke. Do not use flour or any other flammable/explosive powder. Do not use water, as the liquid water will get into the oil and expand 1600 times its original size as it turns to steam; this rapid expansion will fling burning oil everywhere. If you do use an extinguisher, be careful not to spread the burning oil.
For small NON-OIL, non-electrical fires, smothering with a wet non-synthetic cloth is the best way to stop the fire.
Fire extinguishers are for small fires! If a little oil in your frying pan catches on fire and you don't have a lid readily available to smother it, use a fire extinguisher. But if your smoke alarm wakes you up and you discover your whole kitchen on fire, get out. The fire extinguisher will not help in that situation, and it may cause you to waste time. (Tip: If and only if the fire extinguisher is easily available, carry it with you as you exit. You might need it to use it clear a path to get out.)