3 Use a Class B fire extinguisher. As with electrical fires, water-based (Class A) fire extinguishers should not be used on liquid or oil fires. Carbon dioxide (CO2) and dry chemical fire extinguishers will have a Class B rating.[23] Check the label on the extinguisher and ensure that it says Class B before using it on a flammable liquid fire.
• To use the extinguisher, pull any pin stopping you from depressing the handle, point the horn at the base of the fire, and hold down the handle.[24] As you see the flames shrinking, approach the source and continue spraying until the fire is fully extinguished.[25]
• If you cannot extinguish the fire within five seconds of using the extinguisher, then it’s too large.[26] Evacuate to a safe place and call 911.
• The only exception to this rule when the liquid fire stems from vegetable oil or animal fats in commercial-size deep fryers and other restaurant equipment. The large size and extreme heat and fuel source of these devices get their own classification for fire extinguishers—Class K extinguishers.[27] Restaurants with this type of equipment are legally required to keep a Class K extinguisher present.[28]
• Do NOT throw water on liquid or oil fires. Water does not mix with the oil. When they are together, the oil stays on top of the water. The water will then boil and become steam 'very quickly.’ This quick boil is dangerous. Since the water is on the bottom of the oil, it sprays hot, burning oil in every direction as it boils off and evaporates. This then spreads the fire very quickly.