A grease fire is a fire fueled by cooking oil or fat that has been heated past its ignition point. It burns hotter and spreads faster than most household fires, and it reacts violently to water, making it one of the most dangerous emergencies that can happen in a kitchen. U.S. fire departments responded to an estimated 170,000 home cooking fires in 2021, and cooking remains the leading cause of home fires and home fire injuries in the country.
How a Grease Fire Starts
Every cooking oil has a smoke point, the temperature at which it begins to break down and release visible smoke. Butter hits its smoke point at around 302°F, extra virgin olive oil at roughly 374°F, and refined canola oil at about 400°F. If the oil keeps heating past that point, it eventually reaches its flash point, where the vapors above the surface can ignite from a nearby flame or heating element. Heat it further still and the oil reaches its autoignition temperature, where it catches fire on its own without any spark at all.
The most common trigger is simple: leaving a pan unattended. Unattended cooking equipment is the leading factor in home cooking fires, responsible for 37% of cases. A pot of oil left on a burner at high heat can go from smoking to burning in under a minute, especially with lower-smoke-point fats like butter or lard. Overcrowding a pan with wet food can also cause oil to splatter onto the burner, and a thin layer of built-up grease on a stovetop can ignite from sustained heat.
Why Water Makes It Worse
The single most important thing to understand about a grease fire is that water will turn it into an explosion. This reaction is so violent and so counterintuitive that it causes serious injuries every year.
Here’s what happens: burning oil sits at temperatures well above 500°F. Water boils at 212°F. When even a small amount of water hits the surface of burning oil, it instantly converts to steam, expanding to roughly 1,700 times its original volume. That explosive burst of steam launches droplets of burning oil in every direction, creating a fireball that can reach the ceiling and spread the fire across the entire kitchen in seconds. The NFPA notes that this sudden expansion can throw burning oil all over the area, injuring people nearby and causing far more damage than the original fire.
This is also why you should never carry a burning pan to the sink. Moving it risks sloshing flaming oil onto your skin, your clothes, or nearby surfaces, and the instinct to run water over it will only make everything worse.
How to Put Out a Grease Fire
The correct response depends on the size of the fire, but the first step is always the same: turn off the heat source. Don’t try to move the pan.
For a small fire contained to the pan, slide a metal lid or a baking sheet over the top to seal it completely. This cuts off the fire’s oxygen supply, which it needs to keep burning. Don’t use a glass lid. The intense heat can shatter it, sending glass into the burning oil and creating a second hazard. Once the lid is in place, leave it there until the pan cools completely. Removing it too early lets oxygen rush back in, and the oil may still be hot enough to reignite.
Baking soda (sodium bicarbonate) also works on small grease fires. It disrupts the chemical reaction sustaining the flame and acts as a smothering agent. You need a significant amount, though. A light sprinkle won’t do much against an active fire. Salt works similarly in large quantities, but it’s a less effective option.
Never use flour. It looks like baking soda, but flour is combustible. Throwing it onto a grease fire can cause it to ignite in midair, turning a manageable situation into a much larger one. Sugar and other baking products carry the same risk.
Choosing the Right Fire Extinguisher
Not all fire extinguishers work on grease fires, and using the wrong one can make things significantly worse. The NFPA is direct on this point: extinguishers rated for Class K fires are the only type that should be used on cooking oil fires. Many other types will be ineffective or can cause an explosion.
A standard ABC dry chemical extinguisher, the kind most people keep in their kitchen, discharges its contents at high pressure. That force can blast burning oil out of the pan and scatter it across the kitchen, spreading the fire far beyond its original footprint. CO2 extinguishers carry the same risk. Class K extinguishers work differently. They dispense a wet chemical agent at lower pressure to avoid disturbing the oil’s surface. The agent forms a foam blanket over the grease that smothers the fire and prevents reignition, while its water content gradually cools the oil below its autoignition temperature.
For home kitchens, a Class K extinguisher is the safest choice if you want one specifically for cooking fires. They’re more expensive than standard models but designed for exactly this scenario.
After the Fire Is Out
Once the fire is extinguished, resist the urge to immediately clean up or inspect the damage. If you smothered the fire with a lid, leave the lid in place until the pan has cooled to room temperature. This can take 30 minutes or longer depending on how much oil was in the pan. The oil remains dangerously hot well after the flames disappear, and removing the lid prematurely risks reignition.
If the fire spread beyond the pan, even briefly, check the surrounding area carefully. Grease fires deposit a fine layer of oil on nearby surfaces, cabinets, walls, and range hoods. This residue is itself flammable and should be cleaned thoroughly before you use the stove again. If the fire triggered any structural damage, discolored the ceiling, melted fixtures, or scorched cabinetry, have the area inspected before resuming normal cooking.
Preventing Grease Fires
Most grease fires are preventable with a few habits. Stay in the kitchen when heating oil, especially during deep frying or pan-searing. Use a thermometer to monitor oil temperature rather than guessing. If you see smoke rising from your oil, it’s already close to its flash point. Turn down the heat immediately or remove the pan from the burner.
Keep the stovetop clean. Built-up grease on burners, drip pans, and range hoods provides fuel for a fire even if the pan itself isn’t the problem. Pat food dry before placing it in hot oil, since moisture causes splattering that can ignite on contact with a flame. And keep a metal lid within arm’s reach whenever you’re cooking with oil. It’s the simplest, most reliable tool for stopping a grease fire before it grows.