A grease fire occurs when cooking oil or fat overheats and ignites, typically within a kitchen. These fires can escalate rapidly and present a significant hazard. Flour should never be used to extinguish a grease fire, as it can worsen the situation.
The Danger of Using Flour
Flour is a combustible material, and its finely powdered form poses a serious risk when exposed to an open flame. When thrown onto a grease fire, it disperses into the air, creating a cloud of tiny particles. This increases its surface area, allowing rapid reaction with oxygen.
This dispersed cloud can ignite instantly, leading to a dust explosion. For cereal flours, the Lower Explosive Limit can range from approximately 20 to 63 grams per cubic meter. Instead of smothering the fire, flour becomes a fuel source, causing a sudden expansion of flames. Flour does not absorb oil or cool the burning substance, making it ineffective for extinguishing grease fires.
Effective Ways to Extinguish Grease Fires
To extinguish a small grease fire, cut off its oxygen supply. First, turn off the heat source if safe. Then, carefully slide a metal lid or cookie sheet over the pan to smother the flames. Use a metal lid, as glass can shatter under extreme heat. Leave the lid in place until the pan and contents have cooled to prevent reignition.
For very small grease fires, use a large amount of baking soda. Baking soda releases carbon dioxide when heated, displacing oxygen to smother flames. Apply enough baking soda to completely cover the burning area. Never use baking powder or flour, as they can worsen the fire.
A fire extinguisher can be used if other methods are insufficient. Class K fire extinguishers are designed for cooking oil and fat fires, often found in commercial kitchens. These extinguishers work by saponification, forming a soapy foam that cools the oil and prevents reignition. For home use, a Class B or multi-purpose Class B/C extinguisher is appropriate for flammable liquids like grease.
Never use water to extinguish a grease fire. Water is denser than oil and sinks beneath the burning oil. The intense heat causes water to instantly vaporize into steam, expanding violently. This rapid expansion can propel burning oil droplets into the air, spreading the fire and potentially creating a dangerous fireball.
Preventing Grease Fires
Preventing grease fires requires attentive and safe cooking habits. Unattended cooking is a leading cause of kitchen fires; always remain in the kitchen when frying or cooking with oil. Grease fires can ignite in as little as 30 seconds.
Keep flammable items, such as dish towels, oven mitts, and curtains, away from the stovetop. Regularly clean grease buildup on cooking surfaces, as accumulated grease can catch fire. When cooking, use a pan appropriate for the size of the burner and avoid overfilling pots with oil.
Monitor oil temperature carefully. If oil begins to smoke, it is too hot and nearing its ignition point; immediately turn off the heat. Most vegetable oils have a smoke point around 450°F, while animal fats typically start smoking around 375°F. Blot excess moisture from food before adding it to hot oil to prevent splattering.