"Grease fire" is the phrase firefighters use for most kitchen fires, so it surprises people to learn that grease does not technically count as flammable. The distinction matters less than what it does at 600 degrees.
Grease is combustible. Cooking grease (bacon fat, beef tallow, lard, and the residue that collects on a stove) will not ignite at room temperature, but heated past roughly 600°F it ignites from a flame, and past 700°F it ignites by itself. It burns hot, spreads if it moves, and reignites when the lid comes off too soon. Mechanical grease for bearings and hinges is far harder to ignite but will burn in an established fire.
Cooking Grease
Animal fats and the oils they render into behave the same as cooking oil. A pan of bacon on high heat with the fat pooling can go from sizzling to smoking to burning in a couple of minutes if nobody is watching. Deep fryers and turkey fryers are the same story at larger scale. The rules are the ones we repeat on every kitchen fire call: burner off, lid on, no water, don't carry the pan. The full walkthrough is in is cooking oil flammable.
The Hidden One: Grease Buildup
The grease fire that catches people off guard isn't in a pan. It's in the range hood filter, on the back of the stove, inside the oven, and on the wall behind the cooktop. That film of old cooking grease is fuel sitting right next to the burners. A flare-up from a pan can ignite the hood, and a hood fire can go into the duct and up into the ceiling. Restaurant kitchens have suppression systems for exactly this reason. At home, degrease the hood filter monthly and the surfaces around the stove regularly.
Grease Traps, Drains, and Trash
Pouring hot grease down the drain clogs pipes and, in a dryer vent or a shared wall cavity, can create a fuel source you never see. Let grease cool and solidify in a can, then throw it out. Don't put a hot grease can in a plastic trash bag.
Mechanical Grease
Bearing grease, lithium grease, and chassis grease are petroleum-based with a thickener, and they have flash points typically above 350 to 400°F. A tube of it in the garage is not a fire hazard. Grease-soaked rags and shop towels are, because oxidizing oil in a pile generates heat. Dry them flat or store them in a sealed metal can.
Quick Reference
| Grease | Ignites at room temp? | Burns when heated? | Main risk |
|---|---|---|---|
| Bacon fat, lard, tallow | No | Yes, ~600–700°F | Unattended pan |
| Range hood / stove buildup | No | Yes | Flare-up spreads to hood and duct |
| Bearing / lithium grease | No | Yes, in an existing fire | Soaked rags self-heating |
Related reading: where most house fires start and will salt put out a fire.
