Which condition in a storage area increases the risk of spontaneous combustion?

• A. Dry cardboard boxes
• B. Empty pallets
• C. Oily rags left in a bin
• D. Metal shelving

Answer: (C)

Oily rags left in a bin create a high risk of spontaneous combustion because the oil on the fabric can oxidize slowly, generating heat. If that heat accumulates in a closed or poorly ventilated bin, the temperature can rise until it reaches the rag or surrounding material’s ignition point, causing a fire without an external flame or spark. Dry cardboard boxes can burn if exposed to heat, but they don’t typically heat themselves through oxidation to reach ignition in normal storage conditions. Empty pallets and metal shelving don’t provide the same self-heating risk; metal is noncombustible, and empty pallets aren’t sources of heat generation. The key idea is that oily waste can self-heat and ignite if not properly contained and ventilated. To prevent this, store oily rags in approved closed metal containers, keep them away from heat sources, and ensure good housekeeping.