🔍 Key Concepts

• spontaneous combustion and how it happens • storage of oil‑soaked rags, metal turnings, and metal powders • role of air circulation, heat build‑up, and contamination with oil/grease

💭 Think About

• Think about which materials can slowly heat up by internal chemical reaction without an external flame or spark. • Consider what happens if oily materials or fine metal particles are piled together in a confined, warm space. • Ask yourself which options involve absorbent or finely divided materials that can trap heat and promote oxidation.

✅ Before You Answer

• For each choice, ask: can this material oxidize and heat up on its own under normal storage conditions? • Consider whether oils, greases, or other combustibles are present or could soak into the material. • Think about whether fine shavings or powders have more surface area, making them more likely to react and heat up.