Which of the following materials can ignite during secondary fires?

Secondary fires can occur when materials that are not directly involved in a primary fire become ignited as a result of heat, embers, or flames from the initial combustion event. Wood is a combustible material that readily ignites when exposed to sufficient heat sources, making it a common candidate for ignition during secondary fires.

Both paper and wood are flammable, but wood typically signifies a larger, more durable source of fire risk in the environment, particularly in structures or outdoor settings where secondary fires may spread easily. In contrast, glass and stone are non-combustible materials and do not ignite or contribute to a fire. Understanding the behavior of these materials in fire scenarios is crucial for fire safety measures and fire prevention strategies.