Excelsior found at a fire scene could indicate which type of ignition source?

The correct choice highlights that Excelsior, which is a type of wood wool or packing material, can be associated with the use of a trailer as an ignition source. In fire investigation terminology, a trailer is a substance that is intentionally spread to help fire spread from one area to another, effectively fueling the fire.

When Excelsior is present at a fire scene, it may suggest that someone used it to transport the flames across a specific area, potentially indicating a deliberate act of arson. The presence of this material can mean that the fire was not spontaneous; instead, it had been facilitated by an external factor. This is critical during fire investigations, as identifying such materials can reveal intentions behind the fire's ignition.

On the other hand, pyrotechnics generally refer to fireworks or similar items designed to produce visual effects through combustion, while fire detectors are designed to sense fire and do not ignite flames themselves. Accelerants are substances that can speed up the combustion process, but Excelsior specifically points more towards the method of spreading fire rather than an accelerant's role. Thus, the link between Excelsior and trailers solidifies its relevance in identifying ignition sources at fire scenes.