Which of the following is NOT a main type of diagram?

A reconstruction scheme is often utilized in the context of fire investigations to develop theories about the sequence of events or to visualize how an incident may have unfolded. However, it is not classified as a primary type of diagram in the same way that site plans, floor plans, and exploded views are.

Site plans provide a broad view of the premises, detailing the layout of buildings and surrounding features, which helps investigators understand the context of the fire or incident in relation to its environment. Floor plans give a detailed look at the interior layout of a specific structure, showing walls, doors, and possibly furniture, which is vital for analyzing the dynamics of the fire spread and potential escape routes. Exploded views break down components into a three-dimensional representation, making it easier to visualize complex systems and their relationships, particularly useful in understanding mechanical failures or constructions.

The other options represent mainstream, foundational diagrams that are commonly used in fire investigations, which distinguish them from the reconstruction scheme.