Which factor favors the selection of shelter-in-place as a protective action?

The selection of shelter-in-place as a protective action is particularly favored in scenarios involving a slow-moving airborne contaminant. This is because sheltering-in-place allows individuals to effectively shield themselves from exposure by staying indoors where air is less likely to be contaminated. In contrast, a fast-moving airborne contaminant presents a situation where the material can rapidly spread to different areas, making it less effective for individuals to find a safe location after being exposed. By the time people realize the threat, they may already be in the path of the contaminant.

Factors such as a long-duration incident or the storage of chemicals indoors may require different responses, such as evacuation, depending on the immediate risk and the potential for exposure. However, the defining characteristic that supports shelter-in-place is the nature of how the contaminant behaves in the environment and the time available for individuals to respond.