In the two-part marking system for indicating which rooms have been searched, which symbol means a search is presently under way in a particular room?

The symbol that indicates a search is presently underway in a particular room is represented by a slash, which is one line of the letter X. This marking is part of a standardized system used by firefighters to quickly communicate the status of searches within a structure.

When firefighters enter a building to conduct searches, they use this marking to signify that an active search is occurring. This helps other firefighters and incident commanders understand where resources are being utilized and ensures that no areas are overlooked. The slash marking is clear and easy to recognize, making it an effective way to convey important operational information quickly.

In contrast, other symbols in the marking system serve different purposes. For example, a circle with no line through it typically indicates that a room has been searched and is clear, while a one-headed arrow might denote entry or exit pathways. A horizontal line with no slash usually signifies that a room is off-limits or that it's been checked but is not currently being searched. Thus, the choice that indicates an ongoing search—using the slash—provides clarity and security in a rapidly changing and potentially dangerous environment.