What are PIR alarms useful in tracking?

• A. An intruder's progress through a location
• B. The intruder's general location
• C. Movement of vehicles outside
• D. Temperature changes in the area

Answer: (A)

PIR alarms work by sensing changes in infrared radiation when a warm body moves within their field of view. Because they respond to motion, they’re best for showing how someone moves through a space—where they go, and in what order—so you can trace an intruder’s progress as they pass from one zone to another. That movement-based detection lets you piece together a path through a building or area, which is the core usefulness in tracking.

They don’t give a single, precise general location at once, and they aren’t designed to track vehicles outside or to measure temperature changes. A vehicle might not trigger the same way as a human moving through a corridor, and PIR sensors don’t monitor ambient temperature; they only flag changes in infrared radiation caused by moving heat sources.