One limitation of thermal imagers is that:

• A. They cannot detect fire through walls
• B. They are unreliable in any heat condition
• C. If a structure is carpeted, they may not be able to detect fire on the floors below
• D. They require direct flame contact to operate

Answer: (C)

Thermal imagers work by sensing infrared radiation emitted from surfaces and converting that into an image of heat patterns. What you see depends on a clear line of sight to a heat source and on the heat reaching a surface that the camera can “see.” When heat originates on a lower level, it has to travel through floors and any coverings to reach the surface on the level you’re looking at. Carpet adds insulation and absorbs heat, damping the infrared signal that could reach the detector above. That means a fire on a lower floor can be hidden or appear much weaker on an upper floor when viewed with a thermal imager, making it harder or impossible to detect initially.

Understanding this helps explain why carpeted flooring can mask fires on floors below—the barrier limits how much heat signature the camera can pick up. Other statements aren’t as relevant to this specific limitation: thermal imagers don’t require direct flame contact and aren’t unreliable in all heat conditions, and while they can’t see through walls, the point here is about how flooring and carpet impede detection of lower-floor fires.