Which item is not listed as a potential cause for PIR false alarms?

• A. Heat/air
• B. Sunlight
• C. During active construction
• D. Loose screws

Answer: (C)

PIR sensors work by detecting changes in infrared energy within their field of view. They’re designed to ignore steady heat sources and only trigger when a warm body moves across the area, or when a new heat source causes a noticeable change in the infrared pattern. That’s why common nuisance triggers include heat from HVAC or heaters, sunlight heating part of the lens, or a loosened mounting that lets the sensor tilt and suddenly see a new IR source.

The option describing active construction isn’t typically listed as a PIR false alarm cause because construction activity itself doesn’t inherently create the infrared energy changes these sensors respond to. Dust, vibration, or other construction factors can affect other parts of a system, but they don’t usually produce the infrared changes that would falsely trigger a PIR.