Which factors can cause a PIR false alarm?

• A. Only moisture
• B. Only motion
• C. Heat sources such as sunlight, central heating
• D. None of the above

Answer: (C)

Passive infrared sensors detect changes in infrared energy (heat) in their field of view. When a heat source such as sunlight hitting the detector or radiant heat from central heating, heaters, or other warm objects creates changing infrared patterns, the sensor can misinterpret that as motion and trigger a false alarm. Moisture isn’t typically what these sensors respond to, and motion would be an actual trigger if there were a real moving warm body—so it’s not considered a false alarm factor. In short, heat sources like sunlight and central heating are the most common causes of PIR false alarms.