PIR detectors sense temperature changes, that is, changes in infrared radiation. But there are other factors, such as light and temperature changes in the working place, which can affect the sensitivity of the detector. Interference factors such as: 1. Light interference: sunlight from windows, car headlight beams; 2. Overall temperature changes; 3. Fax : Paper spit out from a hot fax machine; 4. Objects: shaking curtains or blinds just after sunlight; 5. Animals: mice, birds, cats or dogs; 6. Air flow: from windows, heaters Or the heat of the air conditioner or the cold air.