How PIR motion sensor technology works, can it detect real motion of an object, heat from a fire or just human body temperature:
PIR stands for ‘Passive Infra Red’. The sensor itself does not emit energy (that is why call “passive”), but it can detect an infrared emitting source with one temperature such as human body that passes in the front of a source with another temperature such as a wall. PIR cannot detect non-temperature object or real motion of an object moving in the front of the sensor. (If a sensor sends out ultrasonic waves/microwaves and detects the reflection off a moving object, then it is ACTIVE).
It is not to say that the sensor detects the heat (different with heat sensor) from the object passing in front of it but that the object breaks the field which the sensor has determined as the “normal” state. PIR sensor is set to detect rapid temerature change which means that it works in case of intrusion (human) and fire. Fire can also be detected by other types of sensors such as Heat Sensor by means of temperature or sudden temperature change that break its preset temperature (not by means of infrared), Smoke Sensor by means of smoke or sudden increased of smoke blocking the light-beam in the smoke sensor (not carbon dioxide), and etc. Most of our PIR motion sensors (SM-80, DigiAir-SD) are pet immunity to avoid false alarm (under 10kg/22lb).