Beam detectors are devices that use infrared beams to detect smoke obscuration. When the smoke causes the beam strength to drop a set amount, the device will enter an alarm state, setting off the fire alarm system. Beam detectors are used to cover large areas or hard to access areas.
![Beam Detector](https://i0.wp.com/firealarmsboston.com/wp-content/uploads/2013/04/6500-MMK.jpg?resize=640%2C640)