This device is designed for securing big spaces, like: production halls, wearhouses, museums, shopping malls etc. Beam smoke detector monitore wide area in the range of 8 - 100 [m]. Device consist of transmiter and reciver mounted in the same housing, and mirror. Transmiter sends infrared beam which reflects of the mirror and goes back to the reciver. In case when beam is disturbed by smoke,  detector activates alarm.