Human detection equipment that operates indoors and outdoors plays an important role in modern security applications. We describe a nonconventional system to detect thermal infrared radiation from relatively hot objects using a conical horn and a non-matrix thermal infrared sensor. It is shown that using a conical horn as a radiation concentrator in a recording device is preferable to a focusing lens due to specific differences between them. A software program in Python is developed to permanently observe the thermal infrared radiation from surroundings. The obtained results indicate an inverse relationship between the angle of view and the gain level of conical horns. It is experimentally shown that the horn-sensor pair detects humans at long distances (up to 40 m) with a relatively narrow angle of view of 16 deg. On the other hand, using a conical horn with a wider apex angle increases the angle of view of the recording system up to 30 deg but reduces the detection range. The device with four coupled horn-sensor pairs extends the horizontal angle of view to 90 deg. The developed technique can operate day and night, indoors (including observation of long corridors), and outdoors to monitor humans and vehicles or to prevent fires. The recording system can be applied together with other security equipment as an initial alarm system that triggers video monitoring and night vision devices.