The infrared detector works by detecting the infrared radiation emitted by the human body. The detector collects external infrared radiation and then focuses it onto an infrared sensor. The infrared sensor typically uses a pyroelectric element. When this element receives infrared radiation, it releases charges when there is a change in temperature, and after detection and processing, an alarm is triggered. In other words, as long as you're not detected by the infrared, you're fine.
In the dark of night, infrared is invisible and difficult for the naked eye to distinguish. Ordinary people would inevitably be discovered and exposed upon entering. Fortunately, Luo Zheng and his team were wearing specially made tactical glasses with infrared detection capabilities, allowing them to see infrared in the darkness. Otherwise, they would have walked right into it.
