The nose or mouth will appear cooler as the subject is inhaling and warmer as he or she exhales, since exhaled air is at core body temperature, which is several degrees warmer than skin temperature.

• 当采集对象吸气时，其嘴部或者鼻子处将会显示冷色的，而呼气时则会显示暖色的，这是因为呼出的气体来自体内，其温度要高于皮肤温度。