There are many factors that affect TVOC readings.When we go to sleep at night, we usually close the doors and windows and stop walking around. This reduces the circulation of air and makes the readings higher than during the day.In addition, the sweat produced during sleep, and the exhaled gas also contains a variety of VOCs, which also increases the concentration of TVOV.Even the TVOCs that are distributed in furniture and decoration materials are more obvious at night because they are not ventilated.