Digital and Electronic Devices Design HygieneL indoor air monitoring system by Jiachun People spend 90% of their time indoor. However, the indoor air can be much more polluted than the outdoor. This will lead to sick-building syndrome, which includes asthma and other respiratory diseases. A betterway of showing the overall hygiene level is in demand. HygieneL system is designed for this. It has a shell-like sensor node for deploying. The circuit system is able to detect VOCs, CO2, RH and temperature which can be analysized. What's more, it also contains a visualization system for administrators to monitor the overall hygiene status in a building.