What do the green, amber, and red VOC sensor indicator lights mean?

The VOC sensor indicator lights reflect the level of Volatile Organic Compounds detected in the room: green means a low level of VOCs is detected and the unit operates on the LOW setting, amber means a moderate level is detected and the unit operates on MEDIUM, and red means a high level is detected and the unit operates on HIGH. The air purifier will continuously monitor VOC levels and adjust the cleaning level automatically. (Page 6)