AC1215 comes With the light sensor, the air purifier is working according to the ambient light. When ever ambient light dims / increases for 10 seconds , all the lights on the control panel will be off or On slowly. During this period, you can touch any of the buttons, all lights will be on again. If you don't perform other operations within 10 seconds, all lights will be off. After the ambient light becomes bright and lasts at least for 10 seconds, all lights will be on again.
This information is also available in user manual