At the top of the hotel, two green lights will be on for 20 seconds. Is it a camera?

This is not a camera. This thing is called a smoke detector. This is a fire extinguishing device. You can feel the concentration of smoke in the air. When a fire breaks out, it is usually accompanied by light, heat and smoke. At the beginning of the fire, due to the low temperature of combustion products and smoldering state, a lot of smoke will be produced.

When the smoke enters the smoke detector, it will be detected by the smoke detector and its concentration will be analyzed. When the concentration exceeds the set value, it will trigger a fire alarm. Cameras are usually installed in very hidden places, such as under the TV. We just need to keep the room dark, turn on the flashlight and check whether there are abnormal reflection points around the room.