What is the thing on top of a hotel room that flashes red light ？

When everyone is out and about, they have stayed in hotels or guesthouses and often find a circular plastic object with a diameter of about 10 centimeters on the ceiling of the room. There is a red light flashing on top, and some people may think it is a camera, but it is not.

Cameras are usually installed in very concealed places, such as televisions. We just need to keep the room dark, turn on the flashlight on our phone, and go around the room to check for any abnormal reflective points. In fact, this kind of thing that people often mistake for a camera is called a "smoke detector" and is a type of fire protection device.

When a fire starts, a large amount of smoke will accompany it. This smoke will enter the smoke detector and be sensed. The device will automatically analyze the concentration of the smoke. If the concentration exceeds the set value, the device will trigger a fire alarm, and the small hole next to it will automatically spray water to put out the fire.