What is this device used for in my apartment?

It looks like a smoke detector or a motion sensor. Do you have an alarm system?

We have one, and it’s a motion sensor. The house is wired for security, but because we’re renting, we don’t have it turned on. It blinks anyway, whenever we move in the room.

Yes, it will blink when it senses movement. My motion sensor is activated at my alarm panel when the system is set for motion. If it’s triggered it alerts the central monitoring station.

It could be a carbon monoxide sensor.

Really? It is a motion sensor!

It’s a motion sensor.