Can Anyone Recognize This Smoke (?) Detector?

The item I have in my house is either a smoke detector (or carbon monoxide detector). It started to chirp so I think I will need to change the battery. However, I cannot open the item or take it out. The brand is not even recognizable so I have to Google the instructions.

This item was included in the purchase of our home two years back. I have emailed its former owner to find out when he will get back to us. Any of you could help me, thank you!