The First Alert SC05CE detects both smoke and carbon monoxide. When the smoke and carbon monoxide detector detects smoke or carbon monoxide, it produces an alarm with an 85-decibel audio signal. You can't miss it. The 2-in-1 detector runs on AA batteries, so you can place it anywhere in your home. To be sure that the detector is working, test it regularly using the test button. When the batteries are almost empty, the detector will tell you by producing a loud beep. It's then up to you to change the batteries as soon as possible.
Before you mount the detector, decide what you want it to detect, because that determines whether you install it against the ceiling or the wall.