Bests & Worsts Reviews from Amazon

Not the easiest clam-shell to get into, but once in, minimal packaging. Comes with the 9v back-up battery. I was a little concerned, when I plugged it in, the red-light came on, and I thought "oh that is odd... red is an alarming color... do I have Carbon Monoxide in my house?" but No. Rest assured, the "red" light is the power light, and also blinks once per minute (and chirps) when your 9v battery gets low. Red solid light is the normal "I am on and doing my job" status indicator light. If you detector is alarming it will flash red constantly, and beep like CRAZY! can't be ignored, unless you are deaf, but then you get the visual cue. I admit, this is all in the instructions, but I didn't read the instructions until I was alarmed by the red light.