Carbon Monoxide Alarm to a Propane/ Carbon Monoxide Alarm

X2 on where danger comes from (lighter than =raises and heavier than air= low spots) but something else. WE redid ours last summer and I actually read the directions. My new one says of replace 5 years OR FROM date of manufacture. And was over one year old all ready, out of the box. Manufacture date is stamped on rear. So if you have a choice can get one that hasn't been sitting on a warehouse for a year already. And I was sort of stuck using the same location because of mounting holes.