Andy M.
Certified Pretend Chef
Smoke Alarms are best fitted on ceilings whereas Carbon Monoxide alarms are best on the wall at average head height of the occupants per <that post on Quora. There are more posts that go into more detail, if you're interested.
Our silly ceilings are only 7 1/2 feet. Himself is 6' 2" in bare feet. It doesn't matter much in our house!
Interesting. Our CO detectors came with instructions to install them about two feet off the floor. Makes sense. CO is heavier than air and would accumulate at floor level first.