For those of you installing/replacing your CO monitor- I believe they need to be located near the ground as CO is generally concentrated in lower areas. If you are just sticking them into your outlets at chest level (I'm short), you may not get the warning until you've already started feeling some of the effects of the gas or if you're sleeping, you might already be done by the time the alarm triggered so high from the floor.
I think this is why manufacturer places them low to the floor.
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