Is carbon monoxide heavier than air? What is the diffusion of carbon monoxide in air?

Carbon monoxide is not heavier than air. The diffusion of carbon monoxide in air is relatively even, meaning that a source of carbon monoxide can distribute the gas evenly throughout the room and house. When installing a carbon monoxide alarm, choose a location where the alarm will stay clean, and out of the way of children or pets. See User's Manual for specific installation requirements.