Safety Officer’s Note: Carbon monoxide is odorless. Propane is also odorless but a scent is added to the gas so that detection can be made for fire safety. Carbon monoxide is a byproduct of propane that does not fully combust, or turn to flame. The leak in the ventilation brought in another more deadly gas, carbon monoxide. As most of us would have, they thought the smell was a normal scent from an outside generator working away; the smell of propane should have been a red flag for the parents, and I know it will be next time!