Speaking of carbon monoxide, I visited the Sedna IV (german boat used by Jean Lemire and his team for making documentaries about global warming in Arctic and Antartica) and there's a special carbone monoxide button to press in case of fire emergency inside the lower rooms. It's heavier than air and will smother the fire (people must of course evacuate the rooms before). It was interesting to see that everything on board had at least 3 back up alternatives in case of failure. They have to live on their own for months so it was an interesting lesson from a survival perspective.