Low oxygen shut off is of course very important. But just having plenty of oxygen available, through leaky windows and boards or whatever is only part of what you need to worry about when you are burning anything in an enclosed space. Carbon Monoxide, AKA CO, will kill you even when there is plenty of oxygen available. And it can kill you slowly enough that you don't even notice. This is because CO sticks better to the hemoglobin in your blood than oxygen. Hemoglobin is what carries oxygen in your blood and delivers it to the rest of your body. Carbon Monoxide, since it sticks to hemoglobin better than oxygen, will crowd out the oxygen in the air you are breathing. And it doesn't let go easily. This means it builds up in your blood over time, whereas oxygen doesn't. So if enough CO is present in the air you are breathing it will eventually bind to enough of your hemoglobin to suffocate you, even though there is a normal amount of oxygen in the air you are breathing. And it gets worse, because CO not only prevents you from using the available oxygen and so causes suffocation, it is also a poison. So it is best you not only have plenty of ventilation, you must also make sure your heat source also burns cleanly. I have a CO alarm in my house for this very reason because I have a gas furnace.
Eric
