biggoolies
Adventurer
CO is not the concern with a catalytic heater, it is oxygen consumption. That is why you have to have the window open when you use one so you can replenish the oxygen in the room. The window slightly open is enough to replenish the oxygen. If you are concerned even with the window open, you can purchase an oxygen analyzer which generally are used in the medical industry but can be used in this situation. Oxygen normally is 21%. You can set the alarm on these to say 19%. Best thing to do though is to have a warm sleeping bag warm socks and a beanie. Use the heater before you go to bed and when you wake up in the morning. A toque warm socks and a warm bag go a long way. That is what I did overnight on the ski hill.