Report came out that two people died this weekend in there sleeper from Carbon Monoxide Poisoming. This should not have happened. Please go spend a few dollars on a DETECTOR!! All the money we spend to ice fish, Spend a few more. If not for you, for your family!!
Make sure you don't cover the intake manifold on your heater with snow either. My CO detector went off this weekend it was so cold that the air had little ice crystals and snow accumulated in the intake and eventually clogged it after 10 hours of run time. I was lucky.
I have a portable fish house I made out of canvas and thought the material would breath enough for a coleman stove. Boy was I wrong. 1 hour into fishing I had to go outside to answer to the call of nature. I got a terrible head ache when that rush of cold fresh air hit me. Gotta leave that zipper open a little.