We ice fished to Mosquito Lake today. Got to our spot, set the shed up, drilled our holes and I fired the heater up. It ran for about 45 minutes then shut off and wouldn't light again. I knew it wasn't out of gas because I just put a new tank on today but I still changed the tank. It still didn't light so I just fired the lantern up and used that for heat. I tried the heater a couple hours later and it started and ran for about 30 minutes then went out again and wouldn't light again so I lite the lantern again and used it until we were ready to leave. When I got home I took the heater to the basement and fired it up. It ran for 2 hours with no problems so I shut it off. I know it has a low oxygen shutoff and now I'm thinking that's why it shutoff in the shed. We had the shed zipped up tight because it was snowing. Just wondered if anyone else ever had this problem.