I hunted at 9,000 feet the 1st week of October, the temperature was 18 degrees, I spent 2 nights in my blind with the wind blowing in excess of 40 miles and hour. I used the Mr. Heater in my brickhouse with the total scent control fabric which held the heat in when needed. With the thermometer reading 18 degrees when I woke up, within 10 minutes or so, my blind was 80 degrees inside. The heater heated things up and I was sweating, of course I had to turn it off and things cooled down pretty fast after that, But it sure was nice when I climbed out of my sleeping bag. I found a heater at cabelas that is much smaller and is around 800 btu's. That would be my choice as it has a 27 hour run time on one bottle of propane. I am fixing to spend 6 nights in the blind in a week or so, and I will sure have some heat in mine. The forcasters are predicting snow every night for the next 5 days or so. I love hunting migating mulies in the rut!!!!