I left mine run on low over night that weekend it was -60 out with windchill durning the ice fishing tournament. Never missed a beat showed up to a warm shack. It ran on high all day and we fished in the hub in a hoodie. The 20 pound tank was outside the whole time.
I had to throw a big buddy out also from my flip over. A seal blew out inside the top of the unit. It was about 3 or 4 years old. Called Mr Heater about it. They asked me a few questions. They sent me out a new heater, hose and filter. Had it in 2 days. They paid to ship the old one back to investigate what happened. Then sent me an email with the results. Very happy with the customer service