I've had my heater in my shelter tub without problems. Just turn it off when you leave and give it time to cool off before you fold it up. Its more likely to burn the canvas that the tub. If you use a sunflower type I think they are hotter and more likely to burn something. I keep mine on low most of the time but even with it on high when its really cold no part of the tub gets that hot as to melt it. Don't let your fishing line get to close though, heat does line no favors..