As I aged, the cold began to get to me more and more. So about 6 seasons back I started using a small propane heater when hunting out of a box blind or pop-up ground blind when temps dropped into the 20's. I have not noticed any issues. Deer, (+coyotes, bobcats, and foxes) including .... mature does and bucks, have passed by withing 15-20 yards without indicating that they either heard or scented the heater. Mine is a very small version with only a "dome" type heater element.