I spend an awful lot of time in my basement darkroom and it takes a tremendous amount of electric space heater use to get the temp up to 60F. Or I could run the gas furnace and heat the whole unoccupied house at an astronomical cost. This morning as I went to work the temp down there was 52 degrees F. Long johns, fingerless gloves, tuke and jacket. But a friend dropped by with a propane heater he isn't using and the thing is fantastic. A heating element about the size of a tea saucer and it cranks out the heat like you wouldn't believe and it burns at a color that looks about like my safe light. I am in heat heaven and may not come out of the darkroom till Spring. I will see how much it costs to get new cans of gas but my friend assures me it will be less than 20 bucks a month.
Yes I have good ventilation.