The propane heaters are capable of putting SO much moisture into the air that it can get silly. (rust issues on your bare steel!) Around here, I am told that drywallers cannot use them as the "mud" will never dry and I have also been told (by a buddy who is a drywaller) that in some cases the mud just runs down the wall overnight. They use either massive (and expen$ive to run) electric ones or else the kerosene ones.
And yes, I use a kero-powered one. They do smell up the place (a lot), but running a 220 volt electric one just gets too $pendy for my budget. As soon as I can get the rest of the insulation done in my shop I'll be firing up the nat gas-powered boiler (again) to run the radiant floor heat