Building a 12x20 insulated room in my pole barn as my new fur shed / workshop. I plan to run a small electric "milk house" heater on a thermostat to keep it around 40* when I'm not in there if temps drop below freezing. I plan to use either a small propane salamander (30,000 btu )to heat up the room quick for working or a slower kero wick heater to keep it more even steady heat. I know both produce about a gallon of water per gallon of fuel, but will using either for short periods be a issue for rusting tools and drying fur ? Will a dehumidifier offset the moisture ? What would be the max humidity level for a room that fur can be safely dried without molding ? -Thanks

I run a small propane heater in my fur shed and moisture has never been a problem. The air in winter is so dry I don't think adding moisture makes a difference. I know my furs dry faster with gas heat than when the temp remains below freezing in there.

Have you considered electric, baseboard heat? I have a 6' baseboard heater in my insulated 12X16 and it is plenty of heat and easy to regulate with a thermostat. No moisture or carbon monoxide to worry about either.

I had moisture problem with propane in garage

When I lived in western Ky I used propane and kerosene to heat my garage and it was a problem drying furs at times. Windows fogged, lots of moisture inside, etc. It depended a lot on the weather - when it was rainy it was a problem, clear and dry outside and it was OK. Whether propane or kerosene will work for you depends a lot on the weather where you live.

I think the best option is a wood stove or propane heater that vents outside. That way you are always pulling inside air from the garage for combustion and venting it out. That air is then replaced with dryer air from outside. However, a wood stove in a garage with vehicles, gas, etc, is not a great idea. An overhead mount propane heater vented outside would work well.

Could you explain ?

Do those "vent free" wall mounted type propane heaters put moisture in the air and or deplete oxygen ?

I use ventless heaters in my house all I run 90% of the winter completely safe and no moister that I know off I dry taxidermy and furs in my kitchen about 15 to 20 from one never have eny trouble!
Colt

I use a ventless propane fireplace as a supplemental heat source in the winter. My house is still dry enough to give you a static shock when walking across carpet in socks!

I had vent free propane heater in my garage and had ice on in side of window, an water running down window when it warm up ,water dripping from ceiling it was bad. building was to tight drywall

now I'm in colder area than these other guy maybe that makes a different

I heat with propane in my fur shed. I do run a dehumidifier. Propane heat, drying fur and wet animals put out a lot of moisture.

Ran a vent free and fans going for the circulation of the room at all times, never had a issue might have to do with many things like humidity and insulation value for the temperature swings.

Here is the problem.

The equation for combustion of propane is: C3H8 + 5O2 yields 3CO2 + 4H2O + heat

For kerosene: 2C12H26 + 37O2 yields 24CO2 + 26H2O + heat

Burning kerosene or propane yields H20 (water) as one of the byproducts. If you vent it into your fur shed it will increase the humidity. Your furs are also adding moisture to the air as they dry. Whether it is a problem depends on the weather conditions where you live and maybe on the weather on any particular day.

yes any fossil fuel heat source without a exhaust add moisture in the form of carbon monoxide