I used one for many years. I have carbon monoxide detectors in the garage/shop that would kick on, if I didn't have the garage door cracked open about 2 inches. I later added two 1500 W toaster Electric heaters and then added a 5000 W shop heater. I didn't like the moisture accumulating on the garage door and metal machines from the propane salamander. I only used the salamander for initial boost, then turned it off, shut the garage doors and went to electric. December January and February usually ran me two x 20 lb. lp + 100–$200 in Electric heat.
Subsequently, I finally added a 30,000 BTU overhead radiant NG heater. Since, the salamander, the two toasters and salamander have been removed and sold. Since going NG, my operating costs have dropped to about $80 a month on average which is about 50% of the operating cost prior.
I never keep my garage/shop below 62°F, but when I'm in there, the thermostat is always set to 68°F or higher. I never park cars in my shop.
I consider this a learning the hard way, Or a step-by-step investment that I wish I didn't take. But it was what was affordable to me at the time.