When I was a kid in the '50's, probably 1/4 of the filling stations
heated the office with a wood stove running off waste oil. They would
put rocks in the stove, and drip oil from a copper tube on the rocks.
To light it off, they would use a wad of newspaper. There would be a
little black smoke coming from the chimney, not too bad. I don't
remember a significant smell of oil burning in the office. The rocks
would heat up and vaporize the oil to enable the combustion process.
Don't use limestone, use something more refractory, like the pumice
stone they sell at the plant places.

brownnsharp