Abstract: An improved two-stage combustion chamber for burning waste hydrocarbons such as crank case oil, spent motor oil, transmission fluid, lubrication dopes, and heavy bodied gear lubes. The combustion chamber is formed from a plurality of spaced apart, stacked annular rings that form a flame containment housing having superheated surfaces. The flame containment housing contains the flame of an atomizing oil burner suitable for burning the variable viscosity waste hydrocarbons. The annular rings include outer walls and inwardly extending flanges that intercept unburned fuel droplets and combustion byproducts, vaporizing the droplets and/or stimulating secondary combustion. The annular rings are removable and replaceable, and are supported in spaced-apart relation by spacers on a plurality of support rods.