A flare stack gas burner for waste combustible gas from oil refineries, chemical plants, oil production rigs, LPG and other marketing terminals, pipe lines and the like is disclosed which includes a stack for waste gas delivery with an air delivery pipe therein with a plurality of outwardly extending hollow vanes at the top with fixed inclined nozzles along the tops of the vanes for discharge of air into the combustible gas advancing in the stack in a plurality of flat inclined streams at an inclination from the horizontal in a hollow frustoconical vortex combustion path, the inclined streams contacting combustible gas on each face and into the vortex path and around the exterior for completing combustion. The burner head has an enclosing shroud at the top to which steam is delivered at the bottom of the shroud for inducing combustion supporting air, the air being delivered in a hollow cylindrical stream surrounding the vortex path, with additional steam being introduced into and through the cylindrical stream, the air inlet path to the cylindrical stream being shielded to reduce noise emission.