Abstract: Apparatus to burn liquid fuels in a gaseous fuel burner, which includes preparatory apparatus for the atomization of liquid fuel oil preferably by steam, and the heating of the fuel droplets and steam so as to completely vaporize the liquid fuel. If atomization is by other means, steam is added prior to vaporization heating. The resulting oil vapor-steam mixture then goes to a burner which utilizes the central orifice of a conventional gas burner, plus an annular orifice concentric with the gas orifice, through which steam is supplied. Primary air is induced into the burner tube due to the high velocity jets of steam and of oil vapor-steam. The steam protects the hot vapor from the air until the combination issues from the end of the burner tube. For the use of gaseous fuel, the same burner is utilized except that the steam flow is turned off since the steam is not needed for the induction of the primary air, due to the higher velocity of the jets of gas.