air from the atmosphere each of the defined inshot burners includes a hollow body which is substantially in the shape of an elongated and truncated cone i e in a frusto conical shape the base of the frusto conical shape is disposed at the flame exit end of the hollow body and the apex end of elongated truncated cone is disposed at the gaseous fuel and air entry end thereof the flared end of the hollow burner body is connected to the apex end of the frusto conical body a gas manifold having a plurality of gaseous conduits connected thereto for supplying the gaseous fuel to each of the inshot burners is provided bracket means are also necessarily provided for mounting the upper and the lower burner half shells in mutually operative disposition with respect to the induced draft combustion heat exchanger a plurality of longitudinally extending connection apertures are disposed in spaced array in each of the upper and lower burner half shells when the burner half shells are disposed in registered alignment these connection apertures are disposed and in mutually congruent spaced array in each of the upper and lower burner half shells one of the upper and lower burner half shells includes a corresponding disposed flange means for bending over at the corresponding connection aperture for mechanically securing the upper and lower burner half shells together these connection apertures preferably alternate on the selected burner half shell with the longitudinally extending burner halves although other arrangements are contemplated each inshot burner further includes a corresponding.