To enable a burner to operate with LBTU (lean) gas, without losing the inherent advantage thereof by providing a second duct in parallel to an air duct and enabling a fuel to be introduced to an inner chamber of the burner.

A burner comprises, as its main components two hollow conical bodies 2 and 3 disposed in the direction of flow, the bodies of which are nested one inside the other. The longitudinal axes of symmetry of the partial bodies 2 and 3 are offset relative to each other. The adjacent walls of the partial bodies 2 and 3 form tangential air guide duct for combustion air 4 flowing into an inner chamber 5 of the burner 1 in the longitudinal direction thereof. Here, at least in cooperating with the tangentially extending air guide ducts, second ducts 6 and 7 are provided in parallel thereto, and fuel 8 can be introduced into the inner chamber 5 of the burner 1 through the ducts 6 and 7.