Abstract: A machine for flame processing textile fabric webs (27), especially a singeing machine, is equipped with a burner unit (35) which comprises a combustion chamber terminating in a singeing slit, connected to a gas mixing chamber by a mixture feed slot (7).To save energy, the width of the working flame should be adjustable continuously and with low operating cost, whereby in particular provision should be made for automatically adjusting the flame width to the width of the fabric web (27) being processed. For this purpose, the burner unit (35) is provided with one or two flexible sealing strips (13) for the mixture feed slot, said strips being insertable from one or both ends of the burner unit, each of said strips further having its outer end wound on a winding body (33), rotatable for adjusting the inner ends of sealing strips (13).