Abstract: A burner for gaseous fuel having an air supply chamber maintained at a predetermined uniform pressure and ports leading to at least three separate chambers in a burner assembly. The first of these ports receives a mixture of fuel and air from the supply chamber and directs the same through a first chamber to burner ports in the assembly. The other two chambers receive secondary air from the air supply chamber and direct it to positions closely adjacent opposite sides of the burner ports. The burner ports are arranged in rows and the first chamber is of tapered section along the rows of burner ports.