Abstract: A flame retention head assembly for use in a fuel burner having a fuel nozzle mounted coaxially within an air pipe. This assembly comprises a continuously contoured, outwardly diverging flame retention head mounted concentrically within the air pipe in front of the fuel nozzle. This head successively defines, starting from its inlet end: an air-and-fuel mixture chamber; a first expansion chamber; a throttle and a second expansion chamber. A spinner plate is mounted transversely across the inlet end of the head. This plate comprises a central ring provided with a central hole having a diameter substantially identical to the one of the fuel nozzle, and a plurality of blades regularly distributed around the ring to cause air to enter and swirl into the mixture chamber. A round-shaped deflector is also mounted concentrically transversely within the retention head, to cause the air and fuel entering the head through its inlet end to stay longer within the first or second expansion chamber.