Abstract: In a fluent fuel burner using a flame anchor plate, secondary air from a plenum leaves the plenum through a restricted passage so that the secondary air is at high velocity and correspondingly low pressure and this low pressure is used to suck the flame to the rim of the anchor plate. Two dual fuel burners are described in which a gaseous fuel introduction means has an enlarged end portion which extends from within the air plenum into a combustion space, the said portion having slots in it to allow primary air to enter the said portion to serve as primary air for combustion, and which has associated with it a flame anchor plate. The plenum has a wall on the combustion side with a hole in it. In one embodiment, the anchor plate overlies the rim of the hole so that a narrow annular passage defined between the plate and the wall directs the secondary air in a radial blast.