Abstract: A burner for gaseous fuels has a combustion zone of elongate cross section which is defined between divergent flame-confining walls. Each wall comprises a plurality of wall elements which are arranged edge to edge, the adjacent edges being relatively movable and mounted so as to prevent significant gas flow therebetween, the wall elements being rigidly secured to the remainder of the burner only at locations which are upstream of the combustion zone.

Abstract: An air-heating gas burner has a housing which includes a fuel gas supply passage and an air supply passage which open into a combustion zone defined between walls which extend downstream of outlets for the gas and air. Combustion products emerging from said combustion zone are confined between further walls which extend downstream to a location at which the combustion process is substantially complete. The burner is intended for mounting in an air conduit and the combustion products emerging from between the further walls have a particularly low content of oxides of nitrogen.