348,767. Atmospheric gas burners. KEITH & BLACKMAN CO., Ltd., J., and KEITH, G., 27, Farringdon Avenue, London. March 13, 1930, No. 8126. [Classes 75 (i) and 75 (iii).] A gas heating system for bakers' ovens comprises burner devices, connections for supplying separately combustible and combustion-supporting media to the burner devices, means for governing the pressure of the combustible medium to atmospheric or sub-atmospheric pressure, induced draught means for withdrawing products of combustion and means for variably throttling the induced draught to regulate the flow of the media to the burner devices. Gas under the control of governors 12, Figs. 10 and 13, which may be of the kind described in Specification 270,786, [Class 75 (i), Burners &c.], is supplied to transverse combustion headers 5 arranged above and below the travelling chain or plate of the oven with atmospheric air and the combustion products pass from the combustion headers through groups of tubes 6 arranged longitudinally of the oven to transverse exhaust headers 7 leading into exhaust boxes 8 communicating through pipes 9, with an exhaust fan, the outlets from the headers being controlled by valves 15 which are provided with apertures 54 to prevent them being closed entirely. Air may also enter the exhaust boxes through the hollow spindles 151 of the valves. In place of exhaust fans ejectors may be employed as described in Specification 341,860, [Group XII]. Figs. 3 and 4 show the burners arranged in the combustion headers 5 which are provided with external ribs 5<2>. Gas under the control of an obturator 52 and cock 47 passes with a small quantity of air entering through ports 46 through a nipple 38 into a perforated tube 22 extending throughout the combustion header. Atmospheric air from a chamber 40 passes through a nipple 37 into a similar perforated tube 21. The air and rich aerated gas mixture passes through perforations 24, 25 and form intersecting streams which ignite and burn in the space provided. between tiles 27, 28 supported on transverse bars. 30 which with the tubes 21, 22 are resiliently supported on strips 33, 34. The tiles are held in place by wires 31. The gas cock handle 48 is interconnected with a plug valve 50 to control the admission of air from the atmosphere to the chamber 40. A sight hole 55, Fig. 8, and pilot light 56 are provided at the front of the combustion header, the pilot light being fed with gas drawn through an annular space 57 surrounding a tube 58 open to the atmosphere.