1,210,369. Glass annealing lehrs. E. W. BOWMAN. 18 July, 1969 [22 April, 1969], No. 36386/69. Heading F4B. In a glass annealing lehr comprising a tunnel-shaped chamber 1 having therein an endless conveyer 2 passing through preheating firing and cooling zones, the firing zones 2-5 (see Fig. 3) comprise an annealing chamber and heating chamber 26 above and below the conveyer 2 respectively, burner ports 27 spaced along the side wall of the lehr provided with burners 28, the ports on opposite side walls being staggered with brick piers 29 being provided between the burner ports 27 to prevent stratification of the hot gases longitudinally of the lehr, the hot gases from said burners being forced by a circulation fan 33 through chamber 1 and back into the chamber 26 via return ducts 30, pairs of dampers 40 for controlling the inlet of atmospheric air into a duct above the fan 33, and an exhaust flue 41 having a damper 42 by means of which the pressure in the chamber 1 can be regulated. Each zone is defined by vertically adjustable partitions 43 and by partition walls as shown at 44 and 45, the hot gases circulating in a zone being thus prevented from passing outside the zone into adjacent zones.