A conveyor-type oven comprising: a housing (12, 112, 212) defining a baking chamber (26, 126, 226), and a primary chamber (28, 128, 228) that is positioned beneath the baking chamber, the housing having an opening (22, 122, 222, 24, 124, 224) at each of the two longitudinal ends of the baking chamber; a gas burner (30, 130, 230) or a resistive-type heating element underneath the baking chamber that is arranged to introduce hot air into the primary chamber; a continuous conveyor belt (32, 132, 232) for transporting food to be cooked through the baking chamber; an upper plenum assembly comprising a box (44, 144, 244) that is supported by the housing (12, 112, 212) across the top of the baking chamber (26, 126, 226) and includes a plurality of orifices from which to discharge hot air downwardly towards the conveyor belt; a lower plenum assembly comprising first and second boxes (38, 138, 238), each box being disposed in the baking chamber (26, 126, 226) and the upper side of each box (38, 138, 238) having a plurality of orifices from which to discharge hot air upwardly towards the conveyor belt; ducting (40, 140, 240, 42, 142, 242, 46, 146, 246) that interconnects the primary chamber (28, 128, 228) with the upper and lower plenum assemblies; and fans (36, 136, 236) that are operable to transport hot air from the primary chamber (28, 128, 228) through the ducting to the upper and lower plenum assemblies; each of said fans (36, 136, 236) being underneath the baking chamber (26, 126, 226); the ducting including two upper ducts (46, 146, 246) that each extends upwardly on opposing sides of the baking chamber (26, 126, 226) and opens into the box (44, 144, 244) of the upper plenum assembly for movement of hot air to the box (44, 144, 244) in use of the oven; characterised in that said ducting includes a manifold portion (40, 140, 240) that receives hot air from the fans (36, 136, 236) in use of the oven, and first and second lower ducts (42, 142, 242) that each interconnect the manifold portion (40, 140, 240) with the respective first and second boxes (38, 138, 238) of the lower plenum assembly, the lower ducts (42, 142, 242) and manifold portion 40 being located underneath the baking chamber, such that, in use of the oven, hot air from the fans (36, 136, 236) moves linearly upwards in the direction of its natural buoyancy into the baking chamber. a housing (12, 112, 212) defining a baking chamber (26, 126, 226), and a primary chamber (28, 128, 228) that is positioned beneath the baking chamber, the housing having an opening (22, 122, 222, 24, 124, 224) at each of the two longitudinal ends of the baking chamber; a gas burner (30, 130, 230) or a resistive-type heating element underneath the baking chamber that is arranged to introduce hot air into the primary chamber; a continuous conveyor belt (32, 132, 232) for transporting food to be cooked through the baking chamber; an upper plenum assembly comprising a box (44, 144, 244) that is supported by the housing (12, 112, 212) across the top of the baking chamber (26, 126, 226) and includes a plurality of orifices from which to discharge hot air downwardly towards the conveyor belt; a lower plenum assembly comprising first and second boxes (38, 138, 238), each box being disposed in the baking chamber (26, 126, 226) and the upper side of each box (38, 138, 238) having a plurality of orifices from which to discharge hot air upwardly towards the conveyor belt; ducting (40, 140, 240, 42, 142, 242, 46, 146, 246) that interconnects the primary chamber (28, 128, 228) with the upper and lower plenum assemblies; and fans (36, 136, 236) that are operable to transport hot air from the primary chamber (28, 128, 228) through the ducting to the upper and lower plenum assemblies; each of said fans (36, 136, 236) being underneath the baking chamber (26, 126, 226); the ducting including two upper ducts (46, 146, 246) that each extends upwardly on opposing sides of the baking chamber (26, 126, 226) and opens into the box (44, 144, 244) of the upper plenum assembly for movement of hot air to the box (44, 144, 244) in use of the oven; characterised in that said ducting includes a manifold portion (40, 140, 240) that receives hot air from the fans (36, 136, 236) in use of the oven, and first and second lower ducts (42, 142, 242) that each interconnect the manifold portion (40, 140, 240) with the respective first and second boxes (38, 138, 238) of the lower plenum assembly, the lower ducts (42, 142, 242) and manifold portion 40 being located underneath the baking chamber, such that, in use of the oven, hot air from the fans (36, 136, 236) moves linearly upwards in the direction of its natural buoyancy into the baking chamber.