A conveyor oven comprising: an oven chamber that comprises an inlet and an outlet; a conveyor disposed to transport food through said oven chamber; at least one blower (42, 44) disposed to provide at least a first air stream to said oven chamber that traverses said oven chamber in a first path toward one of said inlet and outlet; a heating chamber disposed adjacent said oven chamber; and a ductwork in fluid communication with said at least one blower (42,44); wherein said ductwork comprises: a plurality of upper and lower impingement plenums (28, 32, 30, 34) disposed on either side of said conveyor to provide said first air stream toward said conveyor as columns of impingement air that turn into said first path along said conveyor, and characterised in that the conveyor oven further comprises: a first plenum and a second plenum in fluid communication with one of said plurality of lower impingement plenums (32, 34) to provide, with the at least one blower (42, 44), a second air stream that redirects said first path of said first air stream to an air return plenum (58, 60) so as to substantially prevent said first air stream from escaping to ambient via said at least one of said inlet and outlet. an oven chamber that comprises an inlet and an outlet; a conveyor disposed to transport food through said oven chamber; at least one blower (42, 44) disposed to provide at least a first air stream to said oven chamber that traverses said oven chamber in a first path toward one of said inlet and outlet; a heating chamber disposed adjacent said oven chamber; and a ductwork in fluid communication with said at least one blower (42,44); wherein said ductwork comprises: a plurality of upper and lower impingement plenums (28, 32, 30, 34) disposed on either side of said conveyor to provide said first air stream toward said conveyor as columns of impingement air that turn into said first path along said conveyor, and characterised in that the conveyor oven further comprises: a first plenum and a second plenum in fluid communication with one of said plurality of lower impingement plenums (32, 34) to provide, with the at least one blower (42, 44), a second air stream that redirects said first path of said first air stream to an air return plenum (58, 60) so as to substantially prevent said first air stream from escaping to ambient via said at least one of said inlet and outlet. a plurality of upper and lower impingement plenums (28, 32, 30, 34) disposed on either side of said conveyor to provide said first air stream toward said conveyor as columns of impingement air that turn into said first path along said conveyor, and characterised in that the conveyor oven further comprises: a first plenum and a second plenum in fluid communication with one of said plurality of lower impingement plenums (32, 34) to provide, with the at least one blower (42, 44), a second air stream that redirects said first path of said first air stream to an air return plenum (58, 60) so as to substantially prevent said first air stream from escaping to ambient via said at least one of said inlet and outlet. a first plenum and a second plenum in fluid communication with one of said plurality of lower impingement plenums (32, 34) to provide, with the at least one blower (42, 44), a second air stream that redirects said first path of said first air stream to an air return plenum (58, 60) so as to substantially prevent said first air stream from escaping to ambient via said at least one of said inlet and outlet.