The present invention relates to a returnable dual duct type system for circulating cold and hot air, which comprises: a cold and hot air blower side dual pipe (20) inserted into and coupled to a blast pipe (10a) formed on one side of a cold and hot air blower (10) with a ventilator, and configured to form a dual pipe including an inner pipe (22) and an outer pipe (21)； a remote side dual pipe (30) disposed in a remote distance from the cold and hot air blower side dual pipe (20), and configured to form a dual pipe including an inner pipe (32) and an outer pipe (31) disposed outside the inner pipe (32)； an inner duct (51) connected between the inner pipe (22) of the cold and hot air blower side dual pipe (20) and the inner pipe (32) of the remote side dual pipe (30), and configured to form a first air blowing passage (L1) through which cold air or hot air, generated from the cold and hot air blower (10) and flowing through the blast pipe (10a) by the ventilator, flows； and an outer duct (52) connected between the outer pipe (21) of the cold and hot air blower side dual pipe (20) and the outer pipe (31) of the remote side dual pipe (30), and configured to form a second air blowing passage (L2), through which the cold or hot air flowing through the first air blowing passage (L1) is introduced and flows, wherein the remote side dual pipe (30) includes an air blowing direction reversing unit configured to reverse an air blowing direction of the cold or hot air flowing the first air blowing passage (L1), and the outer duct (52) includes a plurality of cold and hot air discharge holes (52a) to discharge the cold and hot air flowing through the second air blowing passage (L2). According to the present invention, it is possible to eliminate a temperature difference between a discharge hole of the cold and hot air blower and an end of an inner side of a facility.COPYRIGHT KIPO 2020본 발명은 송풍기를 구비하는 냉온풍기(10)의 일측에 구비된 송풍관(10a)에 끼워져 결합될 수 있고, 내부 관(22)과 외부 관(21)의 이중의 관을 형성하는 냉온풍기측
