Circulation compound system comprising at least two associated heat exchangers, wherein at least one respective first heat exchanger (LWT2, LWT2-2) is arranged in a supply air volume flow and a respective second heat exchanger (LWT1, LWT2-1) is arranged in an exhaust air volume flow of an air treatment system, with a buffer reservoir (buffer, P2-1), which is connected to the circulation compound system, and with a heat pump, in which a heat carrier flows through an evaporator and a condenser, characterized, in that the buffer reservoir (buffer P2-1) is connected with the heat pump via a first pipe (L6-A) and a first three-way valve (V5, V2-5), and starting from the first three-way valve (V5, V2- 5) via a second pipe (L9; L2-7) and a lower twelfth pipe (PU, P2-U), and an eleventh pipe (L 11, L2-8) and an upper twelfth pipe (PO, P2-O), and that the buffer reservoir (buffer; P2-1) is connected via a second three-way valve (V6, V2-6) from the upper twelfth pipe (PO, P2-O) and the second pipe (L9; L2-7). and a third pipe (L10, L2-9) to the heat carrier circuit through the first (LWT2, LWT2-2) and second heat exchangers (LWT1, LWT2-1), and that the heat pump is integrated in the heat carrier circuit running through the circulation compound system, in which are included a first pipe (L6-A; L2K-A), the second pipe (L9; L2-7), the third pipe (L10; L2-9), a fourth pipe (L4; L2-3), a fifth pipe (L1-E; L2V-E), a sixth pipe (L1-A, L2V-A), an upper seventh pipe (L3-A, L2-1), a lower seventh pipe (L3-Z; L2-1), an eighth pipe (L6-E, L2K-E), a ninth pipe (L7, L2-6), a tenth pipe (L8; L2-5), the eleventh pipe (L11, L2-8), the upper twelfth pipe (PO, P2-O), the lower twelfth pipe (PU; P2-U), a first three-way valve (V5, V2-5), the second three-way valve (V6, V2-6), a third three-way Valve (V1, V2-1), a valve (V4, V2-4), the first heat exchanger (LWT2; LWT2-2) and the second heat exchanger (LWT1; LWT2-1), whereby optionally with the compressor switched off without the use of the heat pump, the heat carrier is conveyed by a pump, such as a feed pump of the heat pump, in the hydraulic circuit and is flowing through the pipes and valves of the system in the following order: via the first pipe (L6-A; L2K-A), the first three-way valve (V5, V2-5, V2-2), the second pipe (L9; L2-7), the second three-way valve (V6, V2-6), the third pipe (L10; L2-9), the first heat exchanger (LWT2; LWT2-2), the fourth pipe (L4; L2-3), the third three-way valve (V1; V2-1), via the fifth pipe (L1-E, L2V-E), the heat pump, the sixth pipe (L1-A, L2V-A), the second heat exchanger (LWT1, LWT2-1) via the upper seventh pipe (L3-A, L2-1), the lower seventh pipe (L3-Z, L2-1) and the eighth pipe (L6-E; L2K-E) back into the heat pump or when the compressor is switched on and with an empty buffer reservoir (P1-1) when switching on the heat pump in the heating case, the heat carrier which flows through the evaporator is flowing through the pipes and valves as follows: the sixth pipe (L1-A; L2V-A), the second heat exchanger (LWT1; LWT2-1), the seventh pipe (L3-A; L2-1), the ninth pipe (L7, L2-6), the third three-way valve (V1, V2-1) and the fifth pipe (L1-E, L2V-E) back into the heat pump, wherein further the heat carrier medium flows through the condenser of the heat pump then the first pipe (L6 -A; L2K-A), the first three-way valve (V5, V2-5, V2-2), the second pipe (L9, L2-7), the second three-way valve (V6, V2-6), the third pipe (L10 L2-9), the first heat exchanger (LWT2; LWT2-2), the fourth pipe (L4; L2-3), the tenth pipe (L8; L2-5), the valve (V4, V2-4),the lower seventh pipe (L3-Z; L2-1) and via the eighth pipe (L6-E; L2K-E) back into the heat pump. via the first pipe (L6-A; L2K-A), the first three-way valve (V5, V2-5, V2-2), the second pipe (L9; L2-7), the second three-way valve (V6, V2-6), the third pipe (L10; L2-9), the first heat exchanger (LWT2; LWT2-2), the fourth pipe (L4; L2-3), the third three-way valve (V1; V2-1), via the fifth pipe (L1-E, L2V-E), the heat pump, the sixth pipe (L1-A, L2V-A), the second heat exchanger (LWT1, LWT2-1) via the upper seventh pipe (L3-A, L2-1), the lower seventh pipe (L3-Z, L2-1) and the eighth pipe (L6-E; L2K-E) back into the heat pump or when the compressor is switched on and with an empty buffer reservoir (P1-1) when switching on the heat pump in the heating case, the heat carrier which flows through the evaporator is flowing through the pipes and valves as follows: the sixth pipe (L1-A; L2V-A), the second heat exchanger (LWT1; LWT2-1), the seventh pipe (L3-A; L2-1), the ninth pipe (L7, L2-6), the third three-way valve (V1, V2-1) and the fifth pipe (L1-E, L2V-E) back into the heat pump, wherein further the heat carrier medium flows through the condenser of the heat pump then the first pipe (L6 -A; L2K-A), the first three-way valve (V5, V2-5, V2-2), the second pipe (L9, L2-7), the second three-way valve (V6, V2-6), the third pipe (L10 L2-9), the first heat exchanger (LWT2; LWT2-2), the fourth pipe (L4; L2-3), the tenth pipe (L8; L2-5), the valve (V4, V2-4),the lower seventh pipe (L3-Z; L2-1) and via the eighth pipe (L6-E; L2K-E) back into the heat pump.