An environmental control system of an aircraft comprising: a plurality of inlets (22, 24, 28) for receiving a plurality of mediums including a first medium, a second medium, and a third medium; an outlet for delivering a conditioned flow of the second medium to one or more loads of the aircraft; a ram air circuit including a ram air shell having at least one ram air heat exchanger (34, 36) positioned therein; at least one compressing device arranged in fluid communication with the ram air circuit and the outlet, the at least one compressing device including at least one compressor and at least one turbine operably coupled via a shaft; and an outflow heat exchanger arranged in fluid communication with the at least one compressing device, wherein within the outflow heat exchanger, the second medium output from the at least one compressing device is cooled by the third medium, wherein the second medium is fresh air; characterized in that: the at least one compressing device comprises a first compressing device and a second compressing device; wherein the first compressing device includes the at least one compressor as a first compressor and the at least one turbine and wherein the second compressing device includes a second compressor and a power turbine operably coupled via another shaft; the outflow heat exchanger is arranged directly downstream from an outlet of the first compressor relative to a flow of the second medium and upstream from the at least one ram air heat exchanger relative to a flow of the second medium, the second compressor being configured to receive the second medium from said outflow heat exchanger and to provide said second medium to the ram air heat exchanger; and the third medium output from the outflow heat exchanger is provided to the power turbine of the second compressing device. a plurality of inlets (22, 24, 28) for receiving a plurality of mediums including a first medium, a second medium, and a third medium; an outlet for delivering a conditioned flow of the second medium to one or more loads of the aircraft; a ram air circuit including a ram air shell having at least one ram air heat exchanger (34, 36) positioned therein; at least one compressing device arranged in fluid communication with the ram air circuit and the outlet, the at least one compressing device including at least one compressor and at least one turbine operably coupled via a shaft; and an outflow heat exchanger arranged in fluid communication with the at least one compressing device, wherein within the outflow heat exchanger, the second medium output from the at least one compressing device is cooled by the third medium, wherein the second medium is fresh air; characterized in that: the at least one compressing device comprises a first compressing device and a second compressing device; wherein the first compressing device includes the at least one compressor as a first compressor and the at least one turbine and wherein the second compressing device includes a second compressor and a power turbine operably coupled via another shaft; the outflow heat exchanger is arranged directly downstream from an outlet of the first compressor relative to a flow of the second medium and upstream from the at least one ram air heat exchanger relative to a flow of the second medium, the second compressor being configured to receive the second medium from said outflow heat exchanger and to provide said second medium to the ram air heat exchanger; and the third medium output from the outflow heat exchanger is provided to the power turbine of the second compressing device. the at least one compressing device comprises a first compressing device and a second compressing device; wherein the first compressing device includes the at least one compressor as a first compressor and the at least one turbine and wherein the second compressing device includes a second compressor and a power turbine operably coupled via another shaft; the outflow heat exchanger is arranged directly downstream from an outlet of the first compressor relative to a flow of the second medium and upstream from the at least one ram air heat exchanger relative to a flow of the second medium, the second compressor being configured to receive the second medium from said outflow heat exchanger and to provide said second medium to the ram air heat exchanger; and the third medium output from the outflow heat exchanger is provided to the power turbine of the second compressing device.