An environmental control system, characterized in that it comprises: a first air management subsystem having: a first heat exchanger assembly that includes a first main heat exchanger and a first secondary heat exchanger; wherein only one of the first main and first secondary heat exchangers (105a, 105b) have a catalytic coating; wherein the first main and the first secondary heat exchangers (105a, 105b) receive an ambient air; wherein the first main heat exchanger receives a first hot air; wherein the first secondary heat exchanger receives a second hot air; a first air cycle machine that produces the first hot air into the first main heat exchanger assembly and that produces a first conditioned air to a first enclosed environment, wherein the second hot air is produced by a source other than the first air cycle machine; a second air management subsystem having: a second heat exchanger assembly that includes a second main heat exchanger and a second secondary heat exchanger; wherein only one of the second main and second secondary heat exchangers have a catalytic coating; wherein the second main and the second secondary heat exchangers receive an ambient air; wherein the second main heat exchanger receives the first hot air; wherein the second secondary heat exchanger receives the first hot air; a second air cycle machine downstream of the second secondary heat exchanger and that produces a second conditioned air to the second main heat exchanger and further to a second enclosed environment. a first air management subsystem having: a first heat exchanger assembly that includes a first main heat exchanger and a first secondary heat exchanger; wherein only one of the first main and first secondary heat exchangers (105a, 105b) have a catalytic coating; wherein the first main and the first secondary heat exchangers (105a, 105b) receive an ambient air; wherein the first main heat exchanger receives a first hot air; wherein the first secondary heat exchanger receives a second hot air; a first air cycle machine that produces the first hot air into the first main heat exchanger assembly and that produces a first conditioned air to a first enclosed environment, wherein the second hot air is produced by a source other than the first air cycle machine; a first heat exchanger assembly that includes a first main heat exchanger and a first secondary heat exchanger; wherein only one of the first main and first secondary heat exchangers (105a, 105b) have a catalytic coating; wherein the first main and the first secondary heat exchangers (105a, 105b) receive an ambient air; wherein the first main heat exchanger receives a first hot air; wherein the first secondary heat exchanger receives a second hot air; a first air cycle machine that produces the first hot air into the first main heat exchanger assembly and that produces a first conditioned air to a first enclosed environment, wherein the second hot air is produced by a source other than the first air cycle machine; a second air management subsystem having: a second heat exchanger assembly that includes a second main heat exchanger and a second secondary heat exchanger; wherein only one of the second main and second secondary heat exchangers have a catalytic coating; wherein the second main and the second secondary heat exchangers receive an ambient air; wherein the second main heat exchanger receives the first hot air; wherein the second secondary heat exchanger receives the first hot air; a second air cycle machine downstream of the second secondary heat exchanger and that produces a second conditioned air to the second main heat exchanger and further to a second enclosed environment. a second heat exchanger assembly that includes a second main heat exchanger and a second secondary heat exchanger; wherein only one of the second main and second secondary heat exchangers have a catalytic coating; wherein the second main and the second secondary heat exchangers receive an ambient air; wherein the second main heat exchanger receives the first hot air; wherein the second secondary heat exchanger receives the first hot air; a second air cycle machine downstream of the second secondary heat exchanger and that produces a second conditioned air to the second main heat exchanger and further to a second enclosed environment.