An airplane, comprising: a chamber; an engine comprising a high pressure port and a low pressure port; an environmental control system (700, 800) in fluid communication with the chamber comprising: an inlet configured to receive a first medium; a secondary heat exchanger; a compressing device comprising a compressor, a first turbine, a second turbine, a fan and a shaft; a high pressure water separator comprising a condenser; wherein the environmental control system is operable in a plurality of modes including a low-pressure mode and a boost cooling mode; wherein, in the low-pressure mode, the secondary heat exchanger is configured to receive a first portion of the first medium from the inlet, where it is cooled to a temperature requested by the chamber and output to the chamber via a second valve (V5.2); wherein, in said low-pressure mode, the second turbine is configured to receive a second portion of the first medium from the inlet via a third valve (V5.3), wherein the second turbine is configured to expand and extract work from the second portion of the first medium, which is used to keep the compressing device turning at a minimum speed; wherein, in the boost cooling mode, the compressor is configured to receive a first portion of the first medium from the inlet via a first valve (V5.1) and heat, pressurize and subsequently output the first portion of the first medium to the secondary heat exchanger, the secondary heat exchanger is configured to cool and subsequently output the first portion of the first medium to the high pressure water separator, the high pressure water separator is configured to cool, dry and subsequently output the first portion of the first medium to the first turbine, the first turbine is configured to expand and extract work from the first portion of the first medium to drive the compressor and the fan, the fan being configured to pull ram air through the secondary heat exchanger, the first turbine is configured to output the first portion of the first medium, where it is mixed with recirculation air from the chamber, cools air in the condenser and sent to condition the chamber; wherein, in said boost cooling mode, the second turbine is configured to receive a second portion of the first medium from the inlet via the third valve (V5.3) and expand and extract work from the second portion of the first medium to provide additional energy to the compressing device, which also acts to drive the first medium through the first turbine; wherein, in both the low-pressure mode and the boost cooling mode, the inlet coincides with the low pressure port. a chamber; an engine comprising a high pressure port and a low pressure port; an inlet configured to receive a first medium; a secondary heat exchanger; a compressing device comprising a compressor, a first turbine, a second turbine, a fan and a shaft; a high pressure water separator comprising a condenser; wherein the environmental control system is operable in a plurality of modes including a low-pressure mode and a boost cooling mode; wherein, in the low-pressure mode, the secondary heat exchanger is configured to receive a first portion of the first medium from the inlet, where it is cooled to a temperature requested by the chamber and output to the chamber via a second valve (V5.2); wherein, in said low-pressure mode, the second turbine is configured to receive a second portion of the first medium from the inlet via a third valve (V5.3), wherein the second turbine is configured to expand and extract work from the second portion of the first medium, which is used to keep the compressing device turning at a minimum speed; wherein, in the boost cooling mode, the compressor is configured to receive a first portion of the first medium from the inlet via a first valve (V5.1) and heat, pressurize and subsequently output the first portion of the first medium to the secondary heat exchanger, the secondary heat exchanger is configured to cool and subsequently output the first portion of the first medium to the high pressure water separator, the high pressure water separator is configured to cool, dry and subsequently output the first portion of the first medium to the first turbine, the first turbine is configured to expand and extract work from the first portion of the first medium to drive the compressor and the fan, the fan being configured to pull ram air through the secondary heat exchanger, the first turbine is configured to output the first portion of the first medium, where it is mixed with recirculation air from the chamber, cools air in the condenser and sent to condition the chamber; wherein, in said boost cooling mode, the second turbine is configured to receive a second portion of the first medium from the inlet via the third valve (V5.3) and expand and extract work from the second portion of the first medium to provide additional energy to the compressing device, which also acts to drive the first medium through the first turbine; wherein, in both the low-pressure mode and the boost cooling mode, the inlet coincides with the low pressure port.