Before revision: When used for cabin pressurization, the bleed air from the engine must first be cooled (as it exits the compressor stage at temperatures as high as 250 °C) by passing it through an air-to-air heat exchanger cooled by cold outside air.
After revision: When used for cabin pressurization, the bleed air from the engine must first be cooled (as it exits the compressor stage at temperatures as high as by passing it through an air-to-air heat exchanger cooled by cold outside air.