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Detail of the environmental conditioning duct, the cable tray, and some wiring bundles.

Picture 2 of 3.

The environmental conditioning duct distributed the temperature and pressure regulated, ground supplied, filtered air or gaseous nitrogen (GN₂) throughout the IU/S-IVB compartment through orifices in the duct. During the preflight phases of IU checkout, the purge system provided ventilating air. During fueling operations, it switched to GN₂, thus preventing the accumulation of dangerous or corrosive gases which might have affected operation or safety. Purging of the IU/S-IVB compartment terminated with umbilical separation.

The air entered the duct at the IU umbilical. The interior of the umbilical connection featured a Y splitter to route the incoming air in both directions from the umbilical panel.