Incoming air from outside (or the airlock return air intake) comes through the pipe numbered "1". The blower housing and motor were attached to the fitting "2". A valve at "3" determined whether the air then went straight up to the heat exchanger via "4" or through the air filter "5". The valve at "6" was used to close off this whole side of the air system so that the filter could be swapped out without risk of air being sent on into the HDCP. The first air filter was set up similarly but with the added complexity of having the decontamination system in the loop.

Photo album created with Web Album Generator