This time I removed the tube from the back and placed my finger at the External Air Inlet connection. No doubt that the air goes IN as my finger was mildly sucked. Once the tube is connected to the dryer and the Inlet, the air is expelled from the open extremity of the hose.
So, I still don’t know exactly how it works, but I’m pleased with the little unit. Also, the suggestion to place a filter on the air pump was a great tip.