The example above shows a single heat exchanger unit. Mine has two heat exchangers in series for extra efficiency, over 90% heat transfer.
This unit is like opening a window for fresh air and keeping up to 90% of the heat or cooling that I have paid for. Indoor air quality is typically a lot worse than outdoor air quality. I don’t get a buildup of noxious fumes from building materials. The air has a fresher smell to it also.