The Corsi-Rosenthal design is legit--it uses paper filters which are quiet effective at removing pollutants from the air in a few air changes. It's the filter-

The Corsi-Rosenthal design is legit--it uses paper filters which are quiet effective at removing pollutants from the air in a few air changes. It's the filter-less / ion / electrostatic air cleaners that have quite questionable or non-existent air filtering qualities.