By Jim Rosenthal Several months ago I wrote two articles for this site on the “Box Fan and MERV 13 Filter” air cleaner. They have been viewed over 30,000 times and many people have built these air cleaners following the simple directions in the articles. They are easy to construct, inexpensive and effective. In short, … Continue reading How to Improve the Efficiency of the Corsi-Rosenthal Box Air Cleaner