So I did this with a cheap $15 box fan and a MERV 13 filter. It performs very poorly, the filter impedes the airflow too much and the fan actually will intake m

So I did this with a cheap $15 box fan and a MERV 13 filter. It performs very poorly, the filter impedes the airflow too much and the fan actually will intake most of the airflow from the front corners of the output side because it's less resistance. Axial flow fans only operate efficiently at low static pressures. This is why your home forced air system uses a centrifugal blower, which is more efficient at high static pressures. tl;dr I'd use a MERV 11 or less on a cheap box fan. You aren't going to make a Class 100 clean room out of your house with this kind of setup.