>The 20" box fan + MERV furnace filter hack

Living here in the west with hyper toxic AQI for the better part of two months now, I decided that the low CFM and leakage of a DIY box fan are not adequate to keep up. I went with a far more industrial solution: I went to an indoor grow shop and bought an activated carbon filter and high CFM inline fan. Cost $150 and is a bit noisy, but has been well worth it.