After watching this segment, I immediately bought a 20" box fan, a 20x20 MERV 11 filter, and put one together. It kicks the pants off of air purifiers twice the price and it moves a lot of air through. Best investment ever. CBC was testing CADR, which is one metric among others, but an important one if you're looking to clean a room's air, fast.
I have an Awair and did that dance of turning on the box fan filter when levels were higher than normal, then turning it back off once in normal range.
Now I much prefer keeping a quieter (less performant unit) on continuously to keep the levels low.