I got a CR subscription to look at air filters. For good air filtering you really only need a hepa filter ($20) in front of a fan ($20), but CR only analyses the performance of brand name products ($200).
HEPA filtration only matters if you have a clean side and a dirty side. Most air filters exhaust clean air into the same room as the intake, so all that matters is clean air delivery rate [0]. It's often possible to get better clean air delivery rate using higher flow through a less restrictive non-HEPA filter.
The removal efficiency of the filter is built in to CADR, so say a MERV-14 filter with higher air flow and a HEPA filter with lower air flow can have the same CADR.
Not exactly. To be comparable to the good air filter products, you'd want to build a cube of air filters and attach the fan so it pulls air through the cube. Fun DIY project, but it's not for everyone. There's a good YouTube video for it.
