Hmm...that doesn't really answer the question and since so many high ranking purifiers (plus many industrial HEPA filters) use the same "squirrel cage fan to suck air through the filter" design, I don't believe it's true that there's a big advantage to blowing versus sucking.
I can believe that some home built box fan purifiers out perform some commercial units, but not as a blanket statement that a home made filter outperforms all commercial units.
> A self build system blows the air through a filter. Nearly all commercial systems suck the air trough a filter. Big difference.
But if you’re strapping a filter to a fan, it’s probably more efficient to blow through, since the air will be more focused (plus, it’s easier to mount due to front being flatter).
> I can believe that some home built box fan purifiers out perform some commercial units, but not as a blanket statement that a home made filter outperforms all commercial units.
Agreed. I recall seeing the stats they published and it looks like there are good purifiers among the more expensive ones (US$1000+), but apparently even in that price class they’re hit or miss and don’t always perform as well as a DIY solution could. Generally there’s a lot of information asymmetry, manufacturers want their margins so commercial air purifiers might often use something custom rather than a standard-compliant HEPA filter (either worse or slightly better but 10x more expensive than it should be) and make it difficult or impossible to swap it for something from a trusted third party. They’re counting on very small percentage of customers having properly calibrated particle counting equipment set up at home, they get away with providing misleading tech specs like CADR (or not providing them at all), and so on.
