CBC Marketplace had an interesting segment this week, on home air filters.
https://www.cbc.ca/news/business/portable-air-purifier-tests-marketplace-1.5900782

Interesting as well because we had built a DIY air filter a month or two ago:


Unlike the one featured on Marketplace, ours featured two filters to provide for more airflow, lessening the load on the fan motor.

In any event, their testing showed the most expensive Dyson (at $800), was one of the worst performing. The smallest unit was the worst performing on the CADR scale, a combination of how well it filters and how much air it moves.

Our DIY unit came in the middle of the pack but at the absolute lowest price. It’s airflow is pretty high, so I suspect it lags a little in the filtration arena.

Ours used an existing box fan and the purchase of two furnace filters from Home Depot for approx $20 each.
Our history with air cleaners in the past was that when it came time to purchase a new filter, they had gone out of production and you could not get them at all. Meaning the entire $100+ air cleaner was useless. Hence the DIY design. furnace filters will never go out of production.