Comment by alpaca128

If you're into DIY it's possible to make a cheaper, more efficient and quieter air purifier than many consumer models. From what I understand the problem is that most devices on the market are designed to be small, which reduces the filter area and that again requires a stronger (louder & less efficient) fan. Going DIY also means no dependence on a specific brand's replacement filters.

Then again that doesn't mean off-the-shelf products are bad, for a single room even quite cheap ones can do the job. And they don't look like a fan taped onto filters, so there's that.