Finally, at the highest tier of protection, you can buy powered air purifying respirators for $300 or make your own for $15-30. I don’t have any experience with either option, so I can’t comment much.
The usual problem with (all?, most? of) the personal-use, non-professional PAPRs, including the $300 example you mentioned, is that they haven’t been independently tested by anyone.
With the DIY PAPRs you mentioned, you at least know that the filters should work (since they’re certified for hospital use) and when you build it, it’s easier to ensure that the seals also work.
The usual problem with (all?, most? of) the personal-use, non-professional PAPRs, including the $300 example you mentioned, is that they haven’t been independently tested by anyone.
With the DIY PAPRs you mentioned, you at least know that the filters should work (since they’re certified for hospital use) and when you build it, it’s easier to ensure that the seals also work.