HEPA (High-efficiency particulate air) filters remove at least 99.97% of airborne articles 0.3 micrometers (µm) in diameter or larger.
I started with figuring out how to adapt the rectangle filter to the round exhaust port. I had a 2.5" to 4" adaptor that would be a good start but the exhaust port was only 2" in diameter. So I cut it in half and removed the excess material to form a 2" pipe and plastic welded it back together.
I had to be careful to not get glue on the pipe, as that hole would serve as the maintenance port for cleaning.
Wham bam thankyou mam, shop vac now has a HEPA filter.
Till next time.