I've used HEPA filters when I built an IV glove box a couple of years back. Don't recall the numbers, but I needed a fair bit of pressure from the air pump to get a decent flow rate. Somehow I don't think a fan will do it.
Did you even bother to look up basics of HEPA filters? They require an initial pressure drop of 300 Pa (https://en.wikipedia.org/wiki/HEPA#Specifications), which is beyond reach of any household fan. When the filter bcomes clogged, the pressure drop will increase even higher.