Have a look on Facebook for the page run by Prof. K Kwong. He's a former Chemistry teacher at HK Polytechnic and has done loads of testing and design for re-usable cotton masks and gives some good guides on how they can be supplemented by tissues or kitchen towels to give up to N95 quality. Another Facebook page is HKMasks that take the Professor's work and show how to make your own (I just bought mine from G.O.D. for $70) Unless you're in an operating theatre, you really don't need N95 but the choice is yours.
