It is my (non-medical) understanding that air still flows through the masks. The best fabric for surgical face masks is cotton that can be easily washed and NON woven fabric as a filter that can be replaced several times during the day. You can purchase readymade carbon filters too.
452 activated carbon surgical mask products are offered for sale by suppliers on Alibaba.com, of which respirators & masks accounts for 54%, face shield accounts for 4%, and other security & protection products accounts for 1%.
50Pcs Disposable 3-Layer Masks, Anti Dust Breathable Disposable Earloop Mouth Face Mask, Comfortable Medical Sanitary Surgical （in Stock） 3.0 out of 5 stars 12 $20.39