I may be missing something, but how can a piece of plastic, whether made at home or from a supplier, stop a virus???? The link has a reusable respirator with one filter replaced, which raises all sorts of issues as to its efficacy. There is a company making an internal mic for the 3M half face systems which, if properly fit tested appears to work, but is anyone doing a formal fit test on these devices in both the static and dynamic mode?