When you think about it, I don`t think masks have ever been designed explicitly to keep stuff in. As far as I know masks have traditionally been designed to keep stuff out. Keeping stuff in is a new concept.
Harry On Sun, Aug 9, 2020 at 5:29 PM Jed Rothwell <jedrothw...@gmail.com> wrote: > This is off-topic, but important. > > It turns out that cheap, throw-away "surgical mask, 3-layer" type masks > work best. These are the ones you can buy anywhere nowadays. Office Depot > sells them cheap. > > See this research article in Science: > > https://advances.sciencemag.org/content/early/2020/08/07/sciadv.abd3083 > > Knitted and bandana types are not recommended. > >> >