An easy way to make a polypropylene filter is to cut out a square to fit your mask from a reusable fabric shopping bag with the No. 5 recyclable label. These are also the kind of tote bags ...

And now that polypropylene is recommended in masks, should I be worried about breathing it in? Here are the answers to your latest questions on masks and COVID-19. How close can you get to others ...

According to a report in the Huffington Post, filter materials like HEPA and polypropylene should be placed between two layers of fabric like cotton, silk or nylon when the masks are being produced.