This pattern has the chin piece and has been tested. Here are the filtering results
When we made the masks out of the following materials they filtered out 87% of particles based on the Portacount fit test:
+ One layer of oil absorbent towel + one layer of shop towel (Zep, Wypall or Toolbox brands)
+ Two layers of shop towel (Zep, Wypall, or Toolbox brands
When we made the mask out of t ight woven cotton and added the o ptional pocket piece, filling it with any of the following filters, the mask filtered out 82% of particles based on the Portacount fit test:
-W ypall X80 Towel
-Z epShopTowel
-T oolboxShopTowel
When we made the mask out of t ight woven cotton and added the o ptional pocket piece, filling it with the following filter, the mask filtered out 70% of particles based on the Portacount fit test: -S cottShopTowel
When we made the mask out of t ight woven cotton and added the o ptional insert piece and filleditwithn ofilters,themaskfilteredout52%ofparticlesbasedonthePortacountfittest.
https://cdn.shopify.com/s/files/1/0050/2474/3524/files/Suay_Mask_Pattern_1.1.pdf?v=1586398631
I got the link from this article.
Here are the instructions for a better-fitting homemade mask that can filter particles 2x better than cotton, created by three clothing designers