Hoping you really have hay fewer and no evil virus!!! I also pondered to sew such a mask, because I am allergic to the standard masks. I had to wear them constantly last year when I visited my father in hospital, and over time i developed an intense allergy. But I am still unsure how good the protection of these handmade masks is...
The mask that I made is primarily for pollen outside. It is not a substitute for a hospital mask or a surgical mask which has a specific porosity. You may be able to use a cloth mask with a standard coffee filter inside. The surgical masks have 3 layers. If I used my mask with the general public around, then I definitely would add another layer. Good luck.