This is a DIY project. The project theme is something is better than nothing. For someone who don't have N95 mask. Remember before making it: this design not approved by physician or any health organization. So do it at your own risk. After making it should perform working test of the mask. Should perform N95 testing procedure with this. You can find the N95 mask testing procedure in the google.
You can use it multiple time. After replacing new filter. Should perform disinfection procedure of the mask before putting new filter.
Keep research to make it more secure and protective. And you have to study abot the filter febrics and filter foam to use in the mask.
I put only $5 of cost instead of giving free, due to some reasons.
Note: Should add filler and apply paint to all 3d printed parts, because 3d printed parts are not 100% air sealed. It may have some micro hole, due to printing error.