Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4293629.
This is a Remix of the famous COVID-19 MASK v2. https://www.thingiverse.com/thing:4225667 This "simple cap" replaces the "connector" and "cap" of the original design. It can be inserted from the outside or inside (I recommend from the outside). The filter material needs to be bigger than the cap, at least 50 x 50 mm (> 0.3 mm thick) . The filter itself seals the cap. I used a anti-allergen vacuum bag as filter. The denser layer should face the wearer. Also the edges shouldn't be exposed to the wearer, because some manufacturers use antimicrobial powders between the layers, which can do warm. * I mostly recommend ' Sterilization Wrap ', it can supposedly filter down to 0.3 micron (1 micron of vakuum bags), but can be hard to get by non-professionals.
In the pictures you see me using " Car Door Edge Guard " for better sealing against the face.
*statements of manufacturers: Philips: "...have no informations, if materials do warm..." Militta (swirl): "...don't recommend vacuum cleaner bags for mask making" Numatic (henry): "...unable to substantiate their effectiveness when used for this purpose..."
All didn't mentioned antimicrobial powders. But could confirm the filtration of 0.3 micron, which is smaller than the particles used for testing N95 or N99 masks (FFP2 FFP3). Particles smaller 0.6 micron are not considered infectious.
Sources:
Studie for alternative materials: https://www.cambridge.org/core/journals/disaster-medicine-and-public-health-preparedness/article/testing-the-efficacy-of-homemade-masks-would-they-protect-in-an-influenza-pandemic/0921A05A69A9419C862FA2F35F819D55
Blog post: https://smartairfilters.com/en/blog/best-materials-make-diy-face-mask-virus/
Studie don't fully recommend vacuum cleaner bags (german): https://www.unibw.de/lrt7/stroemungsanalysen-zur-sars-cov-2-schutzmaskendebatte
Swirl don't recommend there products (german): https://www.melitta-group.com/de/Statement-der-Melitta-Group-zu-alternativen-Schutzmasken-3605,263.html
sterilization wrap: https://products.halyardhealth.com/surgical-solutions/sterilization-solutions/sterilization-wraps/halyard-kimguard-one-step-sterilization-wrap.html
Link:https://youtu.be/DZBbkn-g-vE
How hepa works: https://www.alencorp.com/blogs/articles/air-purifiers-and-coronavirus