Comfortable Covid Mask

I used the blender add-on called facebuilder, to fit my face custom. However, you can easily customize it to your face, by putting it in hot water and shaping it to fit. Also, as of 7/22/2020 I added some files and instructions for scaling the print to your face. I designed it to use thin elastic for the straps, because that's what I had access to, but use whatever works. Elastic shoe laces work very well for straps.

I recommend printing it with 100 - 150 micron layer height, to try and create a better seal. you could also use food safe epoxy to seal holes in a lower quality print.

Some people are concerned that because the virus is so much smaller that 0.3 um that they think it's like, "trying to stop grains of sand with a chain link fence" but the physics of filtration is not that simple.
Here's a good paper on what size particles have the greatest penetrating ability for HEPA filters:
https://www.osti.gov/servlets/purl/6241348

Notice that bigger, and even the smaller particles, than 0.3 um particles are filtered. In fact that is the reason they specify the 0.3 um for the particles that are blocked, because that is the particle size that is most likely to get through. The smaller particles are caught due to Van Der Waals forces. Also, notice their experimental results show that filters are worse for faster velocity of air through the media (makes sense). So my idea was two-fold, make it easier to breath and, by Bernoulli's principle, slow the velocity of air through the filters, I did this by increasing the area of the inlets.

Using HEPA filters may not be a good option due to the large differential pressure needed in order to breathe through it. The good news is that filtration physics principles remain the same for the most part with other filter media. So, for filter media to use, you should visit: https://www.maskfaq.com/test-results

They use NIOSH approved equipment and they show promising results for commonly available materials. As of 7/23/2020 the best option they have found is "Filti" brand filter material:
https://filti.com/product/filti-face-mask-material/

the 21 square feet option is $30 at the moment, and it's plenty to last for a long while (I'm not affiliated, I just personally recommend it).
When you use two layers stacked, it passes the N95 NIOSH standard. But also take note of what happens to the filter efficiency when you wash the 2 layers... It drops from 97% way down to 45%!!! So don't wash your filters, just replace them.

Take all of this with a grain of salt, I have no way to quantify the ability of this mask to protect you. It depends on what filter you are able to use, how good of a hermetic seal you are able to achieve (test by holding the mask on your face and without filters, plugging the holes with your hands and breathing in or out), and how good your mask wearing etiquette is, how well you clean it for reuse, etc.. I do believe, if nothing else, it can be pretty effective for protecting others, by catching condensation from your breath, catching your coughs and sneezes, and keep you from touching your face. However, recent studies have shown wearing even a rudimentary mask will protect you.

This design also accommodates glasses fairly well without fogging.

UPDATE (6/24/2020):
I got rid of the slits in the filter caps, this made them much more durable. Watch for filter caps and the mask both with a supportive grid (to keep the filters from flapping/popping), it's coming soon.

UPDATE (6/25/2020):
I just went ahead and added the supportive grid for the filter media (you'll want to print "Mask3," "HeadStrap," "RightCap4," and "LeftCap4"). I left the legacy version just in case. Enjoy.

UPDATE (7/22/2020):
I felt bad for people who don't have a horse face like me, so I added a zip folder with files and a guide so you can scale the latest version to fit your face better.

UPDATE (11/4/2020):
I made the caps flat on the one side for easier printing. I also updated the scalable version to include the new cap version.

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