2 pieces only (plus an optional head strap for the rubber band)

3 hour (2.5hr for thin-wall version) print time (Prusa i3, PETG, 0.3mm layer, 20% infill, 3 perimeters!)

Requires some form of a gasket on the inside edge for a good seal. Window seal works great. Silicone bead does too. Model contains a small ridge for easier alignment of the seal.

0.5 to 1 mm filter thickness - designed to be used with cloth, nano fabric or other types of thin filter materials.

The filter needs to be roughly cut to size. Snap-on filter cover holds it in place and creates a reasonable seal around the perimeter.

UPDATE 9/4/2020:

Added a thin-wall version of the facepiece (still fits the same filter caps). 1.2 mm uniform thickness of the wall yields 3 3 perimeters on printer with 0.3 mm nozzle. Reduced print time (to 2 hrs), material cost and weight. Durability in PET-G seems sufficient.

UPDATE 7/4/2020:

A second option for the filter cover designed for a round (57 mm diameter) foam cosmetic pad as a filter. The pad circumference needs to be pushed into the groove to fit and create a sufficient seal.

A third option added per suggestion from Mr. Calin Caparu - An alternative facepiece without a filter cover. Fabric- or paper-based filter is wrapped around at least 1 cm and secured to the mask via rubber band, which should be tight in the corresponding groove around the air intake. Apparent pros: Single piece, no worry of losing the cover, no possibility of bad fit between the facepiece and the filter cover due to different printing margins. Apparent cons: Needs a suitable rubber band, requires a larger piece of the filter.

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This is my take on the facemask. There are plenty of other models on Thingiverse and around the internet, but I usually had issues with:

• Long print time
• Too much bulk

and most importantly

• Very hard to breathe with a good seal!!

Full disclaimer: THIS IS NOT TESTED FOR PROTECTION!

The protection certainly varies depending on the filter used. The main purpose of this mask is a disposable mask replacement that is relatively convenient to wear and breathe in for a longer period of time.

Let me know if you need a modified size! I can also model in accommodation for glasses if needed. My glasses work with this mask fine.

Stay safe!