Half face mask,

thingiverse

This design is inspired by Copper 3D, see their website for the original design (https://copper3d.com/hackthepandemic/) I redraw the mask because I think the thermo-forming is really a good way to do to adjust face. - Added a second valve for better breatability - Improved the thread for easier use Original instruction: Heat the mask to 55-60 °C with hairdryer or hot water. Be careful to no deform the filters parts. Adjust the deformation to your face.