I tried the BolivAIR mask in PLA. It was good but stiffness in PLA meant the fit wasn't ideal for some faces (even with a rubber seal on the edge).

I decided to try flexible filament (TPU). With the flexible filament the mask tray is more likely to pop out which obviously defeats the purpose of the mask. Securing the tray with silicone works but it's not convenient for frequent replacement of the filter.

Added legs to secure the filter tray with rubber bands (in a crisscross pattern, see photo).

• Software:
  Repetier Host with Slic3r
  Filament: TPU 1.75 mm

• Settings Summary:
  1.75 mm TPU in with a 0.4 mm nozzle (steel)
  Use retraction (2 mm) and avoid crossing perimeters
  60 C heated bed
  220 C extruder temp
  0.2 mm layer height (0.35 mm first layer)
  3 perimeters
  5 top & bottom layers
  10% infill (rectilinear)

• License:
  Keeping the License the same as the original BolivAIR design

<<< DISCLAIMERS >>>
This model has not been approved by any regulatory agency. Use it at your own risk, and only as a last resort, if you do not have any other homologated protection. The recommended measures to protect yourself from infection with the coronavirus COVID-19 are the following:

• Stay home and avoid contact with other people
• Avoid touching your face with your hands
• Wash your hands very often

Note: This model only includes the mask structure (2 pieces) but does not include the required filter to effectively block the spread of the virus. Also, additional isolation measures could be required to properly fit the face without air gaps. Please check the comments for more information shared by other users about the types of filters that could apply to a mask with these characteristics. The effectiveness of P3 particle filters has been mentioned, and probably also HEPA 12/13, but unfortunately we do not have the means of analysis necessary to confirm this with guarantees. Again we remind you to use this model at your own risk.