I was given a handful of mask to use during the Covid crisis but they all came with easy breath exit vents. Although they'll be great for working in my home shop they be a bit of a problem out in public. I didn't want to do anything permanent to them (again, they're great in the shop) but I wanted to use them out in public (super comfortable).
For my first design I simply changed out the plug on the inside and it worked great. Easy in, easy out. Only problem is that the vent still LOOKED like a vent to everyone else. Ok, let's flip it. I redesigned the outside portion so that it mates with the original inside piece.
Boom, easy swap parts for shop use (easy breather) or public (no vent). As an added benefit I cut in the text "NO VENT" for those inquisitive enough to get a close up look.
I'll include both the original inside plug and the newer outside replacement piece.
The pictures show the test pieces. For production use I used a bright orange PLA and dropped in some black paint for the text - Bright colors and high contrast text should keep people from having to get an up close and personal view.