3M 7500 mask exhalation valve

this small design was made for make your exhale filtered as inhale.With this mode your mask start to protect people around you if you infected and don't know about that.

HOW TO USE: Just add some filtering material like surgical mask (proper side!) or cotton disks (not recommend) and fit two parts together. I recommend to change filter every time before you leave/
Installation process: https://youtu.be/UxBEbYAQROk

In some countries health department prohibit to use respirators as they don't protect people around person who wear a respirator. Using this filter box with usual surgical mask or other filter material could help you to filter your exhale and de-facto explain to police why you can use respirator.

feel free to fit this design to your needs. I printed it from PETG and it fits as it is. But fit is very tight, may be you will need to scale second part down to 99%

Keep in mind that all DIY mask mods you use on your own risk. Also I recommend to use sealant (liquid of PFTE ribbon) for make it really tight fit without spaces to leave "infected" exhale leave.

Current design included 3 versions:

1. Surgical mask only - most smallest and fastest to print. Adapted to use only with surgical mask piece
2. Big box - presented on photographies. Could be use with cotton and surgical mask at the same time.
3. Test design, that adapted for use in 12hours shifts. On tests now. Really big and adapted to keep mask pieces dry for a longer time.