There is a myth that if u wear a mask, u breathe your own exhaled CO2. Firstly, the space between your face and the mask is 40-50mm. You breathe and exhale about 500ml of air with each breath. read more
Particle Filtration masks are so porous they don't hold CO2 or other gases inside mask from.mixng with air outside mask.Last of any breath you exhale from.lower lung called end tidal breath has approx 100x more CO2 than inhaled in fresh air (40000ppm vs 400). read more