Arguing with blood oxygen saturation is prety much strawman. Nobody here claims that facemasks impact that. Effects of insufficient CO_2 elimination are much ea

Arguing with blood oxygen saturation is prety much strawman. Nobody here claims that facemasks impact that. Effects of insufficient CO_2 elimination are much earlier. If you were in badly ventilated room with 2000 ppm CO_2, you would feel dizziness even that you would still have full oxygen saturation.