But the air was measured to be generally 0.5% enriched in CO2 for FFP2/3 masks with peak of 2.5-3.2% in some (lower quality) N95, as they mention in their own.

But the air was measured to be generally 0.5% enriched in CO2 for FFP2/3 masks with peak of 2.5-3.2% in some (lower quality) N95, as they mention in their own. The conclusion thus does not follow, and the author is pushing some anti-masking agenda. mmHg values are quite secondary. Obviously someone so sensitive to CO2 would have to wear a portable powered respirator/oxygen concentrator with CO2 capture filter anyway, as the smoke from cars driving would wreck them.