A doctor proved on a video that wearing a mask does not raise your CO2 levels at all.
He was shown wearing an oxygen monitor which was registering his oxygen level at 98% without a mask, (reason given for being 98% was he was slightly nervous being filmed and nerves reduce your intake. Hence when some people get nervous, or scared, they can hyperventilate). He then wore a mask for 5 minutes and his level remained at 98% so that throws your argument out of the window.
Did he wear the "mask" around his neck, or have his nose poking out?