The air they are breathing IS at least 19.5% oxygen.
However, dumb people are wearing masks, so are re-breathing part of their own exhaled CO2... and their oxygen intake is reduced to about 18%. Nothing happened to the oxygen available... but simply the dumb people wearing masks are depriving themselves of it.
The air they are breathing IS at least 19.5% oxygen.
However, dumb people are wearing masks, so are re-breathing part of their own exhaled CO2... and their oxygen intake is reduced to about 18%. Nothing happened to the oxygen available... but simply the dumb people wearing masks are depriving themselves of it.
I think you mean "they" being mask wearers "are breathing IS at MOST 19.5% oxygen".
Otherwise, its simply not true and can easily be verified.