The whole publication is a joke. It goes on and on about breathing "2.8–3.2% carbon dioxide" when mask dead space constitutes maybe 15-30% of human tidal volume

The whole publication is a joke. It goes on and on about breathing "2.8–3.2% carbon dioxide" when mask dead space constitutes maybe 15-30% of human tidal volume. At rest. And I'm pretty sure "2.8-3.2%" is a cherrypicked datapoint, other studies report lower concentrations. Realistically, all of this is less of an issue than classroom CO2 exposure over a schoolday but nobody's acting outraged about that one for some reason.