
Physiological impact of N95 mask on healthcare workers - simonebrunozzi
https://pubmed.ncbi.nlm.nih.gov/20420727/
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captainredbeard
> Two subjects had peak P(CO2) > or = 50 mm Hg. The FFR with exhalation valve
> offered no benefit in physiological burden over the FFR without valve. The
> FFR dead-space oxygen and carbon dioxide levels did not meet the
> Occupational Safety and Health Administration's ambient workplace standards.

While the rest of the study said 1hr of typical healthcare worker activity was
not a problem for functioning, this part is somewhat alarming.

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cameldrv
The fact that the dead space air doesn't meet OSHA standards for ambient air
is a red herring. When you breathe out, you're filling up the mask with your
exhaled breath. When you breathe in, you'll breathe in most all of the dead
space air, and then fresh, filtered air. They measured tidal volumes of about
900ml, and the average N95 mask dead space is 125ml. Therefore, about 15% of
the inhaled air will be air that was previously exhaled.

What they found was that the dead space CO2 was about 3000ppm. Suppose they're
indoors and CO2 is 700ppm. The mask increases CO2 to 1045, which is still well
within an acceptable range.

