You can follow links on that page to a full text study. Conclusion is n95 use after 1 hour puts co2 and o2 out of osha's acceptable range.
Edit: from the link, emphasis added is mine
Conclusions: In healthy healthcare workers, FFR did not impose any important physiological burden during 1 hour of use, at realistic clinical work rates, but the FFR dead-space carbon dioxide and oxygen levels were significantly above and below, respectively, the ambient workplace standards, and elevated P(CO2) is a possibility.
Link to the mask study or fake news
https://pubmed.ncbi.nlm.nih.gov/20420727/
You can follow links on that page to a full text study. Conclusion is n95 use after 1 hour puts co2 and o2 out of osha's acceptable range.
Edit: from the link, emphasis added is mine
Conclusions: In healthy healthcare workers, FFR did not impose any important physiological burden during 1 hour of use, at realistic clinical work rates, but the FFR dead-space carbon dioxide and oxygen levels were significantly above and below, respectively, the ambient workplace standards, and elevated P(CO2) is a possibility.