So if the average sensor reading is accurate would one expect the PPM reading in an N-95 mask to reach (38000+4,340)/2 ? Is there an appropriate sensor? Check out Vernon Coleman’s latest video on masks here: https://vernoncoleman.org/videos/chronic-maskitis His referenced book: https://vernoncoleman.org/sites/default/files/2021-03/proof-that-face-masks-do-more-harm-than-good-v2.pdf Some of his notable points: 12. OSHA as decreed that any room where the carbon dioxide is present at a level or more than 5,000 parts per million is unsafe and has an environment which is toxic and dangerous. 19. OSHA states that any human-occupied airspace where oxygen measures less than 19.5% should be labelled as not safe for workers. However, the percentage of oxygen inside a masked airspace generally measures 17.4% 35. N95 mask can reduce blood oxygenation by as much as 20% and this can lead to a loss of consciousness.