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Since the dawn of COVID-19 pandemic, I have been personally exploring my masksâ ambiance. After documenting in-mask heat and humidity objectively determined with Hygrochron iButton DS1923 in my face covering [1], I had been wondering whether my in-mask micro-climate will differ (A) if simple mask vs. valved mask vs. N95 mask, and (B) if indoor vs. outdoor. Hereby, image (A) is my in-mask micro-climate over one-hour period on day-(A) with simple mask, valved KN95 mask, and surgical N95 mask, worn for 20 minutes each. Subsequently, image (B) is my in-mask micro-climate over one-hour period on day-(B) with simple mask covering surgical N95 mask (dual mask) worn while indoor with no air changes, indoor with some indeterminate air changes, and outdoor, for 20 minutes each. Irrespective of mask type or ambient environment, images (A-B) demonstrate variable but definite in-mask increases in temperature and relative humidity as measured by Hygrochron iButton DS1923 and absolute humidity as calculated by online calculator [2]. Moreover, based on variabilities in entrapped heat and humidity under mask and such microclimatesâ corresponding efficacy to potentially inactivate SARS-CoV-2 [3-5], I can hypothesize that my hypothesized âtherapeuticâ effect of in-mask micro-climate against âcoldâ viruses may have variable onset and effectiveness according to mask type [6]. However, it remains to be seen if (and how) barometer readings change under mask, indoor vs. outdoor, considering barometric pressureâs effect on calculated absolute humidity [2], because as noted while outdoor (B), calculated absolute humidity did not budge much as compared to indoor even when measured relative humidity increased in response to decreasing temperature outdoor as compared to indoor. A point worth noting may be that, during heated and dried indoors during winters, the problem may be the low absolute humidity created by cold outdoors whereby heating the indoors further drastically decreasing indoor relative humidity due to the low absolute humidity therein to begin with. However, this problematically low absolute humidity too may somewhat get countered by the somewhat stability in the absolute humidity exhaled by bodies within the masksâ enclosed microclimates irrespective of ambient climatesâ labile temperature, labile barometric pressure and labile humidity, outdoors or indoors [7].    FIGURE A-B
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