Carbon dioxide (CO2) levels can cause toxicity or oxygen deprivation when CO2 rises to 5000 ppm, which is the limit for daily workplace exposures, according to OSHA. Masks register more than 10,000 ppm in a few seconds. A paper mask and a bandana both registered over 9000 ppm, and a plastic face shield registered at 1500 ppm. Indoor CO2 air levels should be no higher than 1100 ppm inside of classrooms.
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