Hello Steve,

This is an incomplete picture. Please look at "lung volume" capacity in Wikipedia. It will show all the different named volumes in the lung. The Tidal volume is way smaller than the Total Lung Capacity. So a 90/10 ratio in your calculation is a good starting point as an indicator but will need to be refined.

Also, nobody has mentioned that there are limits in the amount of time you can spend in any atmosphere. This is well documented by OH&S. For CO2, the fifteen minute NIOSH limit is ~30,000 ppm exposure for the day. So you can get away with wearing these masks but only for a short while. What is that exposure time? The KN95's are the best for filtration but the worst for pressure drop across the mask. This means the lung experiences an increase in air pressure which ultimately results in less flow.

This would be a great interdisciplinary study to figure out what would be a "safe" amount of time to wear a mask (with different pressure drops up to including a plastic bag over the head) without experiencing detrimental health effects. Has NIOSH done this already? Where did the 30,000 ppm 15 minute limit come from?

Wayne