Which would be a rational argument if known humidity increases weren’t noted in every case of mask use. My argument is that making contained environments that are known to increase humidity and have been seen to make levels that restrict lung oxygen volume. Sitting in a steam room with a mask vs without one will cause a noted difference in lung function due to unnatural levels of heat and humidity. Adding to this is the increased pressure on breathing through a mask vs no mask and there is a very real reason to be concerned with hypoxia.