It was not a trick question that I asked my fifth-grade students long ago.
"How can CPR revive a person if we breathe IN oxygen and we breathe OUT carbon dioxide?"
After some guessing, one student came up with the correct answer. "There is still some oxygen left in the air we exhale."
Yes there is, and while the ratio is different, it is sufficient to get the job done.
I offer this anecdote in response to persons who seem convinced there are mortal dangers to wearing a face mask. No, you absolutely will not poison yourself with your own carbon dioxide emissions. Any fabric which lets you breathe in will just as easily allow you to breathe out. Think of medical personnel involved in complicated surgeries which could take hours to perform.
Mask wearing, hand washing, and social distancing are the critical components of reducing this pandemic. Please observe them during this extraordinary crisis.
I'm Jim Kline, and that is my Perspective.
