Hi , this is my first comment here.
I was previously writing in the "Country Club" and just been banned because of crime of not supporting vitamin A toxicity.
One of the easiest ways to increase CO2 is to buy soda stream bottle or sth of that kind ,filling big bag and going inside up to the neck . Warm CO2 has more infrared energy.
Emergency /survival way can be breathing in that bag for oxygen lowering/CO2 increase and transdermal CO2 delivery.
We must remember that we exhale also carbon monoxide during flu/"covid" from heme oxygenase-1. I don't know if carbon monoxide by transdermal way can be a big problem.
CO2 among others recycles K1/K2, detoxifies ammonia to urea, pushes out carbon monoxide even in coma out of heme.