Originally Posted by TQA
Hmm well you should look up hypercapnia [excess CO2] which is a known problem with long snorkels.
I am afraid that you are a victim of Wikipedia bunk. That particular little argument from a 1952 Navy study was debunked back in the 80s ... again by the Navy. A snorkel that is too long will starve a diver simply because of the pressure difference ... not the CO2.
The CO2 question was studied extensively because of commercial hard hat diver incidents that occurred. Because the air circulation in the hat was not sufficient to expel the diver's breath, the diver would slowly but surely go to sleep and if not tendered properly, could die. I was an expert witness on a trial where a diver died for that very reason.