[jimjamuser]

Originally Posted by golfing eagles

Did you read the OP fully, Inex, and how did you not laugh?. Unbelievable---someone picked up the term "dead space", probably from the internet, and then throws it around like they have any idea what it means. Since the mask will be in close proximity to your lips, it does not increase dead space. (the OP's statement was "Apparently breathing CO2 from wearing a mask increases dead space", which is even more absurd). If someone had end stage COPD the added layer of obstruction MIGHT add to CO2 retention, but those people are generally on supplemental O2 anyway and not wearing paper masks.
Someone else posted that MOST people don't expel all the air when exhaling. How about ALL people, and all land mammals as well, otherwise we'd have total lung atelectasis.
A little knowledge...………….

Good post.