More specifically, your exhale is 78% nitrogen, 16% oxygen, 4% carbon dioxide, and about 0.08 Argon.  Try to keep these percentages in mind while I explain the extraordinary workings of our lungs.  Nitrogen(N) and argon(Ar) gas are not used by our lungs. So the exact same amount is exhaled as breathed in (except for maybe very small trace amounts).  Atmospheric air contains 20.95% oxygen. Every breath we take, our body uses 4.95% O2. Now, this doesn't sound like allot, but it actually is.  Atmospheric air consists of only 0.0394% CO2. Our CO2 in our exhale is 102 times the amount of CO2 in the atmosphere we breath in.  Now, let's look at wearing a mask. Immediately after putting the mask on, your second breath of air is reduced as a result of the build-up of CO2, N, and Ar in the mask. N and Ar can be considered a constant since your lungs don't absorb it. But, the CO2 is absorbed and every inhale it is absorbed at a higher percentage.  The red blood cells prefer O2, but it will be forced to carry CO2 if O2 is not available. CO2 is critical in trace amounts to maintain a functional cellular PH level (cellular voltage = -25mV). The PH scale runs from 0 (+400mV) to 14 (-400mV). Anything "+mV" is acidic, whereas anything "-mV" is alkaline. When CO2 builds up in the bloodstream and subsequently in your organs, the PH level 'acidifies' and Acidosis results. Cellular health is maintained at -25mV. When you are sick, your cellular voltage is measure around -10mV. This when viruses and other pathogens have overrun your immune system defenses.  As cellular PH levels reach 0 volts and continues to become more acidic where your cellular PH level becomes +30mV, this is where cancer exists. This is why wearing a face mask is in violation of OSHA safety standards, specifically 29 CFR §1910.134. The OSHA Director of Safety Programs stated that the scientific research conducted by OSHA establishes that having an oxygen level below 19.5% may be deadly, or result in organ failure and severe bacterial infections (e.g. pleurisy). Wearing a muzzle immediately reduces oxygen flow well below 19.5%, in clear violation of OSHA safety standards.  The government already knows face masks are harmful and dangerous. It is well established science that is being covered up. It's a CRIME Against Humanity.