What is partial pressure of CO2 scuba diving?

Answer 1

Let's start with understanding the question. Partial pressure is defined as the fractional percentage of the gas in the overall gas mixture times the total pressure in Atmospheres. If we assume we're Scuba diving using air as our breathing gas, then the fractional percentage of nitrogen is 79% (or .79). Oxygen make up the majority of the balance at 21% (.21) Air is made up primarily of these two gasses. All other gasses that comprise air are considered "trace" gasses. Carbon dioxide is one of these trace gases, and accounts for about 0.039% percent of air by volume.

If we assume for a moment that we're at sea level, then the total pressure, by definition, is 1 Atmosphere (atm). This means that the partial pressure of nitrogen in air at sea level is .79. Oxygen is .21. Carbon dioxide is .00039.

Every 33 feet a diver descends in sea water adds one additional Atmosphere to the Total Pressure. This means that Total Pressure at 33 feet is 2atm and at 66 feet is 3atm. PPO2 (partial pressure of oxygen) at 33 feet is .42. PPN (nitrogen) is 1.58. PPCO2 (carbon dioxide) is .00078. At 66 feet of sea water PPCO2 is .00117 (.00039 X 3atm).