Question

1. Dry air is mixture composed of 21% oxygen and 78% nitrogen. Both these gases can have negative impacts on a SCUBA diver at high pressure. For every 10 meters of a dive, the pressure increases by 1 atm.  Oxygen becomes toxic when its partial pressure is above 1.6 atm. If a diver leaves the boat at sea level (1 atm) with a tank at 0.21 atm of oxygen and dives to 40 m where the pressure is 4 atm, what is the partial pressure of the oxygen and is this toxic to the diver? If not, how deep can the diver go before the oxygen becomes toxic?

Answer 1

At 1 atm of total pressure for air, oxygen would have a partial pressure of 0.21 atm. Therefore, the total pressure of the air would be 7.6 atm (1.6/0.21 atm) for the partial pressure of oxygen to be at 1.6 atm or greater. Remember that for each 10 m of depth the pressure increases by 1 atm, but the pressure at the surface is 1 atm, so the partial pressure of oxygen in air would be 1.6 atm at 66 m (216 ft).