But before we use a roll slow, we must assume that there is dynamic equilibriums between the gas molecules in the space above and the gas molecules dissolved within our blood. So let's make that assumption. Now, we can find the partial pressures of each gas by simply using the formula. Now, before we use the formula, let's let's realize why we're using 760 mmhg. So the total pressure above our system is the air that we're breathing in is the pressure of the air that we're breathing in. And the air we're breathing in is at atmospheric pressure.