What is the paial pressure for oxygen in the inspired air?

Paial pressure of O2 in inspired air (Pi O2) - 158 mm Hg Gaseous concentration & its paial pressure in alveoli: 1. Oxygen: Concentration & paial pressure controlled by, Rate of absorption of O2 into blood Rate of entry of new O2 into lungs by ventilatory process. Values: Paial pressure of O2 in inspired air (Pi O2) 158 mm Hg Paial pressure of O2 in alveolar air (PA O2) 100 mm Hg Calculated by "Alveolar gas equation". Paial pressure of O2 in expired air (PE O2) 116 mm Hg 2. Carbon-di-oxide: Paial pressure of CO2 in inspired air (Pi CO2) 0.3 mm Hg Paial pressure of CO2 in alveolar blood (PA CO2) 40 mm Hg Paial pressure of CO2 in expired air (PE CO2) 32 mm Hg