Not really! Like others have said, it’s passive diffusion based on the pressure gradient between the air and venous blood. The partial pressure of O2 in the air we breath is about 159 mmHg, about 100 mmHg in your alveoli (average since it’s constantly diffusing), and about 35 mmHg in your venous blood. Transfer occurs in the direction of high to low, so O2 heads for the blood, and CO2 heads out to the air 50 venous to 0.3 air).