We inhale air that is comprised of roughly 78 percent nitrogen and 21 percent oxygen, as well as a trace amount of other gases.
When we exhale, the components are the same, they just come out in different amounts. Exhaled air is made up of about 78 percent nitrogen, 18 percent oxygen, and four percent carbon dioxide, excluding those trace gases.
TL;DR
Inhaled: 78% Nitrogen, 21% Oxygen, 1% Other Gases
Exhaled: 78% Nitrogen, 18% Oxygen 4% Carbon Dioxide
