Exhalation begins when inhalation ends.

How does exhalation occur?

Exhalation: When you breathe out, or exhale, your diaphragm relaxes and moves up into your chest cavity. As the space in your chest cavity gets smaller, air rich in carbon dioxide is forced out of your lungs and windpipe, and then out your nose or mouth.

What are the phases of respiration?

Breathing (or pulmonary ventilation) has two phases - inspiration (or inhalation) and expiration (or exhalation).