system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does air get drawn into our lungs by the diaphragm when we inhale? What's physically pulling the air in our nose/mouth?
gpt
The chest cavity is a cavity. It's a closed in area that experiences a change in pressure when the diaphragm pulls down.

This has a vacuum effect which pulls in air through the nose and down to the lungs. 

When the diaphragm relaxes, the pressure in the chest cavity pushes the air back out.

So, when you inhale, the diaphragm and other muscles pull down which decreases the pressure in the chest cavity and draws air down through the available openings.