Scuba divers are warned that if they must make a rapid ascent, they should exhale on the way up. If a diver rapidly ascends to the surface with lungs full of air, his lungs could be damaged. Explain why this is so.

Air for a diver comes out of a high pressure tank at - Same - pressure compared to the water around the diver (metered by the regulator).

This means the lungs are inflated with - Highly pressurized - gas.

This does not adversely affect the diver when deep underwater, because the entire environment around the diver is at - Same - pressure.

If the diver suddenly surface, the air in the alveoli in the lungs will still be at - a higher - pressure compared to the air around the diver, which will be at - a lower - pressure.

The gas in the diver's lungs will - expand - and can damage the alveoli.