Measuring lung volume

Lung volume is a measure of how much air you breathe in or out. You can measure it by catching the air from one big breath out.

• Fill a bottle with water and stand it upside down in a trough of water. Push a tube up into its neck.
• Take the deepest breath you can, then breathe out as much air as you can through the tube. Your breath pushes water out of the bottle.
• Read the scale at the water level. The space above it is the air you breathed out, in litres.
• People have different lung volumes. To test a claim, such as “taller people have bigger lungs”, measure plenty of people.