A bell jar model can be used to demonstrate how breathing works by showing how changes in chest cavity volume and pressure cause air to move in and out of the lungs. Pulling on a rubber sheet represents diaphragm contraction (inhalation), while pushing it up represents diaphragm relaxation (exhalation).

1. Place two balloons inside a bell jar and connect them to a Y-tube, which passes through a bung at the top of the jar.
2. Stretch a rubber sheet over the open bottom of the bell jar to act as the diaphragm.
3. Pull the rubber sheet downward to demonstrate inhalation: the increased volume lowers air pressure inside the jar, causing air to enter the balloons and inflate them.
4. Push the rubber sheet upward to demonstrate exhalation: the decreased volume raises air pressure inside the jar, forcing air out of the balloons so they deflate.

Bell Jar Lung Model Video - Dr Dan's Anatomosphere:

Bell jar model of the human breathing system - Sean Clifford:

📄 Modelling the Mechanism of Breathing - Beyond Science: https://europeanlung.org/wp-content/uploads/2023/12/Modelling-the-Mechanism-of-Breathing-Teacher-Demonstration-Guide.pdf

• Add labels or color-coding for trachea, bronchi, lungs, diaphragm, and thoracic cavity to reinforce anatomical connections.
• Modify the model by adding a moveable “ribcage” structure to show the role of intercostal muscles in breathing.

• Handle glass jars carefully to avoid breakage.
• If using sharp tools to cut or modify equipment, supervise closely.
• Ensure the rubber sheet is stretched securely to avoid snapping.
• Do not inhale directly from balloons or tubing used in the demonstration.

• What causes air to move into the lungs during inhalation?
• How does the diaphragm contribute to changes in air pressure inside the chest?
• Why do the balloons deflate when the rubber sheet is pushed upward?
• What limitations does this model have in representing real breathing?
• How would this process change if the diaphragm or intercostal muscles could not function properly?