Human Lung Demonstration Model

Quick Answer: The human lung demonstration model is a working teaching aid that shows breathing as a change in chest volume and air pressure: when the model’s chest space is enlarged, air flows into the lungs, and when it shrinks, air flows out. It is used in school biology and physiology lessons on ventilation.

Negative-Pressure Breathing Made Visible

Humans breathe by negative pressure. The diaphragm contracts and flattens and the rib cage moves up and out, so the chest cavity grows, the pressure inside the lungs drops slightly below atmospheric pressure and air is drawn in. A lung demonstration model reproduces this chain of cause and effect so that students can watch it rather than memorise it. Demonstration models are built in more than one way, often as a sealed transparent chamber with elastic lungs and a movable diaphragm or plunger, and the construction of this listing should be confirmed at enquiry.

The contrast with artificial ventilation makes a useful extension. Rescue breaths and most hospital ventilators push air into the lungs under positive pressure, whereas a natural breath pulls it in. Historic iron lungs worked the other way round, lowering the pressure around the patient’s body so that the chest expanded, which is the same principle the model shows.

The model also helps with a common mix-up of terms. Breathing, or ventilation, is the mechanical movement of air in and out of the lungs; respiration is the chemical process in cells that releases energy from glucose. Students who watch the model inflate are seeing ventilation only, and gas exchange in the alveoli and respiration in the cells happen beyond what any breathing model can show. For the classic glass-jar version of this demonstration, see the lung model in a bell jar.

Lesson Uses

• Showing inhalation and exhalation as a sequence of volume and pressure changes
• Separating the ideas of ventilation, gas exchange and cellular respiration
• Comparing natural negative-pressure breathing with positive-pressure rescue breaths
• A starting point for a practical in which students count their breathing rate at rest and after exercise

Specifications

Care & Handling

• Operate the lung demonstration model with slow, even movements; jerking the diaphragm stretches the elastic parts and weakens seals.
• Check before each lesson that the lungs still inflate, since a small leak stops the demonstration working.
• Keep rubber and balloon parts out of sunlight and away from heat, which make them brittle, and replace perished parts as needed.
• Wipe transparent parts with a soft cloth and plain water to avoid scratches that cloud the view.

Why Choose LabEquip

Science teachers usually want a breathing model that works reliably in front of a whole class. LabEquip supplies the lung demonstration model within its biology lab products range; send your class numbers and any preferred construction through the LabEquip contact page.

Frequently Asked Questions

What is negative-pressure breathing?

It is the way humans normally breathe. The chest cavity enlarges, the pressure in the lungs falls just below the pressure of the outside air, and air flows in to balance it. The lungs are filled by suction rather than by pushing.

How is breathing different from respiration?

Breathing, or ventilation, moves air in and out of the lungs. Respiration is the set of chemical reactions in cells that release energy from glucose. The model demonstrates only breathing.

Why do the lungs deflate when the diaphragm returns?

The chest space becomes smaller, so the pressure inside the lungs rises above atmospheric pressure and air is pushed out. At rest this happens without muscular effort, as the diaphragm relaxes and elastic tissue recoils.

What was an iron lung?

An iron lung was a sealed tank that enclosed the body up to the neck. Pumps lowered the pressure in the tank, the chest expanded and air entered the lungs, the same negative-pressure principle shown by the demonstration model.

Can students do a practical alongside the model?

Yes. A simple follow-up is to count breaths per minute at rest and again after light exercise, then link the faster rate to the muscle movements the model represents.

How is it different from the bell jar lung model?

The bell jar model is one specific design, with balloons in a jar and a rubber sheet as the diaphragm. A demonstration model shows the same principle but may be built differently, so compare the construction of each before choosing.

Last Updated: September 2026