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Author(s): Nancy Moreno, PhD, Barbara Tharp, MS, and Judith Dresden, MS.


When we breathe inward (inhale), air from outside enters our airways and lungs. As demonstrated in the activity, “Breathing Machine,” breathing is a mechanical process, driven by changes in the volume of the chest cavity. The air taken in with a normal breath represents only part of the total amount of air the lungs can hold. Likewise, the amount of air normally breathed outward (exhaled) represents just a portion of the total amount of air that can be expelled.

The maximum amount of air that can be blown out of the lungs after taking a deep breath is known as vital lung capacity. But some air always remains in the lungs and airways.

Diseases of the respiratory system affect lung volumes and capacities in many different ways. Some diseases reduce the lungs’ vital capacity. Others cause changes in the amount of air held in the lungs after air is blown out forcefully.

Note: A spirometer is an apparatus for measuring the volume of air inhaled and expelled by the lungs. It is used to rule out different respiratory diseases and can help find the cause of shortness of breath, effects of contaminants on lung functions, effects of medication, and progress for disease treatment.

Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education