Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Thin Air Breathing
Name: Amy
Location: N/A
Country: N/A
Date: N/A

Why is it hard to breathe in thin air? What health dangers do mountain climbers face at high altitudes?

Among the obvious dangers of losing ones footing, the oxygen available in the air is considerable less at higher altitudes. If I recall correctly, 21% of the atmosphere at standard temperature and pressure at sea level is composed of oxygen. This is less at higher altitudes. One can lose consciousness and even die in an oxygen deficient environment with changes from oxygen content to lower than 19.5%. This can unfortunate effect can occur within minutes.

Dr. Myron

The air is not really thin at high altitudes. The problem is that air pressure is lower. As altitude increases, air pressure decreases. In order for your lungs to fill with air, the air pressure in your lungs has to be less than the pressure of the air outside your lungs. Air moves from areas of higher pressure to lower pressure. As your diaphragm (the muscle that separates your chest cavity from your abdominal cavity) moves downward, the size of your chest cavity increases. This decreases the pressure in your chest and air flows in. When the diaphragm is up, it puts pressure on the chest cavity and the pressure in the lungs is greater than outside the lungs. Air flows out. This is an example of Boyle's Law. The movement of the diaphragm is controlled by the brainstem. Anyway-the reason that it is harder for some people to breathe at higher altitudes is that the air pressure differences aren't as great between the inside of the lungs and outside.

Van Hoeck

Click here to return to the Biology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory