Above 8,000 feet of elevation, many people become tired and lethargic from of low oxygen levels. Mountain climbers often need oxygen masks.
Airliners And Beyond
Continuing upward, we reach 30,000 feet. Airliners cruise at this altitude, almost six miles up. The temperature is seventy degrees Fahrenheit below zero, and without a pressurized cabin, humans lose consciousness in one to two minutes from lack of oxygen.
About eleven miles up we reach the stratosphere and are now above 80 percent of the mass of the atmosphere. We're also above most types of clouds.
The Edge Of Space
In 2012, Felix Baumgartner set a record for the highest manned balloon flight into the stratosphere. Twenty four miles up, the sky was as black as outer space, and Baumgartner needed a pressure suit for protection when he skydived to earth.
More than two hundred miles up in the vacuum of space, where the International Space Station is in orbit.Â Besides providing air pressure and oxygen, at this altitude a spacewalking astronaut's suit must protect against temperature extremes, bullet like micrometeorites and radiation!
- Atmosphere Of Earth (Wikipedia)