Can a human breathe in an atmosphere that has a gas other than nitrogen?

FtlIsAwesome

Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%.
From Wikipedia, Earth's Atmosphere

Is possible for a human to breathe in an atmosphere that contains 21% oxygen, but has a different inert gas other than nitrogen?

Also, how do different levels of oxygen affect us?

AlephZero

See http://en.wikipedia.org/wiki/Breathing_gas for information on both questions.

FtlIsAwesome

This page does have some information I was looking for.
I was thinking of extraterrestrial planets, at roughly 1 atm pressure.
So humans could breathe on a planet with 20 percent oxygen and 80 percent helium? Humans' voices would be higher pitched on this planet.
A planet with neon instead wouldn't change someone's voice.

AlephZero

The important parameter is the partial pressure of oxygen in the mixture. Helium has a much smaller atomic weight from nitrogen, so it depends what you mean by "20%". The safe range of oxygen partial pressures is quite small. The minimum to sustain consciousness is about 16%, but too much for moderate lengths of time (e.g. a few hours) is also toxic.

For example with current space technology, astronauts wearing space suits in a vacuum breathe pure oxygen at 0.2 atm pressure whcih is equivalent to the 20% oxygen in the standard earth atmosphere, but the reduced pressure makes it easier to design a flexible space suit.

Robot B9

Helium would not work. In a short time the difference in density would cause there to be too much oxygen at low altitudes as the helium tended to escape from the planet...

Oxygen/nitrogen works cause they have close to the same mass, oxygen about 16 and Nitrogen about 14. But Helium is about 4 and is, as they say, lighter then air.

FtlIsAwesome

Now thinking about it, I could've gotten a terse answer for the title question from a Google search.

Really what am asking about is extraterrestrial atmospheres and their theoretical properties, so would this post be better suited to a different catagory like General Astronomy?


Good point.
Neon might work because its number of protons+neutrons is 20.

Some isotopes that are uncommon on Earth, but stable: Ne-21, Ne-22, O-17, O-18, N-15
Some combinations of these isotopes might mix better and therefore have a livable atmosphere, but it probably doesn't matter much.

What would the color of a neon-oxygen atmosphere be, assuming the sun was a G class? Also, how would it affect lifeforms from Earth and how would native lifeforms function?