Jordan Sparks and Chris Brown's song is about how they can't be away from each other because if they are they feel as though they wouldn't be able to survive.

But how do you expect me
to live alone with just me
'Cause my world revolves around you
It's so hard for me to breathe

[Chorus:]
Tell me how I'm supposed to breathe with no air
Can't live, can't breathe with no air
It's how I feel whenever you ain't there
It's no air, no air
Got me out here in the water so deep
Tell me how you gonna be without me
If you ain't here, I just can't breathe
It's no air, no air

In this song, the tone seems more so as them being desperate. They want each other so bad that in their minds, they think they would die if they can't be with one another. My favorite part in this song is when they sing the chorus together because when you listen to it you can hear the desperateness in their voices.  

Sparks, Jordan. "No Air." azlyrics. Ed. Williams, Lindsey. 2000-2012. <http://www.azlyrics.com/lyrics/jordanspark/noair.html>