Are you sure you're taking into account the cost to the environment of exhaling? CO2 is a deadly gas, and while the air might be technically "free," the fact is, every time we breathe, we emit deadly global greenhouse gases.

It's the exhalation we should tax -- and heavily!

To save the planet!

Don't forget oxygen bars.

Oh yea on your post a few weeks back on carriers doubleing up in the Mideast.

You were right I was wrong.

I remember an old Donald Duck comic book.

Somehow Sharkey The Lawyer got Donald (it involved a lawsuit against Eric The Red) to agree to charge for oxygen breathed and measured by a mandatory oxygen mask.

The advertising line went:

"A gasp - ten cents;
A wheeze - one quarter;
A Deep Breath - Call for an estimate."

Same idea as you described, Eric...