Subject: Is the reason carbon dioxide does not settle-out is due to air currents?

The Merck index shows the density of carbon dioxide to be 1.527 @ 25C, 
with air = 1.00.  The molar percent is 0.033 in the atm.  The Merck 
index states that carbon dioxide will accumulate in low lying areas 
with inadequate ventilation.  

Is the reason the carbon dioxide does not accumulate on the surface of 
the Earth due to air currents caused by the rotation of the Earth?

The question came from one of my students when we were pouring carbon 
dioxide gas from dry ice out of a beaker to put out the flame of a 
candle.  When asked why, they came up with more dense because of 
temperature.  Then we let the jar  warm to room temperature and it 
still worked.  So then the students came up with "carbon dioxide" is 
more dense than air.  Then the question came, "why doesn't the carbon 
dioxide pool on the surface of the Earth and kill all of us"?  

I answered with "mixing due to air currents", but I have not read 
anything source for this.  I told the students I would check and get 
back to them.

Thanks for your help.

Re: Is the reason carbon dioxide does not settle-out is due to air currents?