RV daytrader wrote:
CO2 is odorless....you may be smelling something, but its not CO2. 
CO is actually colorless, tasteless, AND odorless. Because it cannot be noticed without a detector or meter, CO has earned the dubious name of “silent killer.” When folks call and say they can “smell carbon monoxide,” they are usually referring to other combustion byproducts that the human nose can detect.
This is so. You cannot smell CO (carbon monoxide).
When you blew into it, you lowered the concentration of CO, if that is the real culprit.
I’d get a stand alone CO detector and see if it goes off with the built in one.