Posted for "Ted Noel" <tednoel@cfl.rr.com>:

 Suppose you have an steady flow of CO2 into the cabin from the cooler. If
your cabin is sealed, the cabin pressure will rise and the concentration of
CO2 will rise.
 
 BUT...
 
 If you have any reasonable amount of ventilation, the probability that this
will cause a problem is close to nil. And the last time I checked, a Legacy
was unpressurized. I suppose that if you kept the cooler in your lap with the
lid cracked next to your face you might have a problem, but it wouldn't be the
CO2.
 
 In short, relax. CO2 isn't like CO. CO binds almost irreversibly with
hemoglobin, and is deadly in very small concentrations. CO2 is something you
breathe out constantly. It is highly soluble, and it is very easy to get rid
of excess amounts.
 
 Ted Noel MD
 N540TF