Hi Tom, Ray,
Answer to the question...
CO2 is "much" more heavy then air so that tend to flow to the bottom, unless vented , it can be deadly but not as CO.
In europe we have some slaughterhouses that uses a deep pit , filled with CO2, to sedate/kill the feedstock before slaughter.
CO however, is "slightly" more light then air and will flow in the upper parts of the room. Even small amounts can pose greater danger. Therefore only in open , vented spaces.
The question was a bit tricky, CO2 or CO involved, coz the fires, used in open space or as in the question, will barely produce unburned CO.
CO2 will be produced in any situation where as Carbon combusted/oxydised or where as fermentation processes take place.
First aid, and in my opinion a must have if CO is involved: Oxygen bottle for first life saving measures
The most occuring symptom for CO intoxication is headache, this is just moments before passing out, more other symptoms can also be related to other gasses, so be aware. It is not always easy noticeable !!!!!
Try to stay in a room with argon leaking bottle, you will notice some of the symptoms, but not as severe, and no headache.
Trying to keep this short and save: stay well vented... Install CO detection in your house wherever open flame is involved.