Well first off, to see if there is actually carbon dioxide present, you can use phenol red. If you heat the solution, the vapors will... evaporate into a tube. Put a tube into a solution of phenol red. If there is carbon dioxide, the phenol red will turn yellow. You could also use lime water, but that is a bit more tricky, and can also be dangerous if not handled with care
To see how MUCH CO2 is present:
One method is a gas train of flasks. One flask contains an aqueous solution of sodium hydroxide of a known concentration. Air is bubbled through the sodium hydroxide for a given amount of time. The concentration of the sodium hydroxide is determined by tritration. The data is inserted into a formula and the result is the amount of carbon dioxide present in the air. I don't have the reference books available to be more specific.