CO2 is what is produced AFTER you burn fuel (along with a whole host of bad chemicals) it is non flammable, & if you read the instructions on just about ANY CO2 kit it will tell you to keep the intercooler sprayer away from the intake pipe.
If you are keen on spraying something into you intake to cool inlet temps, as stated above go with nos, or water/methanol injection, or even propane(starting to get big in the states for drag cars).
Otherwise, if you already have the CO2 kit & are keen on using it set it up so that it sprays ONTO the intercooler or a intake pipe.
Just a side note that they make kits that have a teardrop shaped bulb inside a pipe which is fitted into the intake piping. when the CO2 goes thru it on its way to the intercooler sprayer it gets super cold & cools the intake charge that way.
I hope this helps,
Regards,
Jeff