I was thinking... that since propane is like NOS, it would work better if it were purged. I figure it'll make the same cool sound and show as the NOS when vented. I was thinking of spraying mine out near the turbo.
Nitrous is injected as a liquid and not as a gas. That is why the need for a purge valve.
Nitrous is NOT flamable.
Propain is being injected as a gas NOT as a liquid, so no need for a purge valve.
Propain is very FLAMABLE.
One spark or enough heat near where you vent and you better have your flame suit on.
Just my 2 cents.