Nope. It should be perfectly safe.
The argon is not what kills you in an exit bag. The lack of oxygen kills you. With the exit bag, you create a small environment around your head where there is no oxygen. You use a gas like argon to replace the oxygen so you can feel like you're breathing normally. There is already argon in the air we breathe normally. It's an inert gas and not harmful.
If some of the gas got into the surrounding environment, it would just mix with the air around it, which contains plenty of oxygen for others outside of the confined environment of the exit beg.
