Quote Originally Posted by Bruck View Post
I think it's to get rid of the inert impurities that got in there the last time you filled it. Anyway, I get better results when I purge before reloading.
It also cools the lighter in the same effect as putting it in refrigerators, allowing you to fill more butane. It's called Joules-Thompson effect that also happens to can of butane when you are filling up the lighter.