Refilling those pluggin air freshners?

The problem with these things are you pay say �2.00 for the pluggin and refill, but once its done and you go to buy a refill on its own its �3, so the obvious solution is to buy a whole new unit. Well I have been doing this and now have quite a collection of empty refills. Now if I picked the top of the refill could I refill it myself? Say from the contents of a spray air freshener? It does say flamable on the side of the tin but I sprayed some on a counter and tried to light it with a lighter and it wouldn't ignite.