A New Method for Evaluating the Effectiveness of Plastic Packaging Against Radon Penetration

Deposition of $^{222}Rn$ daughters onto detector materials pose a risk to ultra-low background experiments. To mitigate this risk, a common approach is to enclose materials in sealed plastic bags made of films known to be an effective barrier against radon. We describe a method to evaluate not only the intrinsic resistance to radon penetration of different plastic films but also the integrity of bags fabricated from these films and sealed following some protocol. We report the results of applying this method to sealed bags fabricated from polypropylene, Nylon, Mylar, metallized Mylar, FEP, and PFA.