Following this Blog post, I was asked "how do you store your opened packs of DAS?"
I tend to use two methods;
The first is using these zip-lock bags (this example is from IKEA but similar bags are available from most supermarkets. I suggest you look out for the double seal bags with two sealing strips across the top as I find these are better).
The second method is a little old school, just a bulldog clip or clamp to keep the opened pack sealed shut.
I hope that this helps.