Fear monger often? They didn't capture any chemical weapons at all, just a place where those weapons had been kept long ago. Obviously, or the Bushistas would have trumpeted the find from every rooftop.
Sheesh.
No, there actually are chemical weapons and precursors stored at the site. The Bushistas didn't trumpet the find because the charge wasn't that Hussein had WMD - everyone and his brother knew that. The charge was that Hussein was still manufacturing and stockpiling WMD. And since everyone knew about them, it wasn't really a find. Discovering Greenland is a pretty major accomplishment, but I'm not likely to get much air time if I announce it today.
Frankly at this point the hundreds of tons of sodium cyanide stored there (for making tabun) is probably more dangerous than are the sarin rockets. Certainly it would be safer for ISIS to use - although just going down into a partially destroyed bunker containing hundreds of tons of sodium cyanide and thousands of old sarin-filled rockets would be insane. Chemical weapons MUST be properly inspected to be a viable weapon system, even though they individually remain dangerous. If containment can be expected to fail on 1% of such rockets a year (a number I happily pulled out of my ass for theoretical purposes) and no one is monitoring the rockets, then simply trying to use them is reasonably likely to kill you.
If sarin in a rocket is 90% degraded then it isn't likely to kill anyone even if properly deployed - but it's still quite potent enough to kill YOU if it ruptures as you're handling it. At that point it's still incredibly concentrated.
Having ISIS take this cache is like when they captured the radioactive uranium - it makes splashly headlines, but it doesn't really change anything.