I don't think Erdog has the cajones to take on Assad's chem/bio. This is the reason Iran's possession of a nuke is so distressing. Once protected by the bomb they will be able to make mischief in any way they choose.
Turkey has a well trained and powerful military but it is insufficient to stop a barrage of chem/bio scuds.
I'm surprised Assad didn't use them against the rebels. But he knows that the Turkish will be pissed at anything done near or within their territory.