I think if they had viable gas they'd be using it as gas.
They may have some sarin, but I can't help but think that if they did, and knew it, they'd be using it.
Not in a roadside artillery shell, where two people are treated for minor gas problems, but in an enclosed area. Or drop it inside the Green Zone, if they could.
Obviously, I dunno, but at this point I wouldn't get too excited about an escalation. I think they're doing all they can all the time.
Arf