Recall that the blend of chems planned for the attack in Jordan had some 47 or 57 different chemical toxins in it? Ugh
"atropine to fight nerve agents, for instance, or amyl nitrite for cyanide. Some are in autoinjectors for use at the site of an attack, others packaged for emergency-room use."
What did I tell ya? I think it is far more likely that if a chemical agent is employed in a terror attack it will be a single agent of the nerve toxin type rather than some form of hodge-podge recipe thrown together. Because of chemical interactions, it'd be difficult to ascertain the rate of action, persistency and means of deployment for max dispersal.
First off, nerve agents are uniformly the most deadly substance known to man. They are persistant and have a fairly even rate of action (time from moment of contamination to the moment of death). Most significantly, there is a preset means of dispersal via munitions, aerosal spray or whatever. They've been around for a very looooong time. For the properly trained individual, there's not much mystery to the use of such an agent in an attack.