So here's the funny thing - the first story I saw on this in Mogginn said unidentified (fair enough) sulphur gas that smelled of 'bad garlic'.
Quick, name a gas that makes a lot of people sick and smells like bad garlic? It is not mercaptan A thioether rather than a thiol. Well, can't be pure mustard gas or some of the people would have blistered and died. On the other hand, mercaptans are used as natural gas alert mixes precisely because they are not toxic. Specifically CH3SH (methyl mercaptan) which is the claimed gas in this instant. And it smells like cabbage, not garlic, a Russian should know the difference!
Did someone get a hold of old, partly degraded Mustard Gas? And was it commercial blackmail?
Not that I am paranoid or anything. Or not, not really consistent with thiodiglycol either. Weird.
But I don't believe it was just mercaptan.