Science Daily: '“The Persians will have heard the Romans tunnelling,�? says James, “and prepared a nasty surprise for them. I think the Sasanians placed braziers and bellows in their gallery, and when the Romans broke through, added the chemicals and pumped choking clouds into the Roman tunnel. The Roman assault party were unconscious in seconds, dead in minutes. Use of such smoke generators in siege-mines is actually mentioned in classical texts...�?'