Chemical weapons expert and chief operating officer of SecureBio, Hamish de Bretton-Gordon, told CBSNews.com that based on video he had seen of victims in Aleppo hospitals, the symptoms were "not really those that are identified with nerve agents or mustard gas, which are the ones most likely to be used" inside Syria.
Bretton-Gordon noted that none of the people in the hospitals treating the attack victims were wearing protective clothing. If a chemical agent had been dispersed, he said, anybody coming into contact with the victims would also be affected; "doctors treating them would be overcome."
As for the reports of a chlorine smell near the scene of the attack, Bretton-Gordon said conventional high explosives can also produce an odor which might be mistaken for chlorine, and that actual weapons using the common household chemical haven't been used since World War I. He noted that mustard gas -- which Syria is known to have stockpiled -- can produce a chlorine-like odor, but there was no indication from the images he had seen that the devastating chemical agent had been used in Aleppo on Tuesday.