DAMASCUS, SYRIA - AUGUST 19: Members of opposition forces receive medical treatment at a field hospital after Assad regime's alleged poisonous gas attack over oppositions' frontline in the neighborhood of Jobar on the eastern outskirts of Damascus, one of the deconfliction zones in Damascus, Syria on August 19, 2017.
DAMASCUS, SYRIA - AUGUST 19: Members of opposition forces receive medical treatment at a field hospital after Assad regime's alleged poisonous gas attack over oppositions' frontline in the neighborhood of Jobar on the eastern outskirts of Damascus, one of the deconfliction zones in Damascus, Syria on August 19, 2017.
DAMASCUS, SYRIA - AUGUST 19: A member of opposition forces receives medical treatment at a field hospital after Assad regime's alleged poisonous gas attack over oppositions' frontline in the neighborhood of Jobar on the eastern outskirts of Damascus, one of the deconfliction zones in Damascus, Syria on August 19, 2017.
DAMASCUS, SYRIA - AUGUST 19: Members of opposition forces receive medical treatment at a field hospital after Assad regime's alleged poisonous gas attack over oppositions' frontline in the neighborhood of Jobar on the eastern outskirts of Damascus, one of the deconfliction zones in Damascus, Syria on August 19, 2017.
DAMASCUS, SYRIA - AUGUST 19: A member of opposition forces receives medical treatment at a field hospital after Assad regime's alleged poisonous gas attack over oppositions' frontline in the neighborhood of Jobar on the eastern outskirts of Damascus, one of the deconfliction zones in Damascus, Syria on August 19, 2017.
DAMASCUS, SYRIA - AUGUST 19: A member of opposition forces receives medical treatment at a field hospital after Assad regime's alleged poisonous gas attack over oppositions' frontline in the neighborhood of Jobar on the eastern outskirts of Damascus, one of the deconfliction zones in Damascus, Syria on August 19, 2017.