Substances that cause physical injury to the lungs. Exposure is through inhalation. In extreme cases, membranes swell and lungs become filled with liquid (pulmonary edema). Death results from lack of oxygen; hence, the victim is choked. Phosgene (CG) is a choking agent. Symptoms: irritation to eyes/nose/throat, respiratory distress, nausea and vomiting, burning of exposed skin