This webpage from the U.S. Department of Health and Human Services Chemical Hazards Emergency Medical Management (CHEMM) provides information on choking/lung/pulmonary agents. "Choking/lung/pulmonary agents are chemicals that cause severe irritation or swelling of the respiratory tract (lining of the nose, throat, and lungs). Chemicals such as ammonia, chlorine, and phosgene cause eye, nose, and throat irritation, cough, wheezes, and dypsnea, also known as Irritant Gas Syndrome." For each of the three agents, information is provided on prehospital management as well as emergency department and hospital management.
Chemical Hazards Emergency Medical Management: http://www.chemm.nlm.nih.gov/