The agents in this class cover a wide variety of chemical structures including halogens, acyl halides, various alkylating agents, as well as metallic and nonmetallic oxides. The majority of these agents are first generation warfare agents that were evaluated and used during World War I. Research into more effective pulmonary agents continued through World War II. Various metals (e.g., cadmium, selenium) have added to the fuels of flameweapons (i.e., flamethrowers) as a means of producing high levels of toxic metal fume to augment their incendiary capabilities in situations involving soldiers occupying confined spaces such as caves and bunkers. Perfluoroisobutylene (C10-A008) is listed in Schedule 2 of the ChemicalWeaponsConvention (CWC).Chloropicrin (C10-A006) andphosgene (C10-A003) are listed in Schedule 3. Pulmonary agents are relatively easy to acquire and disperse. Pulmonary agents have been stockpiled by most countries that have pursued a chemical

weapons program, and have been used a number of times on the battlefield. Although this class of agents is considered obsolete on the modern battlefield, several of these agents are still considered a significant threat as potential improvised weapons that could be utilized in urban warfare.