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.