The physical forms of CWAs are dictated by their chemical structures and by properties such as volatility (speed of evaporation), which is inversely related to environmental persistence Nonpersistent agents are gases (such as chlorine and phosgene) or volatile liquids (such as cyanide and the G-series nerve agents) at ambient temperatures Persistent agents, which can be either solids or lowvolatility liquids, include sulfur mustard and the V- and A-series nerve agents and can pose a high risk of secondary contamination from the environment or from contaminated casualties Routes of exposure to CWAs are primarily inhalational and dermal; ocular, enteral, and parenteral (from contamination of wounds) are less common Inhalation is the typical route of exposure for volatile, nonpersistent agents, although aerosolized liquids and solids, even those of low volatility, can also be inhaled Effects following exposure may be local (at or near the sites of exposure), systemic (at body sites remote from the sites of exposure), or both Although CWAs may begin damaging tissue immediately upon exposure, with inhaled phosgene or dermal exposure to sulfur mustard, VX, or the A-series NTAs the onset of signs and symptoms may be delayed for several hours or even longer This section of the chapter focuses on the extremely potent nerve agents but will also detail other categories of toxic CWAs and several industrial chemicals General principles of supportive care for poisoned patients are detailed in Chapter 102 Toxicologic Emergencies ; these principles also apply largely to the general support of CWA victims Goals of Treatment The goals of emergency therapy are prompt recognition of chemical casualties, immediate decontamination, acute supportive care, and administration of specific antidotes and other medical countermeasures, as applicable, while protecting medical providers and hospital infrastructure from secondary contamination Clinical Considerations Clinical Recognition Chemical attacks can generate large numbers of casualties with a common exposure history, but the recognition of even isolated cases is important Perhaps the most critical emergent decision for ED staff is to distinguish cyanide from nerve-agent poisoning because the immediate antidotal therapies are quite different In both cases victims may present with sudden collapse, coma, and seizures, with many deaths occurring rapidly However, nerve-agent casualties will more likely exhibit miosis, cyanosis, copious oral and nasal secretions,