Pathophysiology of Pulmonary Chemical-Warfare Injuries Toxic chemical-warfare agents that affect the respiratory tract are divided into 2 types depending on which part of the tract is predominantly affected (see table Representative Type 1, Type 2, and Mixed-Effect Chemicals With Acute Local Effects on the Respiratory Tract): Type 1 agents: Affect large airways Type 2 agents: Affect terminal and respiratory bronchioles, alveolar sacs, and alveoli Mixed-effect agents: Affect large airways and small airways and alveoli Type 1 agents usually are those with inhaled particles (eg, smoke), which tend to settle out before reaching the alveoli, or highly water-soluble and / or highly reactive chemicals, which dissolve into respiratory mucosa before reaching the alveoli.