Which of the following is classified as a blood agent?

Hydrogen cyanide is classified as a blood agent due to its mechanism of action and its impact on the body. Blood agents target the bloodstream and interfere with the ability of the blood to carry oxygen. When inhaled or absorbed, hydrogen cyanide readily binds to hemoglobin, inhibiting the blood's oxygen-carrying capacity and disrupting cellular respiration. This can lead to rapid asphyxiation or death, depending on the concentration and duration of exposure.

In contrast, chlorine gas is primarily a choking agent, causing irritation to the respiratory system. Mustard gas functions as a blistering agent, damaging skin and respiratory tissues rather than affecting blood directly. Phosgene, while a potent pulmonary agent harmful to the lungs, also does not primarily act on the blood like hydrogen cyanide does. Understanding these distinctions is crucial for recognizing the different types of chemical agents and their effects on human physiology.