Hydrogen Cyanide (HCN) is categorized as what type of agent?

• A. Choking agent
• B. Nerve agent
• C. Blister agent
• D. Blood agent

Answer: (D)

Hydrogen cyanide is classified as a blood agent because it disrupts the body's ability to use oxygen at the cellular level. It blocks the enzyme cytochrome oxidase in mitochondria, stopping oxidative phosphorylation, so tissues become starved of usable oxygen even if blood oxygen is adequate. This systemic, rapid interference with respiration distinguishes it from other agent types: choking agents irritate or damage the lungs, nerve agents disrupt the nervous system, and blister agents injure skin and mucous membranes. Because HCN acts quickly throughout the body, exposure can lead to severe symptoms like headache, confusion, rapid breathing, and collapse, making prompt treatment crucial.