How many categories are used to classify chemical agents?

• A. 4
• B. 5
• C. 6
• D. 7

Answer: (C)

Chemicals are grouped by the primary effect they have on the human body, which shapes how we protect people, recognize symptoms, and respond. There are six standard categories: nerve agents that disrupt the nervous system; blister (vesicant) agents that cause severe skin and mucous membrane damage; choking (lung-damaging) agents that irritate or injure the respiratory tract; blood agents that interfere with the body's ability to use oxygen; riot control agents that are irritants used to disperse crowds; and incapacitating agents designed to prevent normal function without causing lasting harm. This six-category framework is the typical reference in training and doctrine, so six is the best answer.