What defines materials that are dispersed in a liquid spray causing pain on mucous membranes and skin?

The definition of materials that cause pain on mucous membranes and skin when dispersed in a liquid spray aligns with irritants. These substances are specifically designed to provoke inflammation and discomfort in the body, particularly affecting the respiratory tract and skin upon exposure. Irritants can result from various chemical agents like tear gases or other compounds that, when aerosolized, can create immediate reactions in individuals, leading to symptoms such as burning sensations, coughing, and tearing.

In contrast, choking agents primarily target the respiratory system but do not directly cause pain on the skin or mucous membranes; they are more focused on causing suffocation or asphyxiation. Blood agents interfere with the body's ability to transport oxygen, and while they can be lethal, their mechanism is different from causing immediate pain as irritants do. Lastly, nerve agents affect the nervous system and can lead to debilitating symptoms, but they do not primarily act by causing irritation to mucous membranes or skin like irritants do. Understanding this classification helps in effectively identifying and responding to various hazardous materials during incidents.