Tear gas is not actually a gas, but a liquid spray.
In short: Most people assume tear gas is an airborne vapor, but it is actually a solid or liquid substance dispersed into the air. Designed to overwhelm your senses without causing permanent injury, these chemicals trigger immediate physical reactions that force the body to shut down its primary defenses.
Tear gas refers to a category of substances specifically engineered to irritate mucous membranes. When exposed, they cause an intense stinging sensation in the eyes and prompt the production of tears. Beyond ocular distress, these agents target the upper respiratory tract, inducing symptoms such as coughing, choking, and general physical debility. While many people associate them with modern policing, their history dates back to chemical warfare during World War I.
Despite its name, tear gas is rarely a true gas under normal atmospheric conditions. Instead, it typically exists as synthetic organic halogen compounds in solid or liquid forms. These are converted into an aerosol by using fog generators, sprays, or grenades and shells. The two most prominent chemicals used for this purpose are $\omega$-chloroacetophenone (CN) and o-chlorobenzylidenemalononitrile (CS).
The choice between these agents depends on the desired intensity of the effect. CN is a primary component of the aerosol agent Mace and primarily targets the eyes. CS, however, is considered a stronger irritant that causes burning in the respiratory tract and forces the involuntary closing of the eyes. A key distinction is duration: while CS is more potent, its effects are shorter-lasting, often wearing off within 5 to 10 minutes of breathing fresh air.
Because these substances are designed for crowd dispersal rather than lethal force, their effects are generally temporary and reversible in most cases. Protection against these chemicals is highly effective when using gas masks equipped with activated charcoal filters. Other compounds that have been used or suggested for similar purposes include bromoacetone, benzyl bromide, ethyl bromoacetate, xylyl bromide, and $\alpha$-bromobenzyl cyanide.
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Sources
- Summary by Intellect · source: The Science of Tear Gas
- Also: Tear gas | Definition, Effects, & Facts | Britannica
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