Tear gas is a broad term for chemical irritants designed to temporarily incapacitate people by causing intense burning in the eyes, skin, and airways. Despite the name, tear gas isn’t actually a gas. It’s a fine aerosol of solid chemical particles dispersed into the air, typically from canisters or grenades. The most common compounds used are CS (o-chlorobenzylidene malonitrile), CN (2-chloroacetophenone), and OC (oleoresin capsicum, the active ingredient in pepper spray).
How Tear Gas Works in the Body
All major tear gas compounds target the same pain receptor: a protein called TRPA1, found on sensory nerve endings throughout your eyes, nose, mouth, lungs, and skin. These chemicals are extremely potent activators of this receptor. When the aerosolized particles land on moist tissue, they bind to and activate TRPA1, which floods the nerve with a pain signal. The body interprets this as a chemical burn and responds with a cascade of protective reflexes: tearing, coughing, mucus production, and involuntary eye closure.
The activation is a direct chemical reaction. The compounds latch onto specific parts of the receptor, forcing the nerve channel open. This is the same receptor that fires when you bite into a raw onion or inhale wasabi fumes, but tear gas agents trigger it far more intensely. The reaction is reversible once the chemical is removed from the skin or mucous membranes, which is why decontamination speeds recovery.
Immediate Symptoms
Within seconds of exposure, your eyes begin to sting and water uncontrollably. Vision blurs. Breathing becomes difficult as the airways constrict and fill with mucus. Most people also experience a burning sensation across any exposed skin, along with coughing, choking, and a runny nose. Nausea and disorientation are common, especially in enclosed spaces where concentrations build up quickly.
At the concentrations typically used for crowd control, a dose of about 4 milligrams per cubic meter of CS will cause most people to flee within one minute. At 10 milligrams per cubic meter, even trained military personnel find it intolerable. For the vast majority of exposures, these effects resolve on their own within 15 to 30 minutes after moving to fresh air and decontaminating, though skin irritation can linger for hours.
How It’s Deployed
Tear gas canisters are the most recognizable delivery method. Inside a canister, the chemical compound is mixed with a pyrotechnic charge. When detonated, the charge heats and disperses the solid particles as a dense cloud of smoke or fog. These canisters can be thrown by hand or fired from a launcher to cover a wider area. Because the pyrotechnic reaction generates significant heat, the canisters themselves can cause burns on contact and have been known to start fires.
Pepper spray (OC) works differently. It’s stored as a liquid in a pressurized container and released as a directed stream or cone rather than a dispersed cloud. Some pepper spray formulations are also loaded into projectiles that can be thrown or launched. Handheld smoke devices offer another option, producing a slower release of irritant particles.
Long-Term Health Risks
Single, brief exposures in open air rarely cause lasting harm. But the picture changes with heavier or repeated exposure. A study of 93 people exposed to CS gas found that their risk of chronic bronchitis roughly doubled compared to unexposed individuals. Exposed subjects reported persistent cough and phlegm production at more than twice the rate of controls, and their lung function measurements showed meaningful declines, particularly among those who also smoked.
Some cases are more dramatic. In one report, a previously healthy 21-year-old woman experienced coughing, wheezing, and shortness of breath that persisted for two years after a single short-term CS exposure. In another group of 34 young adults exposed in an enclosed space, five still had respiratory symptoms and decreased exercise tolerance eight to ten months later, and two had worsening asthma.
Respiratory complaints and measurable drops in lung function can appear or persist months after the last exposure. Higher rates of runny nose, watery eyes, and skin inflammation have also been observed in exposed populations, though those differences are less statistically clear-cut than the lung effects.
Decontamination After Exposure
The single most important step is getting to fresh air. Once you’re away from the cloud, remove your outer clothing, ideally without pulling it over your face. Bag the contaminated clothes separately. If you wear contact lenses, remove and discard them, as the porous material traps chemical particles. Eyeglasses can be washed with soap and water and reused.
Rinse your eyes with plain water for 10 to 15 minutes, or until the burning subsides. Wash all exposed skin thoroughly with soap and water. Soap is important because many tear gas compounds don’t dissolve well in water alone. Avoid rubbing your skin or eyes, which can grind particles deeper into tissue. Any actual burns on the skin are treated the same way as thermal burns, with standard wound care and medicated bandages if needed.
Legal Status
Tear gas occupies a legal gray zone. The Chemical Weapons Convention, which nearly every country has signed, bans the use of riot control agents as a method of warfare. That means no military can legally use tear gas against enemy combatants in an armed conflict. The same treaty, however, explicitly permits its use by law enforcement for domestic crowd control.
The reasoning behind this distinction has less to do with the toxicity of tear gas itself and more to do with escalation. On a battlefield, a soldier hit with an unknown chemical cloud cannot tell whether it’s tear gas or a nerve agent. The fear was that tear gas use in war would provoke retaliation with far deadlier chemical weapons. Banning it from armed conflict was a way to keep that threshold from being crossed while still allowing governments to use it as a less-lethal policing tool.
How Dangerous Is Tear Gas?
Among the common agents, CN is the most toxic, followed by CS, with OC (pepper spray) considered the least toxic based on the threshold needed to cause irritation. The lethal concentration of CS in animal studies ranges from about 50,000 to 88,000 milligram-minutes per cubic meter, depending on the species. Compare that to the 4 to 10 milligrams per cubic meter used in standard crowd dispersal, and the safety margin in open-air settings is enormous.
That margin shrinks in enclosed spaces. Deaths linked to tear gas have occurred almost exclusively when it’s deployed indoors, in confined areas, or when people cannot escape the cloud. Pre-existing asthma, heart conditions, or other respiratory diseases also raise the risk of a severe reaction. Children and the elderly are more vulnerable because of their smaller lung capacity and less robust airways.