Tear gas Tear gas , formally known as a lachrymatory agent or lachrymator ( from " lacrima " meaning " tear " in Latin ) , is a non - lethal chemical weapon that stimulates the corneal nerves in the eye s to cause tears , pain , and even blindness . Common lachrymators include pepper spray ( OC gas ) , CS gas , CR gas , CN gas ( phenacyl chloride ) , nonivamide , bromoacetone , xylyl bromide , syn - propanethial - S - oxide ( from onions ) , and Mace ( a branded mixture ) . Lachrymatory agents are commonly used for riot control . Their use as chemical warfare agents is prohibited by various international treaties . During World War I , more toxic lachrymatory agents were used . Effects . Tear gas works by irritating mucous membranes in the eyes , nose , mouth and lungs , and causes crying , sneezing , coughing , difficulty breathing , pain in the eyes , temporary blindness , etc . With CS gas , symptoms of irritation usually appear after 20 – 60 seconds of exposure and commonly resolve within 30 minutes of leaving ( or being removed from ) the area . With pepper spray ( OC gas ) , the onset of symptoms , including loss of motor control , is almost immediate , forcing the victim to abandon aggressive behavior in 90 % of cases . Lachrymators are thought to act by attacking sulfhydryl functional groups in enzyme s . One of the most probable protein targets is the TRPA1 ion channel that is expressed in sensory nerves ( trigeminal nerve ) of the eyes , nose and mouth . Risks . As with all non - lethal , or less - than - lethal weapons , there is some risk of serious permanent injury or death when tear gas is used . This includes risks from being hit by tear gas cartridges , which include severe bruising , loss of eyes , skull fracture , and even death . While the medical consequences of the gases themselves are typically limited to minor skin inflammation , delayed complications are also possible : people with pre - existing respiratory conditions such as asthma , who are particularly at risk , may sometimes require hospitalization or even ventilation support . Skin exposure to CS may cause chemical burn s or induce allergic contact dermatitis . When people are hit at close range or are severely exposed , eye injuries involving scarring of the cornea can lead to a permanent loss in visual acuity . Use . Use in war . Use of tear gas in warfare ( as all other chemical weapon s ) is prohibited by various international treaties that most states have signed . Police and private self - defense use is not banned in the same manner . Armed forces can legally use tear gas for drills ( practicing with gas masks ) and for riot control . First used in 1914 , xylyl bromide was a popular tearing agent since it was easily brewed . The US Chemical Warfare Service developed tear gas grenades for use in riot control in 1919 . Use in riot control . Certain lachrymatory agents are often used by police to force compliance , most notably tear gas . In some countries ( e . g . , Finland , Australia , and the United States ) , another common substance is mace , which is the same as CN and is used as a self - defense weapon , in small spray cans . Xylyl bromide , CN and CS are the oldest of these agents , and CS is the most widely used . Typical manufacturer warnings on tear gas cartridges state " Danger : Do not fire directly at person ( s ) . Severe injury or death may result . " Such warnings are not necessarily respected , and in some countries , disrespecting these warnings is routine . In the 2013 protests in Turkey , there were hundreds of injuries among protesters targeted with tear gas projectiles . However , tear gas guns do not have a manual setting to increase or decrease the range of fire . The only way to adjust the projectile ' s range is to aim towards the ground at the correct angle . Incorrect aim will send the capsules away from the protesters , causing risk for ordinary citizens instead . For example , this occurred during the 2013 protests in Brazil . Counter - measures . The most obvious counter - measure is to prevent contact with the gas by leaving the area . Alternatively , a variety of protective equipment may be used , including gas mask s and respirator s . In riot control situations , protesters sometimes use a wide variety of equipment ( aside from simple rags or clothing over the mouth ) such as swimming goggles and adapted water bottles . Treatment . Once a person has been exposed , a variety of treatments may be used . The standard first aid for burning solutions in the eye is irrigation ( spraying or flushing out ) with water , and some evidence suggests that diphoterine solution , a first aid product for chemical sprays , may help with ocular burns or chemicals in the eye . Home remedies . Activists in the United States , the Czech Republic , and Turkey have reported using antacid solutions such as Maalox diluted with water as a home remedy for tear gas attacks . Vinegar , vaseline , milk and lemon juice solutions have also been used by activists . It is unclear how effective these remedies are . In particular , vinegar itself can burn the eyes and prolonged inhalation can also irritate the airways .