Tear gas was used in combat by Italy in the Second Italo-Ethiopian War, by Japan in the Second Sino-Japanese War, by Spain in the Rif War and by the United States in the Vietnam War, and the Israel–Palestine conflict. Tear gas exposure is an element of military training programs, typically as a means of improving trainees' tolerance to tear gas and encouraging confidence in the ability of their issued protective equipment to prevent chemical weapons exposure. Riot control Certain lachrymatory agents, most notably tear gas, are often used by police to force compliance. In some countries (e.g., Finland, Australia, and United States), another common substance is mace. The self-defense weapon form of mace is based on pepper spray which comes in small spray cans. Versions including CS are manufactured for police use. Xylyl bromide, CN and CS are the oldest of these agents. CS is the most widely used. CN has the most recorded toxicity. Typical manufacturer warnings on tear gas cartridges state "Danger: Do not fire directly at person(s). Severe injury or death may result." Tear gas guns do not have a manual setting to adjust 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 targets, causing risk for non-targets instead. Counter-measures A variety of protective equipment may be used, including gas masks and respirators. In riot control situations, protesters sometimes use equipment (aside from simple rags or clothing over the mouth) such as swimming goggles and adapted water bottles, as well as covering as much skin as possible. Activists in United States, the Czech Republic, Venezuela and Turkey have reported using antacid solutions such as Maalox diluted with water to repel effects of tear gas attacks, with Venezuelan chemist Mónica Kräuter recommending the usage of diluted antacids as well as baking soda. There have also been reports of these antacids being helpful for tear gas, and for capsaicin-induced skin pain. During the 2019 Hong Kong protests, frontline protesters became adept at extinguishing tear gas: they formed special teams that spring into action as soon as it is fired. These individuals generally wear protective clothing, including heat-proof gloves, or cover their arms and legs with cling film to prevent the painful skin irritation. Canisters are sometimes picked up and lobbed back at police or extinguished straight away