Arsine (SA)
Arsine, also called Arthur, is a gas with a mild, garlic-like odor. Often used as a delayed-action casualty agent, arsine interferes with the functioning of the blood and damages the liver and kidneys. Slight exposure results in headaches and uneasiness. Increased exposure causes chills, nausea and vomiting. Severe exposure damages the blood and causes anemia. A dose of 5,000mg·min/m3 is lethal to 50 percent of exposed adults. It is estimated that 2 milligrams of SA per kilogram of body weight would be lethal to humans. Arsine was studied extensively during World War I, but because of its high volatility and chemical instability, weaponization of arsine was abandoned. Arsine is used today for industrial processing of gallium arsenide chips in the semiconductor industry.    

Cyanogen Chloride (CK)
Cyanogen chloride is a colorless, highly volatile liquid with a pungent, biting odor. The odor is usually unnoticed because the agent causes instant irritation to the mucous membranes and tearing to the eyes. Although cyanogen chloride quickly evaporates, vapors may persist in forest or jungle environments for quite some time under suitable weather conditions. Cyanogen chloride irritates the respiratory tract in a manner similar to phosgene, but fluid will accumulate in the lungs much faster than in phosgene poisoning. A dose of 11,000mg·min/m3 is lethal to 50 percent of exposed individuals. While the process of interfering with use of oxygen by body tissues is similar to that of hydrogen cyanide, cyanogen cyanide has strong irritating and choking effects and slows breathing. High concentrations of cyanogen chloride could degrade the effectiveness of a mask.   

Hydrogen Cyanide (AC)
Hydrogen Cyanide can be readily synthesized in large quantities and is commercially available. Also known to the Germans as Zyklon B, hydrogen cyanide was used by the Nazis in World War II for mass executions of Jews and other prisoners. The Soviet Union perfected the use of hydrogen cyanide, including munitions and spray tanks for low altitude dissemination. Japan also investigated the use of hydrogen cyanide, but the agent was never to become a staple of its chemical arsenal. There were reports that the Japanese army employed hydrogen cyanide against during attacks on China. The United States issued cyanide pills (L pills) to its intelligence agents during World War II to be ingested in the event of capture. Unfortunately, when taken in pill form, hydrogen cyanide produces painful death-throes, which may last for several minutes. Use of hydrogen cyanide in modern battlefield situations is unsubstantiated, but reports in the 1980s suggest that hydrogen cyanide was used by the Syrian government against an uprising in Hama, Syria, in an Iraqi military attack on the Kurdish town of Halabja, Iraq, in 1988, and in Shahabad, Iran, during the Iran-Iraq War. Hydrogen cyanide has a faint bitter almond or peach kernel odor and is a colorless liquid. It is often undetectable even in lethal concentrations. A lethal dose of hydrogen cyanide varies widely with concentration. At 200mg/m3, 2,000mg·min/m3 is lethal to 50 percent of exposed adults, whereas at 150m/m3, 4,500mg·min/m3 is lethal to 50 percent of individuals exposed. Hydrogen cyanide is a rapid-acting agent. Incapacitation can occur within one to two minutes of exposure, depending upon the concentration of the dose. Death can occur within 15 minutes after exposure to a lethal dose. Hydrogen cyanide is very unstable in storage unless in its pure form. After extended periods in storage, hydrogen cyanide forms an explosive polymer.