A blood agent is a toxic chemical agent that affects the body by being absorbed into the blood. Blood agents are fast-acting, potentially lethal poisons that typically manifest at room temperature as volatile colorless gases with a faint odor. They are either cyanide- or arsenic-based. Exposure Blood agents work through inhalation or ingestion. As chemical weapons, blood agents are typically disseminated as aerosols and take effect through inhalation. Due to their volatility, they are more toxic in confined areas than in open areas. Cyanide compounds occur in small amounts in the natural environment and in cigarette smoke. They are also used in several industrial processes and as pesticides. Cyanides are released when synthetic fabrics or polyurethane burn, and may thus contribute to fire-related deaths. Arsine gas, formed when arsenic encounters an acid, is used as a pesticide and in the semiconductor industry; most exposures to it occur accidentally in the workplace. Symptoms The symptoms of blood agent poisoning depend on concentration and duration. Cyanide-based blood agents irritate the eyes and the respiratory tract, while arsine is nonirritating. Hydrogen cyanide has a faint, bitter, almond odor that only about half of all people can smell. Arsine has a very faint garlic odor detectable only at greater than fatal concentrations. Exposure to small amounts of cyanide has no effect. Higher concentrations cause dizziness, weakness and nausea, which cease with the exposure, but long-time exposure can cause mild symptoms followed by permanent brain damage and muscle paralysis. Moderate exposure causes stronger and longer-lasting symptoms, including headache, that can be followed by convulsions and coma. Stronger or longer exposure will also lead to convulsions and coma. Very strong exposure causes severe toxic effects within seconds, and rapid death. The blood of people killed by blood agents is bright red, because the agents inhibit the use of the oxygen in it by the body's cells. Cyanide poisoning can be detected by the presence of thiocyanate or cyanide in the blood, a smell of bitter almonds, or respiratory tract inflammations and congestions in the case of cyanogen chloride poisoning. There is no specific test for arsine poisoning, but it may leave a garlic smell on the victim's breath. Effects At sufficient concentrations, blood agents can quickly saturate the blood and cause death in a matter of minutes or seconds. They cause powerful gasping for breath, violent convulsions and a painful death that can take several minutes.