Blood agent A blood agent is a toxic chemical agent that affects the body by being absorbed into the blood . They are fast - acting , potentially lethal poisons that typically manifest at room temperature as volatile colorless gases with a faint odor . Blood agents are either cyanide - or arsenic - based . Exposure . Blood agents work through inhalation or ingestion . As chemical weapon s , blood agents are typically disseminated as aerosol s 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 fabric s 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 almond s , 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 . The immediate cause of death is usually respiratory failure . Blood agents work at the cellular level by preventing the exchange of oxygen and carbon dioxide between the blood and the body ' s cells . This causes the cells to suffocate from lack of oxygen . Cyanide - based agents do so by interrupting the electron transport chain in the inner membranes of mitochondria . Arsine damages the red blood cell s which deliver oxygen throughout the body . Detection and countermeasures . Chemical detection methods , in the form of kits or testing strips , exist for hydrogen cyanide . Ordinary clothing provides some protection , but proper protective clothing and masks are recommended . Mask filters containing only charcoal are ineffective , and effective filters are quickly saturated . Due to their high volatility , cyanide agents generally need no decontamination . In enclosed areas , fire extinguishers spraying sodium carbonate can decontaminate hydrogen cyanide , but the resulting metal salts remain poisonous on contact . Liquid hydrogen cyanide can be flushed with water . Cyanide poisoning can be treated with antidotes ; see the corresponding article . List of blood agents . The information in the following table , which lists blood agents of military significance , is taken from Ledgard . The values given are on a scale from 1 to 10 . Sodium cyanide and potassium cyanide , colorless crystalline compounds similar in appearance to sugar , also act as blood agents . Carbon monoxide could technically be called a blood agent because it binds with oxygen - carrying hemoglobin in the blood ( see carbon monoxide poisoning ) , but its high volatility makes it impractical as a chemical warfare agent .