[2] Other potential routes of exposure include workplaces involved in metal polishing, certain insecticides, the medication sodium nitroprusside, and certain seeds such as those of apples and apricots.

[2] It may be suspected in a person following a house fire who has a decreased level of consciousness, low blood pressure, or high lactic acid.

At lower doses, loss of consciousness may be preceded by general weakness, dizziness, headaches, vertigo, confusion, and perceived difficulty in breathing.

At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the person progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest.

[13] Exposure to lower levels of cyanide over a long period (e.g., after use of improperly processed cassava roots; cassava is a staple food in various parts of West Africa) results in increased blood cyanide levels, which can result in weakness and a variety of symptoms, including permanent paralysis, nervous lesions,[14][15][16] hypothyroidism,[15] and miscarriages.

The last typically occurs through one of three mechanisms: As potential contributing factors, cyanide is present in: As a potential harm-reduction factor, vitamin B12, in the form of hydroxocobalamin (also spelled hydroxycobalamin), might reduce the negative effects of chronic exposure; whereas, a deficiency might worsen negative health effects following exposure to cyanide.

As such, cyanide poisoning is a form of histotoxic hypoxia, because it interferes with the ability of cells to take or use oxygen via oxidative phosphorylation.

[25]: 1475 Cyanide is a broad-spectrum poison because the reaction it inhibits is essential to aerobic metabolism; COX is found in many forms of life.

Cyanide poisoning inhibits aerobic respiration and therefore increases anaerobic glycolysis which causes a rise of lactate in the plasma.

The HSE has also questioned the usefulness of amyl nitrite due to storage/availability problems, risk of abuse, and lack of evidence of significant benefits.

Therefore, a prodrug, sulfanegen sodium (2,5-dihydroxy-1,4-dithiane-2,5-dicarboxylic acid disodium salt), which hydrolyzes into 2 molecules of 3-MP after being administered orally or parenterally, is being evaluated in animal models.

[46][47] The República Cromañón nightclub fire broke out in Buenos Aires, Argentina on 30 December 2004, killing 194 people and leaving at least 1,492 injured.

After the fire, the technical institution INTI found that the level of toxicity due to the materials and volume of the building was 225 ppm of cyanide in the air.

On 27 January 2013, a fire at the Kiss nightclub in the city of Santa Maria, in the south of Brazil, caused the poisoning of hundreds of young people by cyanide released by the combustion of soundproofing foam made with polyurethane.

Research of hydrogen cyanide by chemists Carl Wilhelm Scheele and Claude Bernard would become central to understanding the lethality of future gas chambers.

[50] In early 1942, Zyklon B, which contains hydrogen cyanide, emerged as the preferred killing tool of Nazi Germany for use in extermination camps during the Holocaust.

[51] The chemical was used to murder roughly one million people in gas chambers installed in extermination camps at Auschwitz-Birkenau, Majdanek, and elsewhere.

[60] In April 1941, the German agriculture and interior ministries designated the SS as an authorized applier of the chemical, and thus they were able to use it without any further training or governmental oversight.