How Fires Produce Cyanide



John P. Benner, NREMT-PDavid Lawrence, DO, William Brady, MD | | Friday, October 2, 2009

Every 20 seconds, a fire department responds to a fire somewhere in the U.S.(1) Whether these are "wildland" (forest or brush) or structure (house or industrial) fires, the potential for toxin production is very high.

When items burn, they release lethal chemicals, and household items -- such as carpeting, electronics, beds/mattresses and cleaning supplies -- can be particularly deadly because of the cyanide they produce during combustion. In fact, the household setting is where EMS providers will most frequently encounter cyanide.

To learn why cyanide and other toxins are released during the combustion process and why they're so harmful, we turn to some basic science concepts:

Concept #1: The process of combustion is nothing more than a basic oxidation chemical reaction. This reaction often involves adding oxygen (O2) to a substance at a certain temperature, which allows it to burn, yielding carbon dioxide (CO2) and water (H2O) as the primary products.

Concept #2: Every substance on Earth, from dirt to nylon, is made up of either organic or inorganic molecules. Organic molecules contain differing numbers of only carbon (C) and hydrogen (H) atoms. Inorganic molecules contain other elements, such as nitrogen (N), in addition to carbon and hydrogen. Many organic and inorganic substances become fuel and burn when exposed to high temperatures. When a substance (or fuel) burns (or oxidizes), the chemical make-up of the fuel is determines the products that will form.

The following figure corresponds to the basic chemical reaction for the combustion of an organic substance; the top reaction is in chemical terms and the bottom reaction is the summarized version:

CxHy + O2 = CO2 + H2O


Fuel + Oxygen = Carbon dioxide + Water + Heat

CxHy is the generic chemical formula for an organic molecule, a hydrocarbon, for instance. Using this basic formula, an example of an organic hydrocarbon would allow the X=3 and the Y=8, giving the chemical formula for propane gas, C3H8. Theoretically, if the fuel being completely oxidized, such as propane, is organic, then carbon dioxide and water will be the only products.

On the other hand, in the case of the oxidation of an inorganic molecule, other chemicals can potentially be produced. Take nitrogen (N), for example; consider the generic chemical equation for the combustion of nitrogenous compounds:

CxHyNz + O2 = CO2 + H2O + HCN


Nitrogenous Fuel + Oxygen = Carbon dioxide + Water + Cyanide

CxHyNz is a generic chemical formula of a nitrogenous compound, or one that contains nitrogen. Using this basic formula, an example of a nitrogenous compound would allow X=2, Y=3 and Z=1 to form acetonitrile, or C2H3N. Nitrogen is a typical element combined with carbon and hydrogen in many types of substances, especially natural polymers (i.e., wool and silk) and synthetic fibers (i.e., nylon and polyurethane). In addition, nitrogen is a major component of the atmospheric air that we breathe. When burned, nitrogen-containing products carry the significant potential to form between carbon, nitrogen and hydrogen directly. Depending on the numbers of each element present in the reaction or the level of completion of the combustion reaction, the product could potentially form as HCN, otherwise known as hydrogen cyanide.(2)

There's no fighting these natural processes; there are only antidotes for patients who fall victim to the dangers of combustion. To learn more about recognition and treatment of cyanide poisoning, read"Smoke Signals" from October JEMS.

John P. Benner,NREMT-P,is a practicing paramedic with the Charlottesville-Albamarle Rescue Squad, Madison County EMS, and special event medical management at the University of Virginia. He's currently attending medical school in Virginia while he remains active in EMS.

David Lawrence,DO,is a practicing emergency physician and toxicologist at the University of Virginia. He's a former EMT in various New Jersey agencies.

William Brady,MD,is a practicing emergency physician at the University of Virginia as well as operational medical director for the Charlottesville-Albamarle Rescue Squad, Madison County EMS, Seminole Trail Fire Department and special event medical management at the University of Virginia. Among other hospital duties, he also serves as the chair of the resuscitation committee at the Charlottesville-Albamarle Rescue Squad, Madison County EMS, and special event medical management at the University of Virginia.


  1. Holstege CP, Kirk MA: "Smoke Inhalation." In Goldfrank_s Toxicologic Emergencies. McGraw-Hill. Columbus, Ohio, 1749Ï57, 2006.
  2. Fortin JL, Giocanti JP, Ruttimann M, et al: "Prehospital Administration of Hydroxocobalamin for Smoke Inhalation-Associated Cyanide Poisoning: 8 Years of Experience in the Paris Fire Brigade." Clinical Toxicology. 44(1 supp 1):37Ï44, 2006.

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