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Smoke that is present during a structure fire is composed of several irritating, toxic and asphyxiant chemicals, depending on the materials that are burning. These chemicals may include hydrochloric acid, ammonia, carbon dioxide, carbon monoxide, hydrogen sulfide and hydrogen cyanide. According the U.S. Fire Administration (USFA), smoke is the killer in 60% to 80% of all fire deaths. Recent research has revealed that hydrogen cyanide present in smoke generated at building fires may play a more significant role in injuries and deaths of firefighters and civilians than once thought.
Smoke generated in structural fires from products composed of carbon and nitrogen contains various concentrations of hydrogen cyanide. Commercial products made up of materials such as wool, paper, cotton, silk and plastics may produce hydrogen cyanide when they burn. Hydrogen cyanide is formed when natural fibers, such as wool and silk, and synthetic polymers, such as polyurethane and nylon, are not completely consumed during a structure fire. These materials are used in insulation, floor coverings, and other construction materials and furnishings that may be present in a building.
The USFA estimates that approximately 20,800 residential building fires occur annually involving fuels such as mattresses, pillows and bedding materials. Synthetic components of these fuels have a tendency to burn hotter and faster than conventional materials, which results in room temperatures reaching flashover sooner. Flashover promotes the degradation of synthetics resulting in the release of hydrogen cyanide and other toxic gases.
The National Institute of Standards and Technology (NIST) investigated the fire that occurred at The Station Nightclub in West Warwick, RI, in February 2003. NIST concluded that cyanide played a key role in the 100 deaths that occurred as a result of that fire. Testing of Providence firefighters also revealed positive results for exposure to cyanide. Live-fire testing using a full-scale mockup of the nightclub demonstrated that within a few seconds of ignition of the fire, concentrations of carbon monoxide and hydrogen cyanide increased dramatically while oxygen levels in the room decreased.
Studies in other countries have produced similar conclusions. The Paris Fire Brigade studied 43 fire-related deaths and discovered a direct relationship between the blood cyanide concentration and the resulting fire death. A study in Argentina following a prison fire in which 35 inmates died produced additional evidence. Carbon monoxide levels in the victims were well within the non-lethal range, but blood cyanide levels exceeded the lethal range.
According to the Cyanide Poisoning Treatment Coalition (CPTC), exposure to hydrogen cyanide in building fires is the leading cause of cyanide poisoning. The CPTC is a non-profit organization made up of individuals and groups. Members of the coalition all have direct involvement with the identification and treatment of cyanide exposure. Their mission is, "To foster a rational approach to the diagnosis and treatment of cyanide poisoning through research, advocacy and education, thereby reducing the morbidity/mortality from cyanide-related causes." At present, there are few resources available to increase awareness of the risk of exposure to cyanide. The CPTC hopes to become an important source of information concerning cyanide poisoning and an advocate towards improvement of early recognition and appropriate treatment.
Firefighters can take actions to prevent exposure to hydrogen cyanide, which may also help to reduce some of the heart attacks that are the leading cause of firefighter deaths. One target organ of hydrogen cyanide is the heart. Most firefighters in the U.S. have access to self-contained breathing apparatus (SCBA), the primary component of personal protective equipment (PPE) to keep firefighters from being exposed to hydrogen cyanide and its effects. Firefighters should wear SCBA anytime smoke is present. Hydrogen cyanide is present not only in visible smoke, but can be present during overhaul when smoke is no longer evident - and when SCBA is often removed. That's a big mistake, as toxic gases may still be present. It's time to make operational changes that require firefighters to wear SCBA whenever smoke is present and throughout the time they are inside a structure that has been on fire, unless air monitoring concludes that the air is safe to breathe.