Hydrogen Cyanide Recognized As Toxic Threat To Firefighters

The danger of carbon monoxide poisoning from fires is well-known. But there is another danger to firefighters and victims in structural fires that is less recognized – acute cyanide poisoning.


Firefighters think of carbon monoxide (CO) as the silent killer. More and more, however, research is pointing to hydrogen cyanide (HCN), as a second and equally hazardous threat to responders with symptoms similar to carbon monoxide poisoning.


On Feb. 20, 2003, a fire in a West Warwick, R.I., nightclub took the lives of 100 occupants after pyrotechnics were set off while the band Great White was performing. The pyrotechnics ignited substandard sound suppressing foam and created HCN and CO levels that made leaving the building difficult.


In March 2006 during a 24-hour period, one Providence, R.I., firefighter was diagnosed with cyanide poisoning after a structure fire and another who suffered a heart attack after working two different structure fires had a high HCN level in his body. In the aftermath of those three fires, 27 Providence firefighters were tested for cyanide poisoning, and eight of them were found to have elevated HCN levels.


Most firefighters can probably recall incidents during which they experienced dizziness, weakness and rapid heart rate and did not realize that they may have been exposed to cyanide poisoning. After learning from the documented experiences from the Providence Fire Department, firefighters should know that HCN is extremely toxic and has serious effects on the body.


HCN is 35 times more toxic than CO, according to researchers. It can enter the body by absorption, inhalation or ingestion, and its main targets are the heart and brain, where it degenerates the outer tissues to a point where they will never regenerate again. It often incapacitates the victim within a short period of time and has a half-life in blood of one hour.


Hydrogen Cyanide is a bi-product of combustion from ordinary materials of everyday life (insulation, carpets, clothing and synthetics). But the real offender is from combustion of man-made plastic and resins containing combinations of hydrogen, carbon and nitrogen, especially if the fire is hot and in an enclosed space.


Given that HCN is so much more toxic than CO, considerations of this deadly gas should be front and center in firefighter minds. HCN exists, and has for years, in the smoke that firefighters are exposed to everyday. Scientists are just figuring out what the long-term effects will be with repeated exposures.


Best Protection


Until research is definitive, a self-contained breathing apparatus (SCBA) is a firefighter’s best friend when it comes to protecting against HCN. Many years ago wearing an SCBA was optional, but today it is mandatory under many local, state and federal regulations. The question now is how soon should we remove the SCBA after the flames are out?


Surprisingly enough the HCN may still be present in the atmosphere in high enough concentrations to affect the firefighters. SCBA should be worn until the atmosphere is shown to be completely free of HCN using atmospheric air monitors.


The Occupational Safety and Health Administration (OSHA) Web site lists the threshold odor concentration for detection of HCN as 0.58 parts per million by the most sensitive individuals. But firefighters and others exposed to smoke from burning materials will not be able to smell the gas.


Hydrogen cyanide causes rapid death by metabolic asphyxiation. The lethal concentration in air depends upon the duration of exposure.


The American Conference of Governmental Hygienists reported that workers exposed to hydrogen cyanide concentrations ranging from 4 to 12 ppm for seven years reported increased headaches, weakness, changes in taste and smell, throat irritation, pre-cordial pain and nervous instability. Also workers exposed to low concentrations developed enlarged thyroid glands. If you have not had your thyroid gland checked, you may be experiencing underlying illnesses that you don’t realize. Get it checked regularly.


Firefighters and victims inhaling hydrogen cyanide associated with smoke, as in the burning of plastic materials, often experience cognitive dysfunction and drowsiness that can impair the ability to escape or to perform rescue operations, according to researchers. Exposure to low concentrations (or initial exposure to higher concentrations) may result in stupor, confusion, flushing, anxiety, perspiration, headache, drowsiness and tachypnea (rapid shallow breathing). Exposures to higher concentrations of HCN result in prostration, tremors, cardiac arrhythmia (which can be delayed 2 to 3 weeks post fire exposure), coma, respiratory depression, respiratory arrest and cardiovascular collapse.


Pre-Hospital Treatment


The pre-hospital treatment of acute cyanide poisoning entails removing the patient from the source of cyanide, implementing supportive modalities of 100 percent oxygen and providing cardiopulmonary resuscitation if necessary.


The typical practice of administering antidotal treatment on the basis of a presumptive diagnosis of HCN poisoning in the prehospital setting is discouraged in smoke-inhalation victims because the only antidote available in the United States are nitrates such as the Lily Kit, Taylor Kit and the Pasadena Kit. These kits can be dangerous or even fatal for a smoke inhalation victim’s concomitant carbon monoxide poisoning.


However, there is a new antidote called hydroxocobalamin, which has been effectively used in France for the past 10 years. It is designed to be used on the scene or at the hospital for acute HCN poisoning from any source. It does not have the problem of reducing the blood’s capacity to carry oxygen, as in the case of nitrate administration.


Local 799 of the International Association of Fire Fighters (IAFF) in Rhode Island recommends that departments develop and institute a training program that focuses on making members aware of the hazards of hydrogen cyanide. The union local said company officers must focus on the protection of their members while ensuring that SCBAs are used.


To comply with the National Fire Protection Association 1404 standard for respiratory protection training, firefighters should follow the Rule of Air Management (ROAM), which states that you need to know how much air is in your bottle, manage it as you go, and leave the IDLH area before your low alarm signal activates.


My analogy is that your SCBA bottle contains 4,500 psi. From 4,500 down to 1,100 psi belongs to your department for the work that you perform, and from 1,100 down to 0 psi belongs to your family.


It is very important to “consume your air,” not only during the fire attack, but also during the overhaul phase. Wearing an air pack on your back is not doing you any good unless you are consuming it until you leave the structure. The soot, vapors, and toxicants are prevalent for a long time.


Upon completion of the response, be sure to shower, change clothing, and wash your gear frequently, especially your hood, as this material is much closer to your skin than your turnouts.


Some ask, “When using an atmospheric air monitor, what is the best time to remove your SCBA?” My answer is, “Only when you are completely finished working in that environment.” The small amounts of contaminants over the career life of a firefighter will gradually affect you and lead to further complications.


I implore everyone to use their personal protection equipment to the best of their ability, use common sense and keep working toward that happy and healthy retirement.


Editor’s Note: Rick Rochford, a captain and a 26-year veteran with the Jacksonville (Fla.) Fire Rescue Department, is one of the department’s field incident safety officers. He has researched the toxic properties of HCN and CO at various structure fires and has developed training presentations for fire departments nationwide.


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