TOXICITY OF FIRE GASES
RESPIRATORY HAZARDS probably constitute the chief occupational risk to fire fighters. To substantiate this statement, the 1956 annual report of the New York Fire Department8 indicated a response to 66,435 alarms. It reported 1,383 Injuries to firemen, with smoke inhalation being by far the largest single cause of disability, constituting 287 cases.
Let us consider several examples of the poisoning of firemen through the respiratory tract. A month ago, on a Sunday morning, we had a smoky worker in a store selling second-hand clothing in Colorado Springs. Our crews were real “eager beavers.” They got inside quickly and nailed the fire before the building suffered any serious structural damage. When the fire was out and mop-up proceeding, two men complained of headache and extreme weakness on the slightest exertion. These men are well known to me, neither complains unless he is really sick. I checked them over. Their vital signs were good, but I thought they had been poisoned with carbon monoxide and perhaps other toxic products. One of them was in the hospital for 24 hours; neither was any good to the department for several days.
On Sunday morning, January 13, 1952, one of our local newspapers published a picture showing two Colorado Springs firemen sitting on a street curb. They were “sad sacks,” their faces haggard and drawn. They had been vomiting and they looked sick. They had just come out of the basement of Strang’s Garage where they had been fighting a fire. A car had struck a gasoline pump, breaking it off its base and starting a fire. The blazing gasoline had run through cracks in the floor into the basement, involving tires and accessories. Fire department response was prompt, and the fire quickly knocked down, but not before the crews operating lines in the basement had taken considerable punishment from the smoke produced by the burning tires. It probably contained carbon dioxide, carbon monoxide, sulfur dioxide and perhaps some hydrogen sulfide and cyanide. The men missed no time from duty but felt below par for several days.
On March 23, 1956, fire was discovered in the Gagnon Plating Works, just north of Colorado Springs, and two companies were dispatched. The building had been completely involved when fire was first reported, so the only fighting was done from the outside, protecting exposures and preventing extension. Burning in the open with an ample supply of air, we can be certain combustion was fairly complete, but many chemicals employed in plating were in the building and it is impossible to determine what toxic fumes were in the smoke. Even though they were outside and inhaled little smoke, two firemen ended up in the hospital complaining of extreme weakness. Examination and laboratory tests did not give a diagnosis. They recovered rapidly and were back on duty in a few days.
A plating plant is likely to stock such chemicals as sodium cyanide, potassium cyanide, silver cyanide, nitric acid, hydrochloric acid, sulfuric acid and sodium hydroxide, so there was adequate explanation for their poisoning.
A pertinent account in FIRE ENGINEERING10 told the story of a break in a large gas distribution main in an eastern city. A gas company foreman descended into a manhole to shut off the main, where he was overcome. Four men attempted to rescue him and likewise were overcome. Next, three firemen, wearing canister-type masks descended into the pit, but they, too, were overcome. The air in the manhole had been displaced by gas, thus there was insufficient oxygen in the atmosphere of the hole to sustain life, even though the masks successfully filtered out the gas. The hose from a compressor was lowered into the manhole and this flow of air enabled other firemen wearing canister-type masks to bring up the unconscious men. All were revived except the first one who had been in the pit the longest.
A classic example of mass casualties from toxic fumes occurred on May 15, 1929, at the Cleveland Clinic.2, 3, 4, 14, 25 In that building a basement coal bin had been converted into a storeroom for nitrocellulose X-ray film. Decomposition of the film is thought to have been initiated by heat from a defective steam line or from an electric light bulb. At any rate, the film decomposed, liberating vast quantities of yellow fumes, which were sucked into a pipe tunnel and delivered throughout the building via the ventilating system. The fire door on the film storage room failed to close and flames spread on woodwork up a flight of stairs to other parts of the fireproof building. A violent explosion occurred at 11:30 a.m., a time when the clinic business was at its height. Although the building was filled with dense yellow fumes, firemen and volunteers started rescue work. It was not recognized at the time, but afterwards experts concluded that decomposition of the film released nitrogen dioxide or nitrogen tetraoxide, which are highly toxic, and many were felled. Probably hall of the people in the clinic died immediately. Some of those exposed felt fine for a time, then hours later developed pulmonary edema, or accumulation of fluid in the lungs, and died. It is significant that none of the 125 who died was killed by burns.
The respiratory system of the human being is adjusted to maintain him in equilibrium when he respires a mixture containing about 21 per cent of oxygen and 78 per cent nitrogen plus traces of a few other gases.1 This mixture is called air, and at barometric pressure encountered at and not too far above sea level, is best suited for the support of animal and plant life.
Inhalation of gases other than those occurring normally in the atmosphere may cause injury or death by asphyxia or by toxic action. Such gases include carbon dioxide, carbon monoxide, sulfur dioxide, hydrogen cyanide, hydrogen sulfide, ammonia and others. Let us consider their characteristics.
Carbon dioxide is a colorless, odorless gas. It is formed by oxidation, such as the combustion of fuel. Being heavier than air, it accumulates in manholes, cellars, beer vats, wells, eaves and mines. Concentrations of 0.1 to 0.5 per cent in air may produce symptoms of headache and weakness; 8 or 9 per cent causes suffocation, and higher concentrations may be fatal. Death from carbon dioxide poisoning is probably uncommon. Fatalities which occur from imprisonment in a small room, typified by the widely publicized but rather uncommon ice box tragedies, are due as much to the insufficient oxygen supply as to the excess of carbon dioxide, while heat, humidity and the terror induced by confinement contribute to the fatal outcome.
Carbon dioxide induces asphyxia through the exclusion of oxygen, which is accelerated in the early stages by the stimulating effect of the gas on the respiratory center, producing deeper and more rapid breathing. Following this initial stimulation, collapse quickly ensues.
Carbon monoxide is a colorless gas slightly lighter than air. It is produced by incomplete combustion and in the presence of oxygen will burn or explode to produce carbon dioxide. The following explanation is essential to the understanding of the mechanism of carbon monoxide poisoning.
—Boston F. D. photo by D. E. Johnson
—Photo by Ed Heavey
Blood contains, among other things, reel blood cells floating in a fluid called plasma. These cells are red because they contain a complex iron compound called hemoglobin. The hemoglobin combines with oxygen in the lungs and carries it to all parts of the body, thereby sustaining life. The affinity, or combining power, of hemoglobin for carbon monoxide is 210 times greater than for oxygen. Therefore, if carbon monoxide is inhaled into the lungs, the hemoglobin combines with carbon monoxide in preference to oxygen, forming carboxyhemoglobin. Hemoglobin so combined is not able to carry oxygen and a fatal anoxemia, or lack of oxygen, may develop. The process is reversible. If the intake of carbon monoxide is checked before a lethal concentration is reached in the blood, and oxygen is introduced into the respired air, the hemoglobin molecule will be freed of its carbon monoxide, the latter will be eliminated during expiration, and the hemoglobin will once more carry oxygen.
Carbon monoxide does not have any known harmful effect on the red blood cells. The harm to the patient occurs from the presence of carboxyhemoglobin which prevents the hemoglobin from carrying oxygen to the tissues.1 The damage occurring is the direct result of this lack of oxygen.
Poisoning from carbon monoxide depends on the concentration of the gas and the length of the exposure. A formula has been derived from actual data by which fatal exposure to carbon monoxide may be predicted.7, 22 When the product of multiplying the time of exposure in hours by the concentration of carbon monoxide in per cent is greater than 0.15, death will probably result. The blood in most patients found dead from carbon monoxide poisoning contains over 50 per cent saturation with carboxyhemoglobin. Exposure to carbon monoxide in low concentrations for a considerable length of time, such as during sleep, poisons the victim just as effectively as high concentrations for a short period of time. It is said that two deep breaths of 2-per-cent carbon monoxide may cause unconsciousness and death in four and a half minutes. In the face of this information, consider that motor car exhaust contains about 7 per cent carbon monoxide.
Diflerences in susceptibility to asphyxiation by carbon monoxide depend on the patient’s resistance, on the amount of hemoglobin in the blood (low in anemia), on depth and rapidity of breathing in relation to body weight, and on the conditions of exposure.” Acute poisoning by carbon monoxide produces headache at first, then weakness and a rapid forceful heart beat, which is quickly followed by a feeble pulse, labored respiration, extreme weakness and coma. The cherry red color of carboxyhemoglobin may give the patient a characteristic coloring.
In some cases of carbon monoxide poisoning, the victim may be rescued while in deep coma. He may be revived and have no aftereffects. Other cases recover slowly and have distressing sequelae, such as permanent damage to the brain or the heart or other organs from prolonged oxygen lack.
Due to the strong affinity of hemoglobin for carbon monoxide, sometimes a victim of this poisoning, with 50 per cent of his hemoglobin combined with carbon monoxide, may regain consciousness while at rest, only to collapse or become unconscious if he attempts to walk. Exertion rapidly depletes the oxygen content of the remainder of the hemoglobin.
This discussion of carbon monoxide poisoning is intentionally lengthy, since it is encountered at almost every fire. Carbon monoxide is colorless, odorless and tasteless, and aside from early headache, its effects may be insidious, yet it is very poisonous. It probably causes more fire deaths than any other factor, including burns.
Sulfur dioxide is a colorless gas heavier than air and so pungent that it just cannot be breathed. Inhalation produces sneezing, coughing, irritation of the lung passages, spasm of the glottis, and death from rapid suffocation.
The oxides of nitrogen causing the yellow or brown smoke described in the fire at the Cleveland Clinic, came from the combustion of nitrocellulose photographic film. This source should not be a problem, since most film recently used is cellulose acetate or safety film. Nitric fume poisoning may come from a fire involving a nitric acid plant, smokeless powder, or pyroxylin plastic. Firemen have died as a result of breathing these orange-brown fumes for only a few minutes.18 Inhalation of the oxides of nitrogen anesthetize the throat so no discomfort is felt immediately, but it may cause massive pulmonary edema in the lungs, which may develop hours after exposure and cause death. Men with minimal exposure to the nitrogen oxides should be kept in bed several days to limit the lung injury.
Carbon tetrachloride has uses in industry and as a fire extinguishing agent. Its toxicity is sufficient that it deserves mention.1 If swallowed, it may produce acute poisoning with inebriation, headache, nausea, vomiting, diarrhea, eonvultions, and death from failure of circulation or respiration. Inhalation of fumes may cause irritation of the air passages. If death does not occur, late manifestations of carbon tetrachloride poisoning may be in damage to the liver, kidneys or heart muscle. Enclosed spaces must be ventilated, following fires extinguished with carbon tetrachloride, to clear the air of fire gases and the extinguishing vapor and the products of its decomposition. When carbon tetrachloride comes in contact with flame, it may produce toxic gases, the most important of which is probably hydrochloric acid.25,26 Many products of combustion cause such irritation to the membranes of the nose and throat that spasm of the bronchioles or coughing keeps these irritants from ever reaching the lungs, thus protecting the lungs from damage. This is not the case with the oxides of nitrogen mentioned above, which anesthetize the throat so that no initial discomfort is felt, nor is it the case with hydrochloric acid from breakdown of carbon tetrachloride, which gets to the lungs and causes pulmonary edema.
—Philadelphia F. D. photo by Kennedy
Cyanide is a gas which deserves mention because of its very high degree of toxicity. Hydrocyanic acid is a liquid which boils at about 80° F. It is a highly effective fumigant, diffuses rapidly, and kills all living organisms. It is produced in the combustion of certain substances including photographic film decomposing in the absence of oxygen, from silk, wool, and some plastics. Hydrocyanic acid gas is so toxic that very small amounts will kill in a very short time.1 Some may be absorbed directly through the skin.
Hydrogen sulfide, the gas with an odor like rotten eggs, is quite poisonous. It is considered four times as poisonous as carbon monoxide and somewhat similar to cyanides in toxicity.7, 17 Firemen may encounter it in a chemical laboratory, certain manufacturing plants, or perhaps during a rescue from a sewer or cesspool.1 Inhalation may cause paralysis of the central nervous system and death. Again, treatment is by artificial respiration and oxygen. If the patient survives, he will probably have no permanent aftereffect.
The first symptom of poisoning by either carbon monoxide or hydrogen sulfide is the onset of headache. This should not be ignored, for it is a danger signal.
We have spoken of several examples of substances which may cause serious disability or death if they are in the air we breathe. Do these concern the men of the fire service? The answer is, they most certainly do, for they arc common constituents of what a fireman is supposed to eat, namely, smoke.
Following the fire in the Cleveland Clinic, extensive studies were done on the products of combustion of nitrocellulose photographic film, and also of the cellulose acetate, or safety film which has pretty well replaced it. Decomposing in the absence of oxygen, these films produce carbon dioxide, carbon monoxide, hydrogen cyanide, acetic acid, and the nitrocellulose film produces oxides of nitrogen. Burning in the presence of adequate oxygen, the products are chiefly carbon monoxide and carbon dioxide. You will recognize in this list several of the toxic gases described above.
For samples of the products of combustion of various substances, start with wood, which is the chief fuel in manystructural fires. Burning without adequate oxygen, the products of its combustion include carbon monoxide, formaldehyde, formic acid, carbolic acid, methyl alcohol, acetic acid and other compounds. If the oxygen supply is poor, smoke will be dense and contain many organic irritants. If the oxygen supply is good, the irritants burn and the smoke then contains carbon dioxide, carbon monoxide, and only a small amount of organic compounds.
Plastics, which make up so many useful and attractive items in this Twentieth Century, burn to carbon monoxide, hydrochloric acid, cyanide, oxides of nitrogen, and other toxic compounds.
Burning rubber produces a smoke with a disagreeable odor. Many firemen remember the headache that lasted 24 or 48 hours after they had attacked a rubber fire. The smoke from the burning rubber contains carbon monoxide, hydrogen sulfide, sulfur dioxide and other compounds.
Burning silk is extremely dangerous due to the high content of hydrogen cyanide and ammonia in the smoke. As silk has been replaced by nylon, one hazard has been eliminated, but fumes from burning nylon aren’t innocuous either.
Burning wool produces smoke containing carbon monoxide, hydrogen sulfide, sulfur dioxide and considerable hydrogen cyanide.
In an actual fire the smoke is a mixture of various gases, and the evidence indicates that the toxicity is greater than the sum of the toxicity of the components of the mixture. Deficiency of oxygen and high temperature further increase toxicity and the hazard to firemen.
From the foregoing information, it is evident that smoke is toxic. It would be easy to conclude here that since smoke is toxic, firemen should avoid it. If such a policy were followed, fire losses would rise. Fires can’t be stopped early by hose lines directed from the street through windows and doors. Fast stops can only be made by getting inside and applying extinguishing agents to the seat of the fire. Can a compromise be achieved? What can be done to help the fireman come to close grips with the fire and yet avoid smoke poisoning?
Early ventilation is essential, since it allows smoke and fumes to be exhausted and replaced by fresh air, thus providing an atmosphere that can be tolerated.
Dr. William Claudy, surgeon of the Washington, D. C., Fire Department, in his book “Respiratory Hazards of the Fire Service,” sagely notes that a fire burning in conditions conducive to high concentrations of carbon monoxide in the smoke will likely be a fire burning in a tightly enclosed space, often below grade, and that here the situation is ripe for a smoke explosion or back draft. Such a fire must be ventilated before entry can be made safely, and always ventilate from the top first. I was blown out of a building once in a smoke explosion, and it was a very unpleasant experience. Adequate ventilation reduces the chance of a smoke explosion, eliminates carbon monoxide and other toxic gases, and allows men to advance lines and come to close grips with the fire. Fog streams can be used to absorb toxic or irritant gases.
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The smoke from most class A fires is black or gray and contains highly irritating particulate matter. This is sufficiently irritating so as not likely to be drawn deep into the lungs, nor is it likely to be tolerated for too long a time. Thus, even though such smoke contains carbon monoxide and perhaps small amounts of cyanide and sulfur dioxide, enough isn’t likely to be inhaled to kill a fireman. He’ll generally get outside first. He may be sick from it, but he probably won’t die unless trapped and forced to inhale the smoke. I would recommend that firemen avoid the brown or yellow smoke, since it is apt to contain the highly toxic oxides of nitrogen.
Experienced smoke-eaters have learned some tricks that enable them to tolerate smoky atmospheres for a considerable time. They warn the rookie not to enter a bushy atmosphere when he is short of breath from exertion. Get a big lungfull of air before entering; it can be made to last quite a time, perhaps long enough to open windows or make a rescue. Generally there is some air close to the floor, so stay low, or keep close to the nozzle where there may be some air to breathe.
Respiratory protective equipment
The subject of respiratory protective equipment has purposely been left to the last, because it is the only real answer to the entire problem presented by a fireman’s exposure to toxic gases. The very nature of his calling means that the fireman will be exposed to smoke. In a fire, density of smoke is not an indication of its toxicity. Some powerful toxic agents are odorless and colorless. Yellow or brown smoke will probably be highly toxic, but gray and black smoke may be toxic, too. There is no safety in any kind of smoke.
If there is sufficient oxygen in the air, the all-service mask gives protection. Often oxygen is lacking since it has been used up in the fire, and in such a situation, the self-contained mask is essential. Only a mask with its own supply of air or oxygen assures the fireman protection from oxygen lack or the presence of toxic gases.
The fireman who wears a mask isn’t a sissy. He is a smart fireman and is likely to remain a live one. There is no doubt wearing a mask slows up a man, but it is a lot better that he be able to do some work than not be able to work at all.
One fundamental rule of fire fighting should be that no one, unless equipped with oxygen or air-supplying apparatus, be allowed into a fire-involved basement where flame is not visible.
Following exposure to any of the toxic gases, first-aid treatment should consist of removal of the patient to safety and the administration of oxygen. If the patient is not breathing, give artificial respiration immediately or use the resuscitator. Do not give Carbogen unless advised to do so by a physician. While the carbon dioxide it contains is a respiratory stimulant, the patient has probably had more than a stimulating dose already. Treat shock in the usual way. Do not douse the victim with cold water, slap his face or feet, or attempt to talk to him since these increase the burden on the lungs and heart and may precipitate or deepen shock. To ease the work load required of the lungs, allow no exertion. Transport the patient on a stretcher. Keep him flat, do not let him up. Do not give liquid stimulants to an unconscious patient, for they may go down the trachea instead of the esophagus and add to the respiratory difficulties. Call a physician and when he is called, inform him what condition he will be expected to treat. As with the fire chief, the doctor’s size-up begins when he rolls in response to the emergency. If hospitalization is necessary, radio ahead, so that the hospital attendants may be mobilized and informed what to expect. Be sure oxygen is administered as well as artificial respiration, if necessary, while the patient is being transported in the ambulance.
An important consideration in planning treatment of any victim of poisoning, inhaled or otherwise, is the determination of the causative agent. When the principal ingredients of smoke are known, specific treatment may be planned. If a fire involves an industrial plant, and firemen are overcome, it may be possible to learn from the plant manager what chemicals are in the building.
Poison information centers
Most large cities maintain a poison information center. Such a center is established in Denver to serve the Rocky Mountain area, and information is available within minutes through a long distance telephone call as to the toxicity of various compounds and the treatment indicated. Such information on the toxic agent, when passed along to the doctor or hospital, helps in planning specific treatment for casualties.
When a fireman exposed to smoke has been overcome, or made ill by it, then is brought outside, and seems to recover, it would be unwise to permit him to return to the smoky atmosphere immediately. While he may have recovered enough to seem normal in pure air, he probably still has considerable carbon monoxide in his bloodstream, and with a second exposure he would probably succumb much quicker than the first time. At this stage, his judgment is probably impaired; he may be belligerent and insist on going back in. Don’t let him! It would be much better to keep that man outside. He’ll be ready for a smoky one on the next shift.
- Legal Medicine, Pathology and Toxicology, by Gonzales, Vance, Halpcra & Umberger, 2nd Edition, published by Appleton-Century-Crofts, Inc., New York, 1954.
- FIRE ENGINEERING, May 29, 1929, page 445-446, for account of Cleveland Clinic Fire.
- 1929 Fire Prevention Year Book, page 10, for account of Cleveland Clinic Fire.
- Going to Blazes, by Robert V. Masters, published by Sterling Publishing Co., New York, 1950, page 37, for account of Cleveland Clinic Fire.
- Handbook of Poisons, by R. H. Dreisbach, Lange Medical Publications, Los Altos, Calif., 1955.
- Occupational Hazards of the Fire Service, by C. W. Irwin, M.D., printed in “Fireman” for June, July and August, 1953, NFPA.
- The Respiratory Hazards of Fire Fighting, by E. Mastromatteo, M.D., Oct. 1953, reprinted by Scott Aviation Corp.
- New York Fire Dept. Annual Report Statistics for 1956, published in WNYF for October 1957, page 14.
- Special Interest Bulletins, NBFU, Numbers 11, 12, 49, 65, 97, 98, 99, 225, 252, 278, 282, 283.
- FIRE ENGINEERING, January 1958, page 39.
- List of Respiratory Protective Devices Approved by the Bureau of Mines, by S. J. Pearce and L. B. Berger, published by U. S. Dept, of Interior, June 1952.
- Mine Cases and Methods for Detecting Them, by J. J. Forbes and G. W. Grove, published by Bureau of Mines, 1954.
- Protection Against Mine Gases. Protection Against Mine Gases, by J. J. Forbes and G. W. Grove, published by Bureau of Mines, 1954.
- Clinical Memoranda on Economic Poisons. Protection Against Mine Gases, U. S. Dept, of Health, Education and Welfare, 1956.
- Gas Masks for the Fire Service. Protection Against Mine Gases, by Chief Harold J. Burke, NYFD, published by IAFC, 1947.
- Hospital Fire Safety Protection Against Mine Gases, NFPA, 1951, page 44.
- Handbook of Fire Protection, Crosby-Fiske-Forster, NFPA.
- Fire Protection for Chemicals, by Charles W. Bahme, NFPA, 1956.
- Respiratory Hazards of the Fire Service, by William D. Claudy, M.D., NFPA, 1958.
- Sources and Dangers of Carbon Monoxide Gas (Heating and Cooking Equipment), by Joseph L. Antonio and P. W. Jacoe, Denver.
- You Bet Your Life, by R. V. Fitzpatrick, MSA, from Proceedings, FDIC, 1951.
- Fire Gas Research Report, NFPA Quarterly, Vol. 45, No. 3, January 1952.
- Fires in Hospitals and Institutions, NFPA, reprinted from NFPA Quarterly, October 1945, page 12.
- Textbook of Medicine, Cecil.
- Structural Fire Fighting Manual, U. S. Navy, 1953, OPNAV Instruction 55607, page 22.
- FIRE ENGINEERING, February 1958, page 144, Questions and Answers, “Carbon Tet Decomposition.”
- FIRE ENGINEERING, January 1959, page 42.