What Smoke Can Do to Your Body

What Smoke Can Do to Your Body

Part 2: Hyperventilation, heat exhaustion and heart attacks

Continued from August Issue

From the preceding discussion, it is obvious that the atmosphere a fire fighter breathes may be harmful to him in a variety of ways. To prevent injuries of this type, fire fighters have adopted the use of respiratory protective devices, but these devices may fail to give protection against a hazardous atmosphere for a number of reasons. In fact, the design of some of this equipment is such that it may produce respiratory problems which would not be present without the equipment! The use of respiratory protective equipment must not lull the wearer into a false sense of security.

Filter masks

The use of a respiratory protective device may still leave the wearer liable to injury both from hypoxia and exposure to toxic gases. Filter cannister type masks may allow the wearer to become hypoxic if they are used in an oxygen-deficient atmosphere, if the cannister resistance is too high to allow a sufficient volume of air to enter, or if the carbon monoxide absorbent is exhausted or incapable of handling a higher than usual carbon monoxide concentration. Hypoxia may occur with users of self-contained breathing apparatus if the valves are faulty, the facepiece leaks or the cylinder becomes empty.

Breathing apparatus will not prevent exposure to toxic gases if the cannister is the wrong one for the gas encountered, if the concentration of gas exceeds the maximum which can be absorbed, if the equipment leaks or if the air tanks are charged with impure air.

Self-contained breathing apparatus offers the best all-round respiratory protection available to the fire fighter at this time because it protects him against all concentrations of all types of toxic gases and smoke in addition to providing an oxygen supply. The cannister mask is quicker, lighter, and less bulky, but it offers no oxygen supply and affords protection only against some gases in certain concentrations. In today’s world of plastics, chemicals and synthetic building materials and textiles, the fire fighter should not be content with a respiratory protective device which affords only the limited protection of a cannister mask.

Learn to spot symptoms

However, no device is of value, if it is not used or if it is removed before ventilation of the structure is complete. The tendency to use breathing apparatus only when dense visible smoke is present is dangerous, for lethal concentration of carbon monoxide or other gases may be present when there is little or no visible smoke. Once a device is put to use, the wearer must realize that it is not perfect, and he can still be exposed to the hazards of oxygen-lack and toxic gases. He and his officers should be taught to recognize the early symptoms of these conditions and take appropriate action. Too often, early symptoms of difficulty are ignored until an advanced stage is reached because everyone believes the man using some type of mask is protected against all respiratory hazards.

All situations I have discussed so far threaten a fire fighter’s health either by injuring the respiratory system directly or by gaining access to some other part of the body by means of the respiratory system. Fire fighters are also subject to another group of disorders or conditions which frequently masquerade as, or are confused with, respiratory problems.

The confusion arises because these disorders appear acutely in men working in the heat, smoke and tension of the fireground, and they produce the symptoms of collapse and labored or difficult breathing so often seen in patients with respiratory problems. These disorders, however, are not the direct result of exposure of the respiratory system to smoke or gases.


The first of these disorders has the medical name of hyperventilation syndrome, or simply, breathing too much. To understand this condition, we must remember that breathing not only brings oxygen into the body but also removes carbon dioxide from the body. The removal of carbon dioxide is never complete, and normally a certain amount of this gas is present in the bloodstream, where it serves the important function of regulating the acid-base balance of the body.

By breathing too deeply or too rapidly, or both, the victim of hyperventilation syndrome exhales too much carbon dioxide from the body, and this causes the blood to become less acid and more alkaline, resulting in disordered body functions. Especially affected are the functions of the nervous system. At first, numbness of the hands, feet and face occur, but as excessive breathing continues, there may be twitching of the muscles, loss of consciousness and even convulsions.

Effect of heat

Hyperventilation syndrome in fire fighters may be the result of fear and anxiety alone, and individuals who respond in this way to the stresses and tensions of the fireground are simply unsuited to be fire fighters. Men exposed to high temperatures tend to overbreathe or hyperventilate as the body attempts to eliminate heat by means of the respiratory tract, much as a dog pants on a hot day.

In my experience, hyperventilation in fire fighters is most commonly a delayed reaction following smoke exposure. These men apparently hold their breath or reduce their breathing during exposure in an effort to avoid breathing the smoke. Since a period of overbreathing normally follows an episode of breath holding, these men collapse from hyperventilation after they emerge into fresh air.

Hyperventilating individuals should not be given oxygen from a resuscitator, since this will only increase their breathing. They will recover quickly, however, if made to rebreathe their own exhaled air from an ordinary paper sack or rubber breathing bag, since this procedure will restore the carbon dioxide content of their blood to normal.

Heat exhaustion

Another cause of collapse and difficult breathing may be confused with a true respiratory problem is heat exhaustion. These men lose enough water through perspiration to faint due to reduced blood volume, the condition commonly called shock. As has been mentioned, hyperventilation accompanies heat exposure and contributes to the patient’s difficulties.

The diagnosis and treatment of heat exhaustion can be difficult for the physician, but most of these cases are preventable if men working under conditions of high temperature will drink adequate quantities of water and learn to pace their activities so that they don’t attempt to do too much at once.

Heat is capable of damaging the respiratory system directly, but such injuries are rare in fire fighters. The respiratory tract can be burned by the inhalation of steam but not by the inhalation of dry, hot air or even flames because of the low specific heat of dry gases. Steam burns of the lungs resemble chemical burns of the lungs produced by pulmonary irritant gases but are much less common. In fact, I have never seen a steam burn of the lungs of a fire fighter, although I have seen them in fire victims. The possibility of producing steam bums of the lungs of trapped persons should be considered when using fog to extinguish interior fires because this procedure produces large amounts of steam.

Heart attack

The last condition which may masquerade as a respiratory problem or injury in a fire fighter is a heart attack. The collapse, chest pain and difficulty in breathing produced by an acute coronary occlusion can be easily confused with the symptoms of respiratory disorder, and the conditions of tension, heat, smoke and the necessity of heavy physical work which brings on heart attacks are the same ones which result in respiratory casualties. It may be genuinely difficult to tell the imposter from the real disease in some cases so that it is a good idea to have an electrocardiogram made on fire fighters who collapse on the fireground, especially if they are over 40 years of age or are known to have conditions which predispose to heart attacks, such as obesity or high blood pressure.

With so many respiratory and related disorders to confront us, what can be done to prevent fire fighters from sustaining this type of injury? I believe that now, today, we should provide every man with self-contained breathing apparatus and train him to use it properly. Once the equipment is available, it should be used regularly. The man who does not use the equipment should be looked upon as a fool rather than a hero who can “really get in there and take a beating.” The fire fighter today is exposed to an increasing number of toxic gases which make the “hero” approach too dangerous.

I believe that we should have closer cooperation between the medical profession and the fire fighter so that the knowledge now available about the causes of respiratory disorders and the methods of preventing and treating them can be more generally applied.

For the future, we should encourage research in several areas. Medicallyoriented research needs to be done on the composition of fire smoke and gas, the nature of the toxic agents present and their effects on human beings following both acute and chronic exposure. New and improved methods of treating exposed persons should be developed. The results of this research should be made available to physicians through their regular channels of information, such as medical journals and textbooks. At the present time, the medical literature contains almost nothing on these subjects, even though the technical literature of the fire service contains some excellent information.

There is also a need for medical and engineering research with a view toward developing self-contained breathing apparatus that is lighter and less bulky. If possible, this apparatus should be built into the fire fighter’s helmet and clothing so that it is constantly available.

I have presented a long and rather complicated list of respiratory problems and related conditions which may affect fire fighters. The important thing is that we cannot be content to label every man who collapses on the fireground as being “overcome by smoke.” Those of us who are responsible for the health of fire fighters must look beyond the smoke for the true causes of respiratory and related disorders so that we will be better able to prevent and treat this type of injury.

What Smoke Can Do to Your Body


What Smoke Can Do to Your Body

Adapted from an address delivered at the IAFC Conference at Louisville.

The occupation of fire fighter exposes a man to many hazards. Among the most common of these are the problems that arise from exposure of the respiratory system, and through the respiratory system the entire body, to smoke and toxic gases.

Every man who becomes unconscious or has obvious difficulty in breathing is not necessarily a smoke casualty. He may be a victim of other conditions.

Smoke consists of small particles of solid material suspended in hot air and gases. Thus, smoke may be said to have a particulate fraction and a gaseous fraction. In general, the particulate fraction is obvious because it is visible, although it is probably less harmful than the invisible gaseous fraction. The relative amounts of the particulate and gaseous fractions vary a great deal in smokes from different sources. The particulate fraction may be small, and the smoke barely visible, yet contain large amounts of toxic gases.

Aldehydes in smoke

The particulate fraction of smoke is mostly carbon, a relatively innocuous substance, but the particles are usually coated with products of combustion. From the medical point of view, the most important of these are the organic aldehydes. The particulate fraction of smoke from different fires has a fairly constant composition except for the size of the particles and the relative amounts of different aldehydes present. For example, particles from burning petroleum products tend to be small and contain mostly acrylic aldehydes (acrolein) while those from wood smoke are large and contain a great deal of acetaldehyde.

The gaseous fraction, on the other hand, varies greatly in composition. Carbon monoxide and carbon dioxide are always present and account for the greatest bulk of the gaseous fraction as a rule. An almost endless variety of other gases may also be present, and some of these may be very toxic. These other gases may be products of combustion or substances leaked from storage or processing facilities and vaporized by the heat of the fire.

Because smoke is such a complex mixture of different substances, we should expect that exposure to smoke would lead a variety of different types of injury. This is indeed the case. There is no single injury or single set of symptoms common to all victims of smoke exposure. Each case must be diagnosed and treated individually, according to the type of injury present.

Lack of oxygen

The first injury due to smoke exposure that I wish to discuss is possibly the most familiar one—lack of oxygen.

We used to call this asphyxia, but the term hypoxia is more commonly used now. Hypoxia is present whenever the tissues of the body do not have sufficient oxygen available to meet their needs. In fire fighters, hypoxia may result if they enter an enclosed area in which the oxygen has been consumed by a fire or driven out by the space-occupying effect of smoke and gases.

Hypoxia may also be produced by exposure to carbon monoxide. It is important to remember that carbon monoxide can produce hypoxia even if the victim is breathing plenty of oxygen because the gas combines with the red blood cells and prevents them from carrying oxygen from the lungs to the tissues. Hypoxia, from one cause or another, is probably the most common cause of death in a fire victim, but it is encountered less often in fire fighters since they usually are able to bring an oxygen supply with them, either by ventilating the involved structure or by using self-contained breathing apparatus.

This is not to say that fire fighters do not become hypoxic, however, and’ when they do, it is often the result of several relatively small exposures to carbon monoxide in a single day. Since it takes many hours to eliminate carbon monoxide from the body, repeated exposure to even low concentrations of this gas may have a cumulative effect.

Damage fo brain

Regardless of how hypoxia is produced in any patient, the organ most seriously affected is the brain, and permanent damage to this vital structure may result from a few minutes of complete lack of oxygen. In spite of the great damage which hypoxia produces, there are few symptoms to indicate its presence until convulsions and coma occur in the advanced stages. Before this, there is only an increase in the pulse rate and an alteration in the patient’s personality and judgment to warn of difficulty.

Smoke particles are small by most standards, but the vast majority of them are too large to actually be inhaled into the lungs. The nose and mouth constitute an efficient filtering system for most smoke particles, which become stuck to mucous in these structures. Some particles become trapped by the mucous membranes of the eyes. As more and more particles are trapped in the nose and mouth, they are swallowed and enter the stomach and digestive tract.

These particles contain irritants—the organic aldehydes—and the mucous membranes of the eyes, nose, mouth, throat and stomach become congested and inflamed as a result. This irritation produces the familiar running nose, sore throat and burning eyes seen with smoke exposure. These symptoms are annoying but are not incapacitating.

Stomach irritation

On the other hand, irritation of the stomach by swallowed smoke particles frequently produces nausea and vomiting. These symptoms may be incapacitating as well as annoying. Thus, the particulate fraction puts men out of action more by its action on the gastrointestinal tract than by any action on the respiratory tract.

Some smoke particles, with their associated irritants, are small enough to enter the lungs, but they constitute only a minor part of the particulate fraction of smoke. Some coughing and minor chest pain may result, but until more evidence is accumulated by research, we must conclude that smoke particles have little significant effect on the respiratory system.

From the standpoint of health, the most dangerous part of smoke is the gaseous fraction. This fraction contains deadly carbon monoxide gas. It is perhaps less commonly appreciated that this fraction may contain many other toxic gases. For the sake of discussion, these other gases may be divided into those which primarily act to damage the lungs themselves and those which merely enter the body via the lungs to produce toxic effects elsewhere.

Pulmonary irritants

The gases which damage the lungs themselves are called pulmonary irritants. Among these are chlorine, phosgene, sulfur dioxide and ammonia. When these gases are inhaled, they react with water in the lungs to produce strong acids or alkalis. For example, the old refrigerating gas, sulfur dioxide, reacts with water to form some sulfuric acid—battery acid. One can easily imagine the damage to the lungs that would result from pouring battery acid into the windpipe!

Until fairly recently, fire fighters risked exposure to pulmonary irritant gases only in industrial fires or accidents, which resulted in the escape of these gases from storage tanks, commercial refrigerators or industrial processing equipment. The risk is much more common today because pulmonary irritants are commonly formed as combustion products during the burning of plastics, foam rubber and synthetic textiles, and these materials are found in increasing amounts and variety in all types of buildings.

The identity of some of the pulmonary irritants which may be formed by the combustion of synthetics is known. For example, burning a pound of polyvinyl chloride plastic may liberate as much as of a pound of deadly chlorine gas. The identity of many other irritant combustion products is not known as yet, but we know they are present from the severe injuries that result to exposed individuals.

The pulmonary irritant gases are particularly dangerous both because of severe injury to the lungs which they produce and because they are’ gases, which allows them to enter the lungs freely. As I have mentioned, the nose and mouth filter out particulate smoke and its associated irritants to a very significant degree, but they do not prevent gases from entering the lungs.

Danger signal

All fire fighters today should be aware of exposure to pulmonary irritants and should be taught to recognize cases of exposure to these gases. They can usually be recognized by the intense sensation of choking produced by trying to breathe this atmosphere. These gases are not just irritating to breathe. You can’t really breathe them. When a fire involving plastic or other synthetic materials produces this choking smoke, self-contained breathing apparatus should be worn by all exposed fire fighters.

Any man exposed for more than a few seconds without breathing apparatus should be referred to a physician for observation and treatment at once in spite of the fact that he feels well. There is a characteristic delay of from one to six hours between exposure to these gases and the onset of symptoms. After they appear, the patient may be dead in an hour or two. Treatment is most effective if given during the delay period before the onset of symptoms.

Although more research and study are needed on the identity of pulmonary irritant gases and their effects on the lungs, it appears now that these gases are the chief lung function hazard to which fire fighters may be exposed. A patient who survives a moderate to heavy exposure to these agents may be left with serious permanent lung damage, and it is possible that repeated exposure to small amounts of these gases over several years of fire fighting may result in chronic lung disease, even though none of the exposures was heavy enough to cause symptoms at the time.

The gaseous fraction of smoke may contain gases which are not directly harmful to the lungs but which enter the body through the lungs to produce toxic effects elsewhere. These gases may be formed by the combustion process. Carbon monoxide is the most common example of a toxic gas which is formed by combustion and enters the body via the lungs yet produces its toxic effects on structures other than the lungs. Another example is the extremely deadly gas, hydrogen cyanide, which is formed from the combustion of silk, wool, leather and certain nitrogen-containing plastics.

Other toxic gases which may be present in smoke are not combustion products but are liberated from storage or processing equipment. If the chemical released is not a gas under ordinary conditions, it may be converted to the gaseous state by the heat of the fire. The variety of substances to which a fire fighter may be exposed in this manner is almost infinite, and they may affect the body in many ways.

Self-contained breathing apparatus should be worn by all individuals exposed to smoke from fires involving any tvne of chemicals, and fire officers should make every effort to identify any chemicals present. This information should be given promptly to the physician treating smoke casualties so that he can administer the proper antidote or other specific therapy that may be indicated.

(Continued next month)