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Firefighting Hazards

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We thank the Edmonton Fire-fighters’ Union for their interest and generous support of the development of this chapter. The “Edmonton Sun” and the “Edmonton Journal” graciously allowed their news photographs to be used in the articles on firefighting. Ms. Beverly Cann of the Manitoba Federation of Labour Occupational Health Centre contributed invaluable advice on the article on paramedical personnel and ambulance attendants.

Fire-brigade personnel may be engaged on a full-time, part-time, paid-on-call or unpaid, volunteer basis—or on a combination of these systems. The type of organization employed will, in most cases, depend on the size of the community, the value of the property to be protected, the types of fire risk and the number of calls typically answered. Cities of any appreciable size require regular fire brigades with full crews on duty equipped with the appropriate apparatus.

Smaller communities, residential districts and rural areas having few fire calls usually depend upon volunteer or paid-on-call fire-fighters for either full staffing of their firefighting apparatus or to assist a skeleton force of full-time regulars.

Although there are a great many efficient, well equipped volunteer fire departments, full-time, paid fire departments are essential in larger communities. A call or volunteer organization does not lend itself as readily to the continuous fire-prevention inspection work that is an essential activity of modern fire departments. Using volunteer and call systems, frequent alarms may call out workers who hold other jobs, causing a loss of time with seldom any direct benefit to employers. Where full-time fire-fighters are not employed, the volunteers must come to a central fire hall before response can be made to a call, causing a delay. Where there are only a few regulars, a supplementary group of well-trained call or volunteer fire-fighters should be provided. There should be a reserve arrangement that make assistance available for the response of neighbouring departments on a mutual-aid basis.

Firefighting is a highly unusual occupation, in that it is perceived of as dirty and dangerous but is indispensable and even prestigious. Fire-fighters enjoy public admiration for the essential work that they do. They are well aware of the hazards. Their work involves intermittent periods of exposure to extreme physical and psychological stress on the job. Fire-fighters are also exposed to serious chemical and physical hazards, to a degree unusual in the modern workforce.


Occupational hazards experienced by fire-fighters may be categorized as physical (mostly unsafe conditions, thermal stress and ergonomic stress), chemical and psychological. The level of exposure to hazards that may be experienced by a fire-fighter in a given fire depends on what is burning, the combustion characteristics of the fire, the structure that is on fire, the presence of non-fuel chemicals, the measures taken to control the fire, the presence of victims that require rescue and the position or line of duty held by the fire-fighter while fighting the fire. The hazards and levels of exposure experienced by the first fire-fighter to enter a burning building are also different from those of the fire-fighters who enter later or who clean up after the flames are extinguished. There is usually rotation among the active firefighting jobs in each team or platoon, and a regular transfer of personnel between fire halls. Fire-fighters may also have special rank and duties. Captains accompany and direct the crews but are still actively involved in fighting the fire on site. Fire chiefs are the heads of the fire service and are called out only in the worst fires. Individual fire-fighters may still experience unusual exposures in particular incidents, of course.

Physical hazards

There are many physical dangers in firefighting that can lead to serious physical injury. Walls, ceilings and floors can collapse abruptly, trapping fire-fighters. Flashovers are explosive eruptions of flame in a confined space that occur as a result of the sudden ignition of flammable gas products driven out of burning or hot materials and combined with superheated air. Fire situations that lead to flashovers may engulf the fire-fighter or cut off escape routes. The extent and number of injuries can be minimized by intensive training, job experience, competency and good physical fitness. However, the nature of the job is such that fire-fighters may be placed in dangerous situations by miscalculation, circumstance or during rescues.

Some fire departments have compiled computerized databases on structures, materials and potential hazards likely to be encountered in the district. Quick access to these databases assists the crew in responding to known hazards and anticipating possibly dangerous situations.

Thermal hazards

Heat stress during firefighting may come from hot air, radiant heat, contact with hot surfaces or endogenous heat that is produced by the body during exercise but which cannot be cooled during the fire. Heat stress is compounded in firefighting by the insulating properties of the protective clothing and by physical exertion, which result in heat production within the body. Heat may result in local injury in the form of burns or generalized heat stress, with the risk of dehydration, heat stroke and cardiovascular collapse.

Hot air by itself is not usually a great hazard to the fire-fighter. Dry air does not have much capacity to retain heat. Steam or hot, wet air can cause serious burns because much more heat energy can be stored in water vapour than in dry air. Fortunately, steam burns are not common.

Radiant heat is often intense in a fire situation. Burns may occur from radiant heat alone. Fire-fighters may also show skin changes characteristic of prolonged exposure to heat.

Chemical hazards

Over 50% of fire-related fatalities are the result of exposure to smoke rather than burns. One of the major contributing factors to mortality and morbidity in fires is hypoxia because of oxygen depletion in the affected atmosphere, leading to loss of physical performance, confusion and inability to escape. The constituents of smoke, singly and in combination, are also toxic. Figure 1 shows a fire-fighter using self-contained breathing apparatus (SCBA) rescuing an unprotected fire-fighter who was trapped in a very smoky fire in a tire warehouse. (The fire-fighter being rescued ran out of air, took off his SCBA to breathe as best he could, and was fortunate enough to be rescued before it was too late.)

Figure 1.  Fire-fighter rescuing another fire-fighter who was trapped in the toxic smoke from a fire in a tire warehouse.


All smoke, including that from simple wood fires, is hazardous and potentially lethal with concentrated inhalation. Smoke is a variable combination of compounds. The toxicity of smoke depends primarily on the fuel, the heat of the fire and whether or how much oxygen is available for combustion. Fire-fighters on the scene of a fire are frequently exposed to carbon monoxide, hydrogen cyanide, nitrogen dioxide, sulphur dioxide, hydrogen chloride, aldehydes and organic compounds such as benzene. Different gas combinations present different degrees of hazard. Only carbon monoxide and hydrogen cyanide are commonly produced in lethal concentrations in building fires.

Carbon monoxide is the most common, characteristic and serious acute hazard of firefighting. Carboxyhaemoglobin accumulates rapidly in the blood with duration of exposure, as a result of the affinity of carbon monoxide for haemoglobin. High levels of carboxyhaemoglobin may result, particularly when heavy exertion increases minute ventilation and therefore delivery to the lung during unprotected firefighting. There is no apparent correlation between the intensity of smoke and the amount of carbon monoxide in the air. Fire-fighters should particularly avoid cigarette smoking during the clean-up phase, when burning material is smouldering and therefore burning incompletely, as this adds to the already elevated levels of carbon monoxide in the blood. Hydrogen cyanide is formed from the lower temperature combustion of nitrogen-rich materials, including natural fibres such as wool and silk, as well as common synthetics such as polyurethane and polyacrylonitrile.

Light-molecular-weight hydrocarbons, aldehydes (such as formaldehyde) and organic acids may be formed when hydrocarbon fuels burn at lower temperatures. The oxides of nitrogen are also formed in quantity when temperatures are high, as a consequence of the oxidation of atmospheric nitrogen, and in lower temperature fires where the fuel contains significant nitrogen. When the fuel contains chlorine, hydrogen chloride is formed. Polymeric plastic materials pose particular hazards. These synthetic materials were introduced into building construction and furnishings in the 1950s and thereafter. They combust into particularly hazardous products. Acrolein, formaldehyde and volatile fatty acids are common in smouldering fires of several polymers, including polyethylene and natural cellulose. Cyanide levels increase with temperature when polyurethane or polyacrylonitriles are burned; acrylonitrile, acetonitrile pyridine and benzonitrile occur in quantity above 800 but below 1,000 °C. Polyvinyl chloride has been proposed as a desirable polymer for furnishings because of its self-extinguishing characteristics due to the high chlorine content. Unfortunately, the material produces large quantities of hydrochloric acid and, sometimes, dioxins when fires are prolonged.

Synthetic materials are most dangerous during smouldering conditions, not in conditions of high heat. Concrete retains heat very efficiently and may act as a “sponge” for trapped gases that are then released from the porous material, releasing hydrogen chloride or other toxic fumes long after a fire has been extinguished.

Psychological hazards

A fire-fighter enters a situation that others are fleeing, walking into immediate personal danger greater than in almost any other civilian occupation. There is much that can go wrong in any fire, and the course of a serious fire is often unpredictable. Besides personal security, the fire-fighter must be concerned with the safety of others threatened by the fire. Rescuing victims is an especially stressful activity.

The professional life of a fire-fighter is more than an endless round of anxious waiting punctuated by stressful crises, however. Fire-fighters enjoy the many positive aspects of their work. Few occupations are so respected by the community. Job security is largely assured in urban fire departments once a fire-fighter is hired, and the pay usually compares well with other jobs. Fire-fighters also enjoy a strong sense of team membership and group bonding. These positive aspects of the job offset the stressful aspects and tend to protect the fire-fighter against the emotional consequences of repeated stress.

At the sound of an alarm, a fire-fighter experiences a degree of immediate anxiety because of the inherent unpredictability of the situation he or she is about to encounter. The psychological stress experienced at this moment is as great and perhaps greater than any of the stresses that follow during the course of responding to an alarm. Physiological and biochemical indicators of stress have shown that fire-fighters on duty have sustained psychological stress that reflects subjectively perceived patterns of psychological stress and activity levels at the station.

Health Risks

The acute hazards of firefighting include trauma, thermal injury and smoke inhalation. The chronic health effects that follow recurrent exposure have not been so clear until recently. This uncertainty has led to a patchwork of employment and workers’ compensation board policies. The occupational risks of fire-fighters have received a great deal of attention because of their known exposure to toxic agents. A large body of literature has developed on the mortality experience of fire-fighters. This literature has grown with the addition of several substantial studies in recent years, and a sufficient database is now available to describe certain patterns in the literature.

The critical compensation issue is whether a general presumption of risk can be made for all fire-fighters. This means that one must decide whether all fire-fighters can be assumed to have an elevated risk of a particular disease or injury because of their occupation. To satisfy the usual compensation standard of proof that the occupational cause must be more likely than not responsible for the outcome (giving the benefit of the doubt to the claimant), a general presumption of risk requires a demonstration that the risk associated with occupation must be at least as great as the risk in the general population. This can be demonstrated if the usual measure of risk in epidemiological studies is at least double the expected risk, making allowances for uncertainty in the estimate. Arguments against presumption in the specific, individual case under consideration are called “rebuttal criteria”, because they can be used to question, or rebut, the application of the presumption in an individual case.

There are a number of unusual epidemiological characteristics that influence the interpretation of studies of fire-fighters and their occupational mortality and morbidity. Fire-fighters do not show a strong “healthy worker effect” in most cohort mortality studies. This may suggest an excess mortality from some causes compared to the rest of the healthy, fit workforce. There are two types of healthy worker effect that may conceal excess mortality. One healthy worker effect operates at the time of hire, when new workers are screened for firefighting duty. Because of the strenuous fitness requirements for duty, this effect is very strong and might be expected to have an effect of reducing mortality from cardiovascular disease, especially in the early years following hire, when few deaths would be expected anyway. The second healthy worker effect occurs when workers become unfit following employment due to obvious or subclinical illness and are reassigned to other duties or are lost to follow-up. Their relative high contribution to total risk is lost by undercount. The magnitude of this effect is not known but there is a strong evidence that this effect occurs among fire-fighters. This effect would not be apparent for cancer because, unlike cardiovascular disease, the risk of cancer has little to do with fitness at the time of hire.

Lung Cancer

Lung cancer has been the most difficult cancer site to evaluate in epidemiological studies of fire-fighters. A major issue is whether the large-scale introduction of synthetic polymers into building materials and furnishings after about 1950 increased the risk of cancer among fire-fighters because of exposure to the combustion products. Despite the obvious exposure to carcinogens inhaled in smoke, it has been difficult to document an excess in mortality from lung cancer big enough and consistent enough to be compatible with occupational exposure.

There is evidence that work as a fire-fighter contributes to risk of lung cancer. This is seen mostly among fire-fighters who had the highest exposure and who worked the longest time. The added risk may be superimposed on a greater risk from smoking.

Evidence for an association between firefighting and lung cancer suggests that the association is weak and does not attain the attributable risk required to conclude that a given association is “more likely than not” due to occupation. Certain cases with unusual characteristics may warrant this conclusion, such as cancer in a relatively young non-smoking fire-fighter.

Cancer at Other Sites

Other cancer sites have been shown recently to be more consistently associated with firefighting than lung cancer.

The evidence is strong for an association with genito-urinary cancers, including kidney, ureter and bladder. Except for bladder, these are rather uncommon cancers, and the risk among fire-fighters appears to be high, close to or in excess of a doubled relative risk. One could therefore consider any such cancer to be work-related in a fire-fighter unless there is a convincing reason to suspect otherwise. Among the reasons one might doubt (or rebut) the conclusion in an individual case would be heavy cigarette smoking, prior exposure to occupational carcinogens, schistosomiasis (a parasitic infection—this applies to bladder only), analgesic abuse, cancer chemotherapy and urologic conditions that result in stasis and prolonged residence time of urine in the urinary tract. These are all logical rebuttal criteria.

Cancer of the brain and central nervous system has shown highly variable findings in the extant literature, but this is not surprising since the numbers of cases in all reports are relatively small. It is unlikely that this association will be clarified any time soon. It is therefore reasonable to accept a presumption of risk for fire-fighters on the basis of current evidence.

The increased relative risks for lymphatic and haematopoietic cancers appear to be unusually high. However, the small numbers of these relatively rare cancers make it difficult to evaluate the significance of the association in these studies. Because they are individually rare, epidemiologists group them together in order to make statistical generalizations. The interpretation is even more difficult because grouping these very different cancers together makes little sense medically.

Heart Disease

There is no conclusive evidence for an increased risk of death overall from heart disease. Although a single large study has shown an excess of 11%, and a smaller study confined to ischemic heart disease suggested a significant excess of 52%, most studies cannot conclude that there is a consistently increased population risk. Even if the higher estimates are correct, the relative risk estimates still fall far short of what would be required to make a presumption of risk in the individual case.

There is some evidence, primarily from clinical studies, to suggest a risk of sudden cardiac decompensation and risk of a heart attack with sudden maximal exertion and following exposure to carbon monoxide. This does not seem to translate into an excess risk of fatal heart attacks later in life, but if a fire-fighter did have a heart attack during or within a day after a fire it would be reasonable to call it work-related. Each case must therefore be interpreted with a knowledge of individual characteristics, but the evidence does not suggest a generally elevated risk for all fire-fighters.

Aortic Aneurysm

Few studies have accumulated sufficient deaths among fire-fighters from this cause to achieve statistical significance. Although one study conducted in Toronto in 1993 suggests an association with work as a fire-fighter, it should be considered an unproven hypothesis at present. Should it be ultimately confirmed, the magnitude of risk suggests that it would merit acceptance on a schedule of occupational diseases. Rebuttal criteria would logically include severe atherosclerosis, connective tissue disease and associated vasculitis and a history of thoracic trauma.

Lung Disease

Unusual exposures, such as intense exposure to the fumes of burning plastics, can certainly cause severe lung toxicity and even permanent disability. Ordinary firefighting may be associated with short-term changes similar to asthma, resolving over days. This does not appear to result in an increased lifetime risk of dying from chronic lung disease unless there has been an unusually intense exposure (the risk of dying from the consequences of smoke inhalation) or smoke with unusual characteristics (particularly involving burning polyvinyl chloride (PVC)).

Chronic obstructive pulmonary disease has been extensively studied among fire-fighters. The evidence does not support an association with firefighting, and therefore there can be no presumption. An exception may be in rare cases when a chronic lung disease follows an unusual or severe acute exposure and there is a compatible history of medical complications.

A general presumption of risk is not easily or defensibly justified in situations of weak associations or when diseases are common in the general population. A more productive approach may be to take the claims on a case-by-case basis, examining individual risk factors and overall risk profile. A general presumption of risk is more easily applied to unusual disorders with high relative risks, particularly when they are unique to or characteristic of certain occupations. Table 1 presents a summary of specific recommendations, with criteria that could be used to rebut, or question, presumption in the individual case.

Table 1. Summary of recommendations, with rebuttal criteria and special considerations, for compensation decisions.


Risk estimate (approximate)  


Rebuttal criteria

Lung cancer




- Smoking, previous occupational carcinogens

Cardiovascular disease




+ Acute event at or soon following exposure

Aortic aneurysm




- Atherosclerosis (advanced), connective tissue disorders, history of thoracic trauma

Cancers of genitourinary tract






+ Occupational carcinogens

- Heavy cigarette smoking, previous occupational carcinogens, schistosomiasis (bladder only), analgesic abuse, cancer chemotherapy (chlornaphazine), conditions resulting in urinary stasis

/ Coffee consumption, artificial sweeteners

Brain cancer





- Heritable neoplasms (rare), previous vinyl chloride exposure, radiation to head

/ Trauma, family history, smoking

Cancers of lymphatic and

haematopoietic system





- Ionizing radiation, previous occupational carcinogens (benzene), immunosuppressed state, cancer chemotherapy

+ Hodgkin’s disease

Cancer of colon and rectum







+ Low risk profile

- Familial syndromes, ulcerative colitis

/ Other occupational exposures

Acute lung disease





Circumstances of case

Chronic lung disease (COPD)





+ Sequela of severe acute exposure, followed by recovery

- Smoking, protease deficiency

A = epidemiological association but not sufficient for presumption of association with firefighting. NA = no consistent epidemiological evidence for association. NE = Not established. P = presumption of association with firefighting; risk exceeds doubling over general population. NP = no presumption; risk does not exceed doubling over general population. + = suggests increased risk due to firefighting. - = suggests increased risk due to exposures unrelated to firefighting. / = no likely contribution to risk.


Injuries associated with firefighting are predictable: burns, falls and being struck by falling objects. Mortality from these causes is markedly increased among fire-fighters compared to other workers. Jobs in firefighting have a high risk of burns, especially, include those involving early entry and close-in firefighting, such as holding the nozzle. Burns are also more commonly associated with basement fires, recent injury before the incident and training outside the fire department of present employment. Falls tend to be associated with SCBA use and assignment to truck companies.


Firefighting is a very strenuous occupation and is often performed under extreme environmental conditions. The demands of firefighting are sporadic and unpredictable, characterized by long periods of waiting between bouts of intense activity.

Fire-fighters maintain their level of exertion at a relatively constant, intense level once active firefighting begins. Any additional burden in the form of an encumbrance by protective equipment or victim rescue, however necessary for protection, reduces performance because fire-fighters are already exerting themselves to the maximum. The use of personal protection equipment has imposed new physiological demands on fire-fighters but has removed others by reducing exposure levels.

A great deal is known about the exertion characteristics of fire-fighters as a result of many careful studies on the ergonomics of firefighting. Fire-fighters adjust their levels of exertion in a characteristic pattern during simulated fire conditions, as reflected by heart rate. Initially, their heart rate increases rapidly to 70 to 80% of maximal within the first minute. As firefighting progresses, they maintain their heart rates at 85 to 100% maximal.

The energy requirements for firefighting are complicated by the severe conditions encountered in many inside fires. The metabolic demands of coping with retained body heat, heat from the fire and fluid loss through sweating add to the demands of physical exertion.

The most demanding activity known is building search and victim rescue by the “lead hand” (first fire-fighter to enter building), resulting in the highest average heart rate of 153 beats/minute and highest rise in rectal temperature of 1.3 °C. Serving as “secondary help” (entering a building at a later time to fight the fire or to conduct additional searches and rescues) is next most demanding, followed by exterior firefighting and serving as crew captain (directing the firefighting, usually at some distance from the fire). Other demanding tasks, in decreasing order of energy costs, are climbing ladders, dragging the fire hose, carrying a travelling ladder and raising a ladder.

During firefighting, core body temperature and heart rate follow a cycle over a period of minutes: they both increase slightly in response to work in preparation for entry, then both increase more as a result of environmental heat exposure and subsequently increase more steeply as a result of high work loads under conditions of heat stress. After 20 to 25 minutes, the usual length of time allowed for interior work by the SCBA used by fire-fighters, the physiological stress remains within limits tolerable by a healthy individual. However, in extended firefighting involving multiple re-entries, there is insufficient time between SCBA air bottle changes to cool off, leading to a cumulative rise in core temperature and an increasing risk of heat stress.

Personal Protection

Fire-fighters exert themselves to maximal levels while fighting fires. Under fire conditions, physical demands are complicated by the metabolic demands of coping with heat and loss of fluids. The combined effect of internally generated heat during work and of external heat from the fire may result in markedly increased body temperatures that climb to unusually high levels in an intense firefighting situation. Half-hour interval breaks to change SCBAs are not enough to arrest this climb in temperature, which can reach dangerous levels in prolonged firefighting. Although essential, personal protection, particularly SCBAs, imposes a considerable additional energy burden on the fire-fighter. The protective clothing also becomes much heavier when it gets wet.

The SCBA is an effective personal protection device that prevents exposure to the products of combustion when used properly. Unfortunately, it is often used only during the “knockdown” phase, when the fire is being actively fought, and not during the “overhaul” phase, when the fire is over but the debris is being examined and embers and smouldering flames are being extinguished.

Fire-fighters tend to judge the level of hazard they face by the intensity of smoke and decide whether to use an SCBA solely on the basis of what they see. This may be very misleading, after the flames are extinguished. While the fire scene may appear to be safe at this stage, it can still be dangerous.

The additional burden or energy cost of using personal protective equipment has been a major area of emphasis in occupational health research on firefighting. This undoubtedly reflects the degree to which firefighting is an extreme case of a matter of general interest, the implications for performance of using personal protection.

Although fire-fighters are obliged to use several forms of personal protection in their work, it is respiratory protection that is most problematic and which has received the most attention. A 20% decrement has been found in work performance imposed by carrying an SCBA, which is a substantial restraint under extreme and dangerous conditions. Investigations have identified several factors of importance in evaluating the physiological demands imposed by respirators in particular, among them the characteristics of the respirator, physiological characteristics of the user and the interactive effects with other personal protection and with environmental conditions.

The fire-fighter’s typical “turnout” gear may weigh 23 kg and imposes a high energy cost. Chemical protective clothing (17 kg), as used for clean-up of spills, is the next most demanding gear to wear, followed by the use of SCBA gear while wearing light clothing, which is only slightly more demanding than wearing light, flame-resistant clothing with a low-resistance mask. The firefighting apparatus has been associated with significantly greater retention of internally generated heat and rise in body temperature.


Numerous studies have evaluated the physiological characteristics of fire-fighters, usually in the context of other studies to determine the response to firefighting-related demands.

Studies of the fitness of fire-fighters have shown fairly consistently that most fire-fighters are as or somewhat more fit than the general adult male population. They are not, however, necessarily fit to an athletically trained level. Fitness and health maintenance programmes have been developed for fire-fighters but have not been convincingly evaluated for their effectiveness.

The entrance of female applicants into firefighting has caused a re-evaluation of performance tests and studies comparing the sexes. In studies of trained individuals capable of achieving their potential maximum performance, rather than typical applicants, women demonstrated lower scores on average than men in all performance items, but a subgroup of women performed nearly as well in some tasks. The overall difference in performance was attributed primarily to lower absolute lean body weight, which correlated most strongly and consistently with performance differences. The most difficult tests for women were the stair-climbing exercises.



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