Fires

Factors involved: Chemical reactions, geography, human activity, weather conditions, wind

Regions affected: All

Definition

Fires occur throughout the world as a result of many causes. They can inflict devastating damage to natural environments, cities, and buildings, causing billions of dollars in damage. Large fires can cause many deaths and injuries to people and animals.

Science

Fire occurs through the process of combustion. Combustion is an exothermic, self-sustaining, chemical reaction usually involving the oxidation of a fuel by oxygen in the atmosphere. Emission of heat, light, and mechanical energy, such as sound, usually occurs. An exothermic reaction is one in which the new substances produced have less energy than the original substances. This means that there is energy in various forms produced in the reaction. In fires, the energy is released primarily as heat and light.

A fuel is a material that will burn. In most environments, carbon is a constituent element. Many typical fuels must undergo a process called pyrolysis before they will burn. Wood, for example, exists in many buildings in the form of furniture and framing to support the walls and roof. In its normal condition, wood does not burn. It must be broken down through the application of heat into its constituent elements before it can be oxidized. This is the process of pyrolysis.

Oxidation is a chemical reaction in which an oxidizing agent and a reducing agent combine to form a product with less energy than the original materials. The oxygen is usually obtained from the air. The fuel is the reducing agent. For the process to begin, a source of heat must be applied to the fuel. This heat is needed to raise the temperature of the material to its ignition point, or the lowest temperature at which it will burn. Ignition can occur from a variety of natural and human sources. Electric wires or appliances can come in contact with combustible materials, raising their temperature. Natural sources such as lightning can start wildfires. People can deliberately start fires using an accelerant; arson is responsible for many fires throughout the world.

Three factors are necessary for a fire to begin. They are illustrated as the fire triangle of heat, fuel, and oxygen. A fire with these three elements will be a glowing fire. For self-sustaining combustion to occur, a fourth factor, a chain reaction, must be added to the original three factors. This converts the fire triangle to a fire tetrahedral, or four-sided pyramid. A chain reaction occurs when the heat produced by the fire is enough not only to burn the fuel but also to preheat the next segment of fuel so that the fire can grow. As long as the rate of heat production is greater than the rate at which heat is dissipated to the surroundings, more fuel can be ignited and the fire will spread. When the heat produced by the fire is dissipated to the surroundings, the fire will gradually decay.

A fire will continue until the available fuel is consumed, the available oxygen is used, the flames are extinguished by cooling, or the number of excited molecules is reduced. Fire extinguishment and prevention strategies are aimed at breaking or removing one leg of the fire triangle or tetrahedral.

In most fires, either the action of a person or an act of nature, such as a lightning strike, are required to bring the factors together for a fire to start. The act of a person may be deliberate, as in the case of arson; accidental, as in the case of someone falling asleep in bed with a lighted cigarette; or an act of omission, such as a building not being constructed in a safe manner.

There are two basic kinds of fires. A fuel-controlled fire is one that has an adequate amount of oxygen but has limited contact with fuel. A ventilation-controlled fire has access to adequate amounts of fuel but has limited contact with oxygen. The National Fire Protection Association (NFPA) has classified four classes of fires. Class A fires involve ordinary combustibles such as wood, paper, cloth, or fiber; they can be extinguished with water or foam. Class B fires involve flammable liquids, such as hot grease, paints, thinners, gasoline, oil, or other liquid fuels; they can be extinguished with a chemical foam or carbon dioxide. Class C fires, electrical fires, can be extinguished with a nonconducting extinguishing agent such as carbon dioxide or a dry chemical. Type D fires involve flammable metals, such as magnesium or sodium alloys, and they can be put out by smothering with a dry powder with a sodium chloride or graphite base.

Four basic mechanisms of heat transfer are involved in fires. Convection is heat transfer within a fluid. In most fires, this occurs within the air. As a fluid is heated, its molecules become less dense and rise. Air at normal density will move into the area of heat, replacing the less dense air that has risen. As this air is heated, it will also rise. This explains the natural movement of fire gases and smoke from lower areas to higher ones. Conduction is heat transfer between two bodies in direct contact with each other. Heat can be transferred through the molecules in a wall by conduction.

A combination of convection and conduction occurs between a solid and a fluid at their boundary. Radiant heat transfer involves heat transfer by electromagnetic waves across distances. A surface, such as a wall, that has been heated by a fire can transfer radiant heat across the room to heat another wall surface or a person’s skin even if there is no direct contact. This process occurs in the same way that the heat energy from the sun is transferred to the earth across millions of miles of space. The fourth form of heat transfer involved in fires is latent heat transfer. Latent heat is the heat that is involved in the change of state of a substance. In a fire, water used as an extinguishing agent will be converted to steam, absorbing large quantities of heat energy as it changes from a liquid to a gas.

A conflagration is a fire that spreads over some distance, often a portion of a city or a town. A large group fire spreads from building to building within a complex of buildings. The number of conflagrations and large group fires were substantially reduced in the twentieth century in the United States. This decrease is attributed to building codes that require fire-resistant construction of the exterior walls and roofs of buildings in cities, modern fire-department capabilities to extinguish fires, adequate urban water systems that have large quantities of water available for fire extinguishment, sprinkler systems in commercial buildings, and limits on openings between buildings that are located close to one another.

Three main types of conflagrations have occurred since 1950. The first are urban/wild land interface fires. An urban/wild land interface is the area where an urban or suburban area adjoins the natural or undeveloped environment. Fires may start in the wild land and be driven by strong winds and available combustibles into residential or urban areas over a large fire front that cannot be extinguished. The Oakland Hills fire of 1991 is an example of this type of fire. These fires were the most prevalent type of conflagration in the 1990s.

Conflagrations also occur in “congested combustible districts.” These fires are typical of urban conflagrations before the 1900s, when the need for streets wide enough for automobiles changed the character of cities around the world. The congested combustible district is one with narrow streets lined with continuous buildings. The Boston Fire of 1872 is an example of this type of fire.

Third, conflagrations can be driven by strong winds among houses with wood shingles or other flammable roofing materials. These fires often occur in the southwestern United States. Last, large group fires often occur in old manufacturing districts, where the buildings are abandoned or are poorly maintained. The fire in Chelsea, Massachusetts, in 1908 is an example of this type of fire.

Geography

Fires occur in all geographic regions of the world. Air as a source of oxygen is available in all environments that support human habitation. Fuels are also present in every environment. The trees and grasses in natural environments will become fuels for wildfires; the furnishings in homes, the materials used in the construction of many buildings, and the clothes people wear are all potential fuels in the presence of heat.

Most fires occur outdoors. These are often called wildfires or brushfires. Fires can occur in forests, grasslands, and farms (crop fires). Wildfires can be started either by an act of nature, such as a lightning strike, or by human actions. Many wildfires are started by accident or by carelessness. Examples of this include leaving a campfire unattended or discarding smoking materials through the window of a car into a natural area.

Trash fires, or the burning of debris in land clearings, can also spread beyond the point of origin. Forest management personnel often direct controlled burns in natural areas to burn underbrush, consume fallen limbs and dead plants, and rejuvenate the forest ecosystem. This practice is thought to reduce the hazard of wildfires because a large amount of fuel is consumed in a controlled manner. There are dangers, however, as in the Cerro Grande fire, in which a controlled burn grew into a major conflagration and destroyed hundreds of homes in Los Alamos, New Mexico, in May 2000.

Most deaths and injuries from fire occur in homes and garages. Historically, there have also been large numbers of deaths and injuries in public buildings, such as theaters, assembly buildings, schools, hospitals, stores, offices, hotels, boardinghouses, dormitories, and other community facilities. Modern building codes and construction practices have reduced the number and severity of these fires.

The industrial environment poses many serious fire hazards. Industry includes storage, manufacturing, defense, utility, and other large-scale operations. The presence of large amounts of potential fuel or volatile materials such as solvents in an industrial plant in a large open building constitute a potential fire threat.

Fires may also occur in structures that are not buildings, such as bridges, tunnels, vacant buildings, and buildings under construction. While much public fear and awareness of fire is centered on large fires in public buildings, most people who are killed in fires in the United States die in their homes or cars. In 2019, about 72.2 percent of fire deaths and 76.4 percent of fire injuries occured on residential properties.

The mobile environment is composed of trains, automobiles, airplanes, and other transportation vehicles. Many people die or are injured from fires that occur after vehicles crash or are otherwise involved in accidents. However, it is important to note that only one-sixth the number of people die in vehicle fires as die in home fires each year.

The dangers of fire to people and property are omnipresent. Therefore, strategies for design, fire protection, and fire prevention must reach everywhere. Significant progress appears to have been made in reducing fires that result in multiple deaths and large property losses.

Prevention and Preparations

Fires can be prevented by attacking each leg of the fire triangle or tetrahedral. Sources of heat, particularly open flames, must be isolated from fuels. This can be accomplished in several ways. Rooms that contain sources of heat, such as boiler rooms, mechanical plants, and shops, are usually built with fire-resistant enclosures to contain or compartmentalize the building. Electric wires and electrical appliances must be adequately insulated so the heat produced cannot escape to building materials or furnishings.

Fuels must be limited in wild lands and buildings. Controlled burns, described earlier, provide a method of decreasing fuels in the natural environment. Buildings can be constructed of and furnished with materials that are noncombustible. The amount of fuel in a building is often expressed as the amount of combustible materials by weight compared to an equivalent amount of wood. This is known as a fuel load. Products used in homes and commercial buildings can be redesigned to reduce their fire risk.

Most fires are the result of either careless or deliberate human behavior. Therefore, educating people about fire risks and appropriate fire-prevention strategies is an essential element in fire prevention. Educating the general public could potentially have the greatest impact on reducing the number and severity of fires, but it is perhaps the most difficult strategy to implement. Fire-protection authorities believe that to modify the behavior of the public with regard to fires requires more than a brief exposure to fire-safety education. The NFPA has produced the “Learn Not to Burn” curriculum material for use in schools across the United States, which consists of a series of exercises with which teachers may teach children of the dangers of fire, fire-prevention strategies, and methods of protecting themselves and their families in the event of a fire. The NFPA reported that in the 1990s only a small percentage of schools actually used this material, however.

The NFPA and many municipal fire departments regularly conduct community meetings and demonstrations of fire protection and prevention techniques, distribute brochures and educational kits, and conduct open houses during Fire Prevention Week activities. These efforts have been aimed at emphasizing actions to prevent fires and appropriate behaviors during fires.

Preparation for fires and protection during a fire can take several forms. Preparing for a fire consists of maintaining buildings to have limited fuels and heat sources. Fuels should be stored in protected areas, and electrical systems and other potential sources of heat must be properly maintained. Access to volatile substances should be limited. A fire-detection system, such as smoke detectors with audible and visible alarms that notify building occupants during the earliest stages of a fire, is an essential preparation component. If the detection system is attached to an automatic suppression configuration, such as a sprinkler system, the fire can be extinguished before it moves beyond the area of origin, reducing its threat to people and property. Providing fire extinguishers, standpipe systems, and other opportunities for manual fire suppression in buildings is also necessary. The fire-detection, alarm, sprinkler, and standpipe systems are called active fire protection systems.

Maintaining a fire department with adequate personnel and equipment is necessary if fires do start and are not suppressed by automatic equipment. A community emergency notification system, such as the 911 telephone line, is required to contact the fire department quickly to ensure that personnel can arrive at the scene with enough time to suppress a fire and rescue people.

Buildings are required to be designed to confine fires to the area of origin by a series of fire and smoke barriers that subdivide a building into a series of compartments. The use of fire- and smoke-resistant walls to confine fire spread is called a passive fire protection method. Other passive fire protection strategies include limiting the use of materials that contribute to fire growth and limiting the size of buildings based on the relative combustibility of their construction systems and contents.

Providing safe ways for people to leave a burning building is an essential method of fire protection. The path from a point inside a building to safety outside the building is called the means of egress. The means of egress consists of three components. The exit access is the unprotected path from any point in a building to an exit. This distance is limited in all buildings so people can move quickly to an exit. An exit is a fire-resistant, smoke-resistant enclosure that leads one from an exit access to the exit discharge, the opening that takes one from an exit to the safety of the “public way.” An exit may be a fire stairway in a tall building, a horizontal corridor, or doors that lead directly out of a building in a small, one-story structure. The number and size of exits are determined by how many people will use the building.

It is essential that the exits do not become overly congested during fire evacuations. Fire exits must be illuminated with lights connected to an emergency power source so that when the normal electric service in a building is interrupted during a fire, people can still find the exits in smoke-filled corridors. In very large buildings or in structures such as hospitals, where people cannot be moved out of the building, places of refuge are provided. A place of refuge is an area in a building that is protected from fire and smoke where people can move to await rescue. Conducting fire drills in homes, schools, workplaces, and other buildings is essential so people know how to react in the event of a fire. Many large buildings have voice systems for someone to provide evacuation instructions to occupants through loudspeakers on each floor.

Rescue and Relief Efforts

Three hazards are posed by fire: smoke inhalation, burns, and building collapse or explosion. Some of the gases present in a fire, such as carbon monoxide, hydrogen cyanide, and carbon dioxide, are narcotics or materials that cause pain or loss of consciousness. Particles and other gases can cause irritations of the pulmonary system or eyes, ears, and nose. Other gases, such as hydrogen chloride, are toxic in the quantities created during a fire. The combined effects of breathing these gases is called smoke inhalation. It is treated by removing people to a safe environment with clean air and administering oxygen.

Injuries and death in fires are primarily caused by the effects of smoke inhalation. Smoke consists of airborne solid and liquid particulates and gases that result from pyrolysis and combustion. The combustion process is never fully complete, so there are also a number of unburned fuel particles and gases in the smoke as well. Many of the particles are about the same size as the wavelength of visible light. Light is scattered by the smoke particles, making vision very difficult in smoke-filled rooms.

Heat is another major product of the combustion process. Typical building fires exceed temperatures of 1,000 to 1,500 degrees Fahrenheit. Human beings cannot survive temperatures of this magnitude. The skin will receive second-degree burns when exposed to temperatures of 212 degrees Fahrenheit for fifteen seconds. People will go into shock as a result of exposure to heat, irritants, and oxygen deficiency experienced even at the periphery of fires. This condition can lead to elevated heart rates that can bring on heart attacks.

Burns are classified as first, second, and third degree depending upon the damage done to the skin. First-degree burns are characterized by redness, pain, and sometimes a swelling of the outermost layers of the skin. Second-degree burns usually penetrate deeper into the skin than first-degree burns. Fluids accumulate beneath the skin, forming blisters. The skin becomes moist and pink. Third-degree burns result in dry, charred skin that exposes the layers beneath. Third-degree burns can be life-threatening and require special treatment.

People can also be injured or die in fires as a result of collapse of burning buildings and explosions. In some fires in large buildings there have been reports of panicked behavior contributing to fire deaths. The NFPA defines panic as a sudden and excessive feeling of alarm or fear, usually affecting a number of people, which is vaguely apprehended, originates in some real or supposed danger, and leads to competitive, fear-induced flight in which people might trample others in an attempt to flee. Fire investigators state that this type of panic does not occur in many fires.

It is often very difficult for fire rescue workers to remove people trapped in a building. In tall buildings, people must be evacuated by ladders or helicopters to areas of safety, where initial medical evaluation and treatment can occur. Rescue workers require special fire-resistant clothing and self-contained breathing apparatus to move into a fire scene to remove people without injuring themselves in the process. Fire-department personnel and emergency medical technicians are specially trained to remove people from fires and provide initial first aid. For those suffering from severe smoke inhalation or third-degree burns, special treatment is required. Many hospitals in large metropolitan areas have special burn centers to treat severe injuries. There have been incidents reported in which people have walked away from a fire scene only to die within a few days as a result of exposure to toxic gases.

Fire department personnel stay at a fire scene until the combustion process has stopped. In a large fire, smoldering can continue under a top layer of ash for some time after the fire has been apparently extinguished, only to restart at a later time when the wind blows some of the ash into contact with a new fuel.

Impact

The short-term effects of fire include damage to and destruction of property, including both buildings and natural lands; injury and death of people and animals; and a loss of homes or workplaces, which can have a lasting impact on an individual, a family, or a community. In the United States there are more than 1.3 million reported fires each year. Many estimate that the actual number of fires is much greater than this. There were 3,700 deaths and over 16,600 injuries from fires in 2019, resulting in $14.8 billion in property damage. Three out of five home fire deaths occur in homes without working smoke detectors. While there has been a steady decrease in fire deaths since 1980, attributed to requirements for the installation of smoke detectors in residences, the rates remain high, particularly in the southeastern states and Alaska. The fire death rates in the United States and Canada are almost twice those of other developed countries. Fire remains the third most prevalent cause of accidental death in homes, after falls and poisoning. Most of the 3,700 fire deaths in the United States occur in two segments of the population: the very young and the elderly.

Historical Overview

Throughout the history of civilization, humans and fire have been intimately intertwined. Mastery of fire provided a boon to prehistoric humans, and they used it to shape their environment. Primitive peoples used fire to drive game, that is, to force wild game into a small area of concentration, where the kill was much easier. As long as humans remained hunter-gatherers, use of fire was central to survival. Indeed, it has been suggested that the growing ability of such people to control the wild game population led to the extinction of many species.

When humankind converted from hunting to agriculture, fire was equally essential, for domestic fire was needed to convert the harvested grains into edible food for humans. The use of fire was at the heart of the growth in technology as well, for the manipulation of raw materials nearly always depended on fire: Pottery needed to be baked to make it usable as containers, and metals needed to be heated at ever higher temperatures to make the fluid metal that could be transformed into usable items.

Fire is a tricky tool and requires proper management. All too often, fire escapes from the control of the humans wielding it and creates devastation. A vast number of escaped fires were certainly never recorded: Little is known of the fire usages of Mesoamericans prior to the arrival of Europeans at the end of the fifteenth century, although there is archaeological evidence of their use of fire.

One of the earliest recorded instances of uncontrolled fire was the Great Fire of Rome, which burned much of the city during the reign of the Emperor Nero, in 64 CE. Part of Nero’s unsavory reputation comes from the apocryphal story that he relaxed while the city burned and destroyed the homes of hundreds of thousands of its citizens: “Nero fiddled while Rome burned.”

Countless unrecorded fires must have taken place during the collapse of the ancient civilization of Rome. At the time, wood was the principal building material, especially for domestic use, and many homes must have burned down when a cooking fire raged out of control. Occasionally such escaped domestic fires had unintended effects, notably when a large portion of the city of London burned in 1666: The city’s population had just been decimated by an epidemic of bubonic plague, carried by rats. When the houses burned down in the Great Fire of London, the rats burned with them, allegedly bringing an early end to the outbreak, although many historians dispute this claim.

It is known that American Indians used fire extensively, both to heat their dwellings and, particularly, to modify the environment. They used fire to clear the underbrush in the eastern United States, where otherwise forest cover dominated the landscape. Fire enabled them to rid a small portion of land of trees that they had girdled and of the brush that grew up when the trees died, leaving them a clearing where they could plant the corn, beans, and squash that formed an important part of their diet. They also burned the land to eliminate underbrush within the forest, making travel through it, as well as hunting, easier. These practices were adopted by the European settlers who, in any case, brought with them a tradition of the use of fire for land management.

Fire also shaped the environment without intervention by humans. In the parts of America where rainfall is scarce, lightning often strikes, especially during the summer. The grasslands of the Great Plains are believed to be largely the product of frequent widespread fires that burned over the land often enough to prevent trees from developing. As more American Indians were concentrated on the Great Plains, fire was used by them to manage the great herds of buffalo that grazed there. It was only as the Europeans began to establish settlements on the Great Plains that efforts were made to contain the grass fires.

Meanwhile, fire had become an important tool in warfare. In ancient times, barricades were generally made of wood, and many attempts were made to burn them by tossing burning brands into the area under siege. The development of what came to be known as Greek fire—material that would burst into flame on contact—made possible a more potent use of fire in sieges. In addition, it became the practice of conquering armies to set fire to urban centers they conquered. Napoleon I’s army burned Moscow in 1812, and Washington, DC, was burned by the British in 1814. In World War II, fire started by aerial bombardment became an important tool. Many fires were begun in London from 1940 through 1945 as a result of German bombardment known as the Blitzkrieg. The Allies retaliated by setting fire to both Hamburg, in 1943, and Dresden, in 1945. That same year, incendiary bombs rained down on Tokyo, burning large portions of the city.

As urban concentrations grew, the risk of fire grew with them. Portions of the city of Boston burned as early as 1679. In 1788, the city of New Orleans burned, as did the city of Hamburg in 1842. In 1850 and again in 1851, the city of San Francisco burned. The Great Chicago Fire destroyed much of that city in 1871, allegedly when a cow kicked over a kerosene lantern. In 1894, a part of the grounds and structures of the World Columbian Exposition in Chicago burned. Much of San Francisco burned again following the devastating earthquake of 1906.

A number of fires in individual buildings became major disasters. Perhaps the most infamous was the Triangle Shirtwaist Factory fire, in 1911, when 145 trapped workers died. On November 28, 1942, the Cocoanut Grove nightclub in Boston burned, causing 491 deaths. The MGM Grand Hotel in Las Vegas burned in 1980, and 84 people died. In March 1990, eighty-seven people were killed during a fire at the Happy Land social club. A chicken-processing plant in North Carolina burned on September 3, 1991, killing 25 workers. Eighty-six people died in 1993, following the Waco siege by federal agents at a cult compound in Texas. In February 2003, one hundred people were killed when pyrotechnics ignited soundproofing foam at the Station night club in West Warwick, Rhode Island, during a concert.

Although the number of victims of building fires in the United States has declined steadily, a number of such disasters continued to occur abroad in which the death toll exceeded one hundred. In 1960, a mental hospital in Guatemala City caught on fire, and 225 died. A movie theater in Syria burned the same year, with a loss of 152 persons. The following year, a circus caught fire in Brazil, killing more than three hundred. In 1971 and 1972, fires in a hotel and nightclub in South Korea and Japan, respectively, each claimed more than one hundred victims, as did a department store fire in Japan in 1973.

Large congregations of people are particularly at risk. In 1975 a fire in a tent city in Saudi Arabia resulted in the loss of 138 individuals; three hundred pilgrims to Mecca lost their lives in a similar fire in 1997. In 1977, 164 people were killed in Kentucky when a nightclub burned, as did one hundred people attending a Great White concert in Rhode Island in 2003 when pyrotechnics ignited soundproofing foam. A fire at a nursing home in Jamaica resulted in the deaths of 157 people. In 1994, a fire in a toy factory in Thailand killed 213 people, and the same year a theater in China burned, with some three hundred people losing their lives. In August 2015, a fire at a chemical storage warehouse set off a series of massive explosions in Tianjin, China, killing more than 170 people.

Besides localized fires in buildings, wildfires have been consistent causes of disaster, even though the loss of life has been much less dramatic. The most famous of these was perhaps the fire in Peshtigo, Wisconsin, in 1871, when at least 1,200 died. Large forest fires burned the same year in Minnesota and Michigan. In 1881 large portions of the northern half of the lower peninsula of Michigan were engulfed in forest fires. In 1894 fires broke out again in the northern, forested sections of Michigan, Wisconsin, and Minnesota, reappearing in 1908. All these fires were a product of the heavy logging that had taken place in the last thirty years of the nineteenth century and the first decade of the twentieth. By 1910 the north woods of the Great Lakes states were logged out, and the problem was transferred to the heavily timbered regions to the west.

In 1910, wildfires raged throughout the West and the Midwest; more than 6 million acres of national forestland burned, destroying large acreages of privately owned forestland as well. That year was the worst year in history of losses to forest fires, though it was to be rivaled by the years 1945, 1988, 1996, and 2008. The 2008 California wildfire season was one of the most devastating wildfire seasons in the twenty-first century, with more than 1.3 million acres burned and thirteen firefighters killed. In 2018, the Camp Fire in California became the most destructive fire in state history, burning over 150,000 acres and 18,000 structures, and causing the deaths of over eighty people. In August 2020, the August Complex burned over 1.03 million acres across Glenn, Lake, Mendocino, Tehama, and Trinity counties.

In the dry regions of the United States, as well as elsewhere in the world, forest and brushfires are common in drought years. Nearly every year there are brushfires in California and in the arid Southwest, where the brush accumulations grow rapidly. The spread of settlement into these regions has heightened the risk of disaster, and there is some evidence that arson plays a part. Aerial surveillance has helped to reduce the risk to individuals, and local and national agencies have developed new tools for fighting such conflagrations. Even so, tragedies sometimes occur: In July 1994, fourteen firefighters lost their lives in Glenwood Springs, Colorado, when a sudden wind gust moved a forest fire uphill at a rate of more than 100 feet per second. In June 2013, nineteen firefighters of the Prescott Fire Department's Granite Mountain Hotshots in Arizona were killed while attempting to contain a wildfire.

The huge forest fires that burned in and around Yellowstone National Park in 1988 attracted the attention of the world through television broadcasts. The United States Forest Service, which had for more than fifty years followed a policy of fire suppression, from the massive burns of 1910 until the late 1970s, had then changed its policy. It had become clear that, at least in the West, fire suppression, associated with the popular icon, Smokey Bear, had the effect of allowing large quantities of tinder to build up in the forest. Once a fire got started, the large amounts of fuel made it easy for the fire to expand into a major disaster. Thus the forest service had taken a “let it burn” policy, allowing fires that did not threaten people to burn, hoping to keep down the accumulation of brush. However, in 1988 the fires got away from the officials in control, and the public was outraged when more than 1 million acres burned around Yellowstone, America’s most-visited national park.

Huge forest fires in Alaska the same year drove the total of burned acreage to more than 3.5 million, and federal officials were forced to revise their fire policy. There was, after 1988, a greater use of what is called controlled burning, deliberately set fires that are confined to a limited area, designed to eliminate the buildup of combustible materials before they create massive conflagrations.

Forest fires will continue to be a problem, especially wherever drought conditions exist. In 1998, drought conditions in Indonesia led to extensive wildfires, some of them escaped fires that had been set by cultivators to open up new areas for farming. The smoke and haze from these fires spread all over Southeast Asia. In 1996, more than 6 million acres of US forestland burned, the worst fire year since 1951, when the last of the four wildfires in Oregon known collectively as the Tillamook burn took a heavy toll. In 2006, wildfires caused a record level of destruction in the United States, with a total of more than 9.8 million acres burned. In 2017, more than ten million acres burned in US wildfires.

There have been eight years in which more than 8 million acres in the United States burned since records began in 1960, all of which occurred in the twenty-first century: 2004, 2005, 2006, 2007, 2011, 2012, 2015, 2017, and 2020. As earth’s climate warms and drought conditions occur more frequently due to global warming, more large and destructive fires have an increasing probability.

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