What fires are classified as natural? Abstract natural fires. How to fight wildfires

Fire is an uncontrolled combustion that causes material damage, harm to the life and health of citizens, and the interests of society and the state.

Approximately 80% of all fires occur due to human fault due to violation of measures fire safety when handling fire, as well as as a result of using faulty equipment. It happens that fires occur as a result of a lightning strike during a thunderstorm.

A natural fire is an uncontrolled combustion process that spontaneously arises and spreads in the natural environment.

Wildfires are divided into forest and steppe fires.

Forest fire is a spontaneous or human-caused fire in forest ecosystems.

On the territory of the Russian forest fund, from 10 to 30 thousand are registered annually. forest fires, often taking on the character natural Disasters. The bulk of the area covered by the fire was in the regions of Siberia and the Far East. In these areas, forest fire is a forest-forming factor that determines the structure and dynamics of the forest fund.

The most important characteristic of a forest fire is the speed of its spread, which is determined by the speed at which its edge moves, i.e. burning stripes along the fire contour.

Forest fires, depending on the area of ​​fire spread, are divided into ground fires, crown fires and underground fires (peat fires).
Ground fire is a fire that spreads along the ground and through the lower tiers of forest vegetation. During a surface fire, the forest floor, grass and shrub cover, undergrowth and undergrowth burn.

Ground fire most often occurs in deciduous forests, with the flame height reaching 1.5-2 meters, and the spread speed usually does not exceed 1-3 meters per minute, the fire temperature in the fire zone is 400-900 ° C. Ground fires are the most frequent and account for up to 98% of the total number of fires.

A crown fire is the most dangerous. It begins in strong winds and covers the crowns of trees. The fire moves through the crowns of trees, its spread speed in calm weather can reach 3-4 km/h, in windy weather - 25-30 km/h or more.

The conductor of combustion during crown fires is the layer of needles, foliage and branches of the crown space. The temperature in the fire zone rises to 1100°C. The wind carries burning sparks, which create new fires several tens or even hundreds of meters from the main source.

An underground (peat) fire is a fire in which the peat layer of marshy and swampy soils burns. It is characterized by a low advance speed (about 0.5 m/min). A characteristic feature of peat fires is the flameless combustion of peat with the accumulation of a large amount of heat. Peat fires are characterized by the fact that they are very difficult to extinguish. The cause (ignition) of a peat fire is overheating of the surface of a peat bog, drained or natural, when its surface is overheated by the rays of the sun or as a result of careless handling of fire by people.

The causes of fires in steppe and grain massifs can be thunderstorms, accidents of ground and air transport, accidents of grain harvesting equipment, terrorist attacks and careless handling of open fire. The most fire-hazardous conditions occur in late spring and early summer, when the weather is dry and hot.

Fire extinguishing methods

The simplest and at the same time sufficient effective way extinguishing weak and medium fires is to overwhelm the edge of the fire. For this, bunches of branches 1-2 m long or small trees, mainly deciduous, are used. A group of 3-5 people in 40-50 minutes can extinguish the edge of a fire with a length of up to 1000 meters.

When engulfing the fire does not give the desired effect, you can throw loose soil over the edge of the fire. To do this, it is best to use special equipment, but sometimes you have to do it manually. One person can cover about 20 meters of the fire edge in half an hour.

To prevent the fire from spreading further, earthen strips and wide ditches are arranged along the path of its movement. The strips should be free of vegetation and any other materials that promote combustion. When the fire reaches such a stripe, it stops.

Counter fire is widely used to fight fires, when another counter fire is created towards the moving shaft of fire. When these two shafts meet, the fire has nowhere to spread. When organizing a counter shaft, it is necessary to take into account the direction of the wind and the direction of fire spread.

If the fire cannot be stopped and it is approaching a populated area, in addition to taking all fire-fighting measures, the population should be evacuated. The withdrawal or removal of people should be carried out in a direction perpendicular to the spread of the fire. In this case, you should move not only along roads, but also along streams and rivers, and, if necessary, along the water itself. It is advisable to cover your mouth and nose with a wet cotton-gauze bandage or towel.

Indirect signs of an approaching forest fire are:

Persistent burning smell carried by the wind;
foggy smoke spreading over the forest;
restless behavior of animals, birds, insects;
night glow, at one of the points on the horizon, gradually expanding to the sides.

If a fire is detected, you should:

Do not rush around and do not panic;
analyze the situation, determine the evacuation route, why climb to a high point on the ground or climb onto tall tree and look around carefully. Identify the boundaries of the fire, the direction and approximate speed of its spread;
shelter from fire should be on bare islands and shallows located in the middle of large lakes, on bare areas of swamps, on rocky tops of ridges located above forest level, on glaciers;
it is necessary to move away from the fire in the windward direction (that is, go into the wind), in a direction perpendicular to the spread of the fire, trying to bypass the fire from the side in order to go to its rear.

Rules of conduct in a fire:

It is necessary to clear the largest possible area around you from foliage, grass and branches;
it is necessary to moisten the clothes generously, it is advisable to cover the mouth and nose with a wet cotton-gauze bandage or towel, remove all melting clothing;
get rid of flammable and flammable equipment; if possible, periodically wet dry areas of material on clothing;
burrow into wet soil;
wrap the head, limbs, open areas of the body with any non-flammable material, if possible moistening it with water, but not very tightly, so that in case of fire it can be removed instantly.

In dry seasons and in fire-hazardous places, special care should be taken when handling fire:

The place intended for the fire must be cleared of dry grass, leaves, branches and other forest debris;
do not light a fire near the overhanging crowns of trees, in young coniferous forests, among dead reeds and on peat bogs;
do not leave the fire unattended;
do not leave the resting place without making sure that the fire is extinguished;
in the steppe it is better to make a fire in areas of bare ground;
there should always be a fireman on duty near the fire;
If small fires arise, they must be extinguished immediately: pour water, cover with sand, earth, cover with pieces of tarpaulin, covering the access to oxygen, trample and knock down with wet rags or bunches of branches;
It is strictly unacceptable to set fire to a forest for the purpose of sending a distress signal.

The main types of injuries in fires are burns and carbon monoxide poisoning. When providing assistance, it is necessary, first of all, to extinguish the burning clothing of the victims, and apply sterile bandages to the burned surface. If people are affected by carbon monoxide, they should immediately remove them from areas of intense smoke and, if necessary, perform artificial respiration.

It should be remembered that emergency situations can be accompanied by various infectious diseases that can be contracted by eating dirty and contaminated water, food, as well as by infection through damaged human skin, etc.

A natural fire is an uncontrolled combustion process that spontaneously arises and spreads in the natural environment. The main types of natural fires are forest, peat and steppe.

A forest fire is an uncontrolled burning of vegetation that spontaneously spreads to a forest area surrounded by unburned territory (Fig. 23). The forest area through which the fire spreads includes open forest spaces (clearings, burnt areas, etc.). Forest fires represent greatest danger for people and farm animals.

Rice. 23. Forest fire

Under forest fire emergency refers to the situation in a certain territory that has arisen as a result of the occurrence of a source of natural emergency - a forest fire (forest fires), which can result or has resulted in human casualties, damage to human health and/or the natural environment, significant material losses and disruption of people's living conditions .

The territory within which a fire arose and spread as a result of natural disasters, accidents or catastrophes, or careless actions of people is called a fire zone. The space adjacent to the combustion zone and filled with smoke is called smoke zone.

The edge of a fire is a burning strip continuously moving along a combustible material, on which the main combustible material burns with maximum intensity and forms a shaft of fire.

The fire front is the fire edge that spreads most quickly in the direction of the wind. The edge of the fire moving against the wind is called

the rear of the fire, and perpendicular to the wind - the flanks of the fire.

Combustion is a physical and chemical process with the release of heat and light. For combustion to occur, the following must be present: a combustible material, an oxidizer, and an ignition source. Forest combustible materials are plants, their morphological parts and plant remains of varying degrees of decomposition.

The main causes of forest fires include: human activity, lightning discharges, spontaneous combustion of peat chips and agricultural fires in hot weather or during the fire season, i.e. the period from the melting of the snow cover in the forest until the appearance of a full green cover or the onset of stable rainy autumn weather.

Economic damage to the national economy from forest fires is divided into direct and indirect. Direct damage consists of wood loss, while indirect damage manifests itself in loss of agricultural land, disruption of communications, etc.

All forest fires pose an extreme danger, since by the time they are contained they manage to cover large areas, and there are not enough means to combat them. This creates a threat of destruction by fire. settlements and national economic facilities located in forested areas, as well as heavy smoke and gas pollution in populated areas remote from forested areas.

Zone of individual fires- this is an area in which fires occur in separate areas and in separate zones. Such fires are dispersed throughout the region, so it is possible to quickly organize their mass extinguishing using available forces and means.

Zone of massive and continuous fires - this is an area where so many fires and fires have occurred that it is impossible for the relevant units (formations) to be present in it without carrying out localization or extinguishing measures, and rescue operations are practically excluded. Such zones arise when there is continuous development of a forest area, a large amount of flammable materials, etc.

A special form of continuous fire is a firestorm, characterized by the presence of possible flows resulting from the combustion of a large amount of materials and forming a convection flow (column), towards which air masses rush at a speed of more than 15 m/s.

The formation of a firestorm is possible under the following conditions: the presence of buildings or the spread of flammable liquids over the area

less than 100 hectares; relative air humidity less than 30%;

the presence of a certain amount of combustible materials in the corresponding area (in terms of wood 200 kg/m2 in an area of ​​1 km2).

Area of ​​fires and smoldering in the rubble characterized by heavy smoke and prolonged (over 2 days) burning in the rubble. The work of the relevant fire departments is limited due to the danger to human life posed by thermal radiation and the release of toxic combustion products.

Dangerous smoke in open areas is considered to be one in which visibility does not exceed 10 m. The concentration of carbon monoxide in the air of about 0.2% causes fatal poisoning within 30...60 minutes, and 0.5...0.7% - within several minutes .

The cause of death may be a general increase in the temperature of the smoky environment. Inhalation of combustion products heated to 60 °C, even with 0.1% carbon monoxide in the air, usually leads to death.

Depending on the nature of the fire and in which elements of the forest the fire spreads, fires are divided into grassroots, crown and underground (soil).

A weak soil (underground) fire is one in which the burning depth does not exceed 25 cm, medium - 25...50 cm, strong - more than 50 cm.

Features of large forest fires:

occur during dry periods, most often with strong winds; take place against the backdrop of a massive outbreak of small and medium-sized fires; lasts several days; spread at high speed;

the nature of combustion at the edge is very diverse; easily overcome various barriers and obstacles (mineralized

lanes, roads, rivers); cause heavy smoke in large areas, making it difficult

actions of aviation and ground firefighting forces.

Ground forest fires develop during the combustion of coniferous undergrowth, dead (fallen needles, leaves, bark, as well as dead wood, stumps) and living ground cover (mosses, lichens, grass, shrubs). The front of the ground fire advances in a strong wind at a speed of up to 1 km/h, the flame height reaches 1.5...2 m.

Ground-level forest fires can be fugitive and persistent.

Runaway ground fires characterized by burning of forest litter, logging residues, vegetation cover, bark of the lower part of trees, exposed roots, bushes and undergrowth. Depending on the wind strength, their speed ranges from several hundred meters to 1.5 km/h; flame height

depends on the nature of combustible materials and reaches 0.1...2.0 m; The main combustion is fiery.

Sustained ground fires spread slowly. They are distinguished by the complete combustion of living and dead ground cover; combustion is flameless. During such fires, not only the soil cover, forest debris, undergrowth and undergrowth burn, but also trees with low branches. The ground cover burns completely; There are no areas left untouched by the fire. The bark and exposed roots of trees burn more deeply and severely.

Crown forest fires occur when the ground cover and strip of tree stand burn. They arise from the grassroots as a further stage of their development, and the grassroots fire is an integral part of the crown fire. How

And grassroots, they have a pronounced edge, which in the rear part represents a grassroots fire, and in the wind also the rear, flanks and front, advancing in the form of a top fire.

The speed of spread of crown forest fires reaches 25 km/h. They usually develop from ground fires in dense coniferous forests when drought and wind combine. Crown fires, like ground fires, can also be fugitive and persistent.

Sustained crown fires occur when the fire moves as a solid wall from the ground cover to the tree crowns at a speed of up to 8 km/h, while the tree crowns burn as the edge of the ground fire moves. In such fires, a large mass of sparks and ignited material is formed, flying in front of the fire front. Fire, if there is no wind, spreads through the thickness of the combustible material (peat), which partially or completely burns down to the mineral layer; trees can also burn out completely or partially; the grass cover sometimes remains and may turn yellow.

Runaway crown fires characterized by the separation of combustion along the canopy from the edge of the ground fire, while the fire spreads at a speed of up to 25 km/h. During a running fire in high winds, the crowns of coniferous trees burn; the fire spreads in leaps and bounds, with enormous speed, forming long, elongated tongues of flame; The speed at which a quick fire spreads in the wind reaches 8...25 km/h. The spread of combustion can outpace the advance of the edge of the ground fire. This occurs due to the transfer of burning sparks and firebrands by the wind.

And the formation of new combustion centers ahead of the fire front.

Underground (soil) forest fires are also a further stage in the development of ground fire. They occur in areas with a thick layer of litter (more than 20 cm) or with peaty soils. The fire usually enters the soil near tree trunks. Combustion occurs slowly and flamelessly. When the roots burn, trees fall randomly, forming rubble. The depth of burnout in a strong underground fire is more than 0.5 m, in a medium fire - up to 0.5 m and in a weak one - up to 0.25 m.

The degree of fire danger in forest areas is determined based on the table. 16.

Table 16

Scale for assessing forest areas according to the degree of fire danger

A peat fire is an uncontrolled process of smoky combustion of peat in the places of its formation, extraction and storage. Peat is a young geological formation that arises as a result of the death of swamp vegetation with an excess amount of moisture and insufficient air access. The accumulation of peat in a certain area in the form of layers of homogeneous or different in character and thickness is called peat deposit.

Under the influence of temperature, humidity and other reasons, peat gradually decomposes. The higher the degree of decomposition, the more susceptible it is to fire. Peat fires are possible throughout the year, but most often it occurs in the second half of summer, when the peat dries out.

Peat burns slowly, throughout its entire depth; Soil, equipment, people, and houses fall into the burnt areas. A characteristic feature of peat fires is the flameless combustion of peat with the accumulation of a large amount of heat. As a rule, there is no fire on the surface of the soil; it only breaks out here and there and soon disappears, but creeping smoke is released.

The main causes of peat fires are: spontaneous combustion of peat as a result of self-heating; exposure to sparks from fire sources and operating machines; lightning discharges, etc. The process of spontaneous combustion of peat has four periods of temperature change, lasting up to a year, during which the temperature inside the peat deposit rises to 60 °C and above.

Peat stored in piles at the extraction site also poses a serious fire hazard. When heated, it turns into a dry feathery mass - semi-coke, which spontaneously ignites when it comes into contact with oxygen in the air. In this case, separate hidden combustion sources are formed, detected by the emitted smoke. The burnout rate of peat in calm weather or low winds is approximately 0.18 kg/m2.

The rate of spread of a peat fire is small - a few meters per day. Such fires are not affected by daily weather changes or wind. They can last for months, even in rain and snow. When the wind speed is 3 m/s and higher, burning peat particles are often scattered in the wind over a considerable distance, which causes the spread of the fire.

The shape of a peat fire can be different: most often circular and angular, rarely rectangular. A peat fire is characterized by high temperatures in the combustion zone and heavy smoke.

Three periods can be distinguished in the development of a peat fire:

1) peat fire (small hearth area, low burning rate, low temperature and low smoke);

2) intense combustion, increase in combustion speed and temperature;

3) a period of high combustion temperature, heavy smoke and large area distribution.

Steppe (field) fires- These are fires that occur in open steppe areas with dry vegetation. In strong winds, the fire front moves at speeds of up to 25 km/h. If grain crops are burning, the fire spreads slowly.

Based on intensity, forest fires are classified into weak, medium and strong. The intensity of combustion depends on the condition and supply of combustible materials, the slope of the terrain, the time of day and especially the strength of the wind.

The speed of fire propagation under the influence of thermal radiation (radiation) of the flame increases when the fire front moves up the slope. Based on the speed of fire spread, ground and crown fires are divided into stable and fugitive. The speed of spread of a weak ground fire does not exceed 1 m/min, a medium one - 1...3 m/min, a strong one - over 3 m/min. A weak crown fire has a speed of up to 3 m/min, a medium one - up to 100 m/min, and a strong one - over 100 m/min.

The average speed of underground fire movement is low and amounts to 0.1 m/min, and sometimes less. The height of a weak ground fire is 0.5 m, a medium one is 1.5 m. If the height of a ground fire does not exceed 1.5 m, then it is considered strong.

The configuration of any large fires is unstable and depends on the direction and strength of the wind, the presence of areas with flammable material, and water boundaries, i.e., it is probabilistic in nature. In areas of forest fires, extensive smoke zones arise, visibility is sharply reduced, and cases of poisoning of people and animals with carbon monoxide are common. Wildfires can cause emergency, especially when they paralyze communications and affect populated areas.

Let's give short description fire propagation using a model that assumes two mechanisms that determine the development of a fire: thermal radiation and scattering of burning particles.

The determining parameters for the development of a fire over a large area are the average linear speed of its spread in the predominant direction and the rate of burning of materials depending on the surface wind speed at a certain moisture content of the materials. Usually, for calculations, the average value of their humidity is taken depending on the relative humidity of the air.

Based on an analysis of the parameters of real fires in large areas(burning of wood materials, wooden buildings, etc.) a formula was obtained for determining the linear speed of fire propagation, provided that its front has already formed and occupies 5...6 m (time from the start of the fire is 10 minutes):

v l = 0.55v 0.7,

where v is wind speed, m/s.

The linear speed of fire spread normal to the wind direction is calculated depending on its speed (flank development of the fire) using the formula

v fl = 0.488 · v 0.37.

The average linear speed of propagation of the fire front in the presence of wind is calculated as follows:

v = 3.333K g Сv n,

where K g is the distribution density of combustible materials, 0

In field conditions, peat combustion occurs on the surface of the spread or caravans with a slow deepening into the deposit or caravan. If there is no or little wind, the peat burns slowly. However, even at wind speeds of more than 3 m/s, burning peat particles are transported in the direction of the wind over considerable distances. The linear speed of combustion propagation, m/s, and the range of transfer of burning particles, m, are determined by empirical formulas

v 2.5 2 v l 8.88,

L v l 4 2 .

These formulas are valid for milled peat with a moisture content of up to 31%

And wind speed 4…14 m/s.

IN As a result of fires in peat fields, an empirical formula was obtained to determine the linear speed of combustion propagation in the direction of the wind:

v l v 24.64.

When assessing the effectiveness of measures to protect the population from thermal effects, it is necessary to determine the zone of thermal impact of the fire and the values ​​of heat flows at the source. The heat flux intensity of 3500 W/m was taken as the far boundary of the heat impact zone. A person's presence in a heat-affected area leads to burns of varying severity. The heat dose received during stay in various zones of thermal influence is expressed by the value

T di g kt k, k 1

where i is the number of areas with different values ​​of heat flows in which the population will be during its protection; g k t k are the values ​​of heat flows and the time of stay of the population in the k-th zone.

The toxodose dose received by a person during his stay in a gas-contaminated zone is expressed by the value

Tck tk,

where n is the number of areas with different concentration values ​​where the population will be located; c k t k are the concentration values ​​of combustion products and the time of stay of the population in the k-th zone, respectively.

6. MASS DISEASES OF PEOPLE, ANIMALS AND PLANTS

6.1. SOURCES, REASONS

AND WAYS OF SPREAD OF INFECTIOUS DISEASES

Infectious diseases are diseases caused by living pathogens. Of the countless number of microorganisms that inhabit the Earth, only pathogenic (disease-causing) species have the ability to cause disease.

The process of interaction of a pathogenic microbe with an animal (plant) organism under difficult environmental conditions is called infection. In other words, infection means the penetration of a pathogenic microbe into the body and its reproduction in the body.

Pathogenicity is the ability of a microorganism to multiply in the tissues of a macroorganism and, overcoming its protective functions, cause disease. This property is associated with the presence of pathogenicity factors in pathogenic microbes, which include invasiveness, toxicogenicity and the ability to form a capsule.

Invasiveness is the ability of pathogenic microbes to penetrate the body and spread in its tissues. It is caused by various enzymes produced by the microorganism.

Under toxicogenicity refers to the ability of pathogenic microbes to form toxic substances for the macroorganism - toxins. The toxin released by a living microbe is called exotoxin, and the toxin released when the microbe is destroyed is called endotoxin.

Some microbes, after entering the body, are able to form a capsule - a special protective shell.

The existence of a pathogenic microbe as a species in nature is determined by its ability to pass from one organism to another. In this case, the next transition and, consequently, a new infection and disease occur before the time spent by the pathogen in the previous organism or vector ends. Such a continuous chain of infections and diseases following one another, or bacterial carriage, is commonly called

become an epidemic process or an epidemic.

An epidemic process can arise and develop only if three mandatory conditions are present: a source of infection, routes of transmission of infection, and a group susceptible to the disease.

Infectious diseases that are unique to humans are called anthroponoses; those that are characteristic of humans and animals are called zoonoses. Diseases associated with wild animals are classified as natural zoonoses, while diseases associated with domestic animals are classified as domestic zoonoses. With some zoonoses (tularemia, etc.), a person, easily becoming infected from an animal, is himself a kind of “dead end” of infection. In such cases, human-to-human transmission is not observed, although theoretically this possibility cannot be excluded.

The transmission of some infectious diseases (rabies, chancroid, gonorrhea, venereal diseases, etc.) occurs without the participation of environmental objects, through direct contact of a sick organism with a healthy one. As a rare exception, some other diseases can also be transmitted through direct contact, although in these cases we are talking about less epidemiological significance.

The ways of spreading infection are very diverse. Contact and household infection is transmitted through household items

(dishes, linen, books, etc.), patient care items and production items (for example, when processing animal raw materials - hair, skins, etc.). This is the main route of spread of infection when the outer skin is infected, less often - with intestinal infections, especially in unsatisfactory sanitary conditions and non-compliance with the necessary hygienic rules in everyday life and at work.

Infectious diseases such as influenza, tuberculosis, diphtheria, scarlet fever, measles, mumps and many others are spread by air. Air ranks first in terms of ease of transmission of infection. The pathogen, released from the body of a patient or carrier with droplets of mucus, quickly enters the respiratory tract of a healthy person (airborne infection), settles on surrounding objects, and spreads with dust rising into the air (airborne dust infection). Dust can transmit diseases whose pathogens tolerate drying, in particular tuberculosis. In addition, the air can easily be contaminated artificially.

Infection through water occurs when contaminated water is used for drinking, household and household needs, and when bathing. Contamination of water in water pipes and large containers is especially dangerous. Infectious diseases spread by water include cholera, typhoid fever, leptospirosis, etc.

The food route is also common in the spread of infectious diseases. Pathogenic microbes can enter food products through the dirty hands of a patient or carrier, when washing food products in an infected

water, during transportation on random transport, cutting food products on dirty tables, infecting them with flies, rodents, etc.

Infection through soil occupies a special place in the transmission of infection. On the one hand, soil serves as a temporary residence site for pathogens of a number of diseases (anthrax, tetanus, etc.), and on the other hand, it plays a specific role in the spread of such types of worms as roundworms, hookworms, and whipworms. The eggs of these worms acquire the ability to cause infection only after “ripening” in the soil.

V body of a mosquito). Because of this, the carrier becomes infectious some time after feeding on the patient’s blood.

IN In some cases, for example, with tick-borne encephalitis, the virus can be transmitted to the offspring of the tick. Therefore, insects and especially ticks are not only carriers of infection, but often its guardians (reservoir)

V nature. The mechanism of infection transmission itself differs among different carriers. Thus, a mosquito and sandfly introduce infection to a person through a bite with saliva, a louse releases typhus pathogens with feces, which are rubbed into the skin when scratched, etc.

The massive spread of infectious diseases of the same name is called an epidemic. Separate groups of diseases are interconnected by common sources of infection or common routes of spread (for example, a water epidemic of typhoid fever and cholera, a tularemia epidemic of “mouse” or water origin, etc.).

A pandemic is an unusually severe epidemic that affects a large number of people in an area that extends beyond the borders of one state. The constant presence of any infectious disease in a certain territory is called endemic.

When assessing the extent of disease spread among animals, similar terminology is used. The concepts of epidemic, pandemic, and endemic correspond to such terms as epizootic, panzootic and enzootic.

It is worth noting that many animals - carriers of infection - live only in certain climatic zones and are not found outside them. Closely related to this is the spread of, for example, plague in desert-steppe areas, tularemia in floodplains of rivers and lakes, tick-borne encephalitis in taiga areas, etc.