External signs of external and internal fires. Causes of natural fires and their classification

A forest fire is the uncontrolled spread of fire through a forest area. In any situation, even a small fire can develop into a natural disaster. Currently, the probability of fire and large-scale spread of fire due to natural factors does not exceed 20%. Most forest fires are caused by human activity.

The following are the main causes of forest fire:

1. natural factors. For example, lightning strikes during a thunderstorm, spontaneous combustion of peat and vegetation during prolonged drought;
2. anthropogenic factors. They are mainly associated with planned arson to clear areas of logging waste and prepare them for new plantings and subsequent deforestation. But there are also fires caused by accidental arson, due to oversight or non-compliance with the rules of behavior with fire.

Nature of the fire

Fire in the forest is divided into three main groups - grassroots, underground, and overhead.

A ground fire spreads along the ground, covering the lower layers of forest vegetation: dried tree roots, shrubs, grass and moss cover, fallen dry leaves, but does not affect tree crowns.

In most cases, it is characteristic of deciduous forests. The fire speed is usually from 18 to 60 meters per hour, and with a strong fire, an area within a radius of 1 km is covered in one hour. The flame height can reach 2 m, and the combustion temperature at the edge will be 900 °C.

The classification of this type of fire is determined by:

• fluent burning characteristic of the spring period, when only the upper dry cover is covered;
• a stable, stronger fire that occurs in the second half of the summer season.

It is the stable grassroots fires that provoke crown forest and peat fires.

Crown fires occur during a long absence of precipitation and high air temperatures in summer. Most often they develop due to the large-scale spread of ground fire. Crown forest fires are typical for coniferous forests, dwarf cedar and shrub oak.

The minimum speed at which coniferous trees can be engulfed in fire is 6 km/h. Based on the type of crown fire, they can be divided into: stable and rapid burning. With a steady fire, all layers of trees burn, and with a fluent fire, the fire spreads through the crowns of plantings in jumps.

At the same time, the crown fire significantly outstrips the ground fire, thereby igniting new areas of the forest. After such a fire, partial or complete burning of the tree crown is observed.

occur during large-scale spread of ground and crown fires and spread through peat layers to a depth of more than 50 cm.

Due to the fact that peat can burn without oxygen, underground fires are difficult to detect. And the release of large volumes of smoke greatly pollutes the environment. As a result, the peat layers burn out, and underground voids form in their place.

An underground forest fire is the longest. The peat combustion process can take place even in winter under significant snow cover. Of all types of fires, peat fires are characterized by the slowest rate of progress, since this process is not affected by wind and changes in weather conditions.

Most often, this type of fire occurs in areas where peat deposits are developed when fire handling rules are not followed. Combustion can be triggered by lightning during dry thunderstorms. In addition, peat is characterized by spontaneous combustion at temperatures above 50 °C.

Classification

Forest fires are classified by assigning each fire its own category. The category group is influenced not only by its type, but also by the area covered by the flame and the number of people and equipment involved in extinguishing the fire.

There are six classes:

1. A - corresponds to damage to a burning area of ​​no more than 0.2 hectares, which can be extinguished by one person;
2. B - a small fire, not exceeding 2 hectares, is stopped by a group of 2-4 people;
3. B - classified as a small fire with an area of ​​2.1 to 20 hectares. 10 people will be involved in extinguishing;
4. G - medium fire, covers a forest area from 21 to 200 hectares. It can be stopped by specialized groups formed of 30-40 people;
5. D - large forest fire, the area of ​​the outbreak reaches 2000 hectares, extinguishing is carried out by a group of up to 100 people;
6. E - this category is determined by the forest burning area covering more than 2000 hectares. Catastrophic fire localizations are stopped by a strike group of 400 people.

Characteristics of the scale of spread of forest fires depend on many associated factors and are primarily determined by the forest area. In coniferous forests, where the main cover consists of mosses and lichens, fire flames spread rapidly. The more moist the soil floor is, the slower the fire spreads.

Changing the type of fire

Forest and peat fires, under the influence of strong gusts of wind, reaching open areas, are transferred to steppe territories. The classification of fire spread in the steppe corresponds to the ground forest combustion of soil floors.

At the same time, steppe landscape fires move faster and cover large areas in the shortest possible time. Steppe fires cause significant damage to flora and fauna, and also pose a danger to people and economic facilities.

The main source of fires in steppe landscapes is the anthropogenic factor. This also includes the controlled destruction of residual straw and dry grass after harvest. Natural causes of fires are quite rare.

Forecasting and estimation methods

The methods used to assess the likelihood of a landscape fire occurring make it possible to approximately determine the area and perimeter of the fire separately for each region. The initial data is taken from the values ​​of the forest fire coefficient and the approximate speed of flame propagation.

For people caught in a forest fire zone, the danger is associated with both direct exposure to the flame and possible poisoning with carbon monoxide and other harmful components produced during combustion. Therefore, when you go on vacation to the forest, do not forget that the main factor in forest fires is careless handling of fire.

Elimination stages

Fires are detected during forest patrols by ground and air transport. And the methods of extinguishing these fires depend on the class of fire.

But in the fight against forest fires, several main stages can be distinguished:

• forest fire reconnaissance. The boundaries of the fire, its type and speed of advance are being established. Based on the data obtained, an approximate fire extinguishing plan is drawn up;
• zone localization. This is the main and most labor-intensive process, which consists of stopping the advance of fire by laying barrier ditches;
• complete elimination of all residual foci;
• continuous bypass of the burned area in order to prevent re-ignition.

Fire- uncontrolled, unauthorized combustion of substances, materials and gas-air mixtures outside a special source, and causing significant material damage, injury to people on objects and rolling stock, which is divided into external and internal, open and hidden;

This is the combustion of substances, characterized by significant spread, high temperatures and duration, which poses a danger to people.

GOST 27331-87 dated 01/01/88 gives the following definition: “ fire- uncontrolled combustion outside a special fireplace, causing material damage.”

Under control You can understand not only process control, but also logging. Thus, a minute-by-minute burning of a residential building, by this definition, cannot be a fire, since it was controlled from the outside. Here you need to put the word uncontrollable.

Note:“At the same time, in this standard under fire is understood as a process characterized by social and/or economic damage as a result of the impact on people and/or material assets of thermal decomposition and/or combustion factors, developing outside a special focus, as well as the fire extinguishing agents used.”

ST SEV 383-87 « Fire“Uncontrolled combustion leading to damage.”

Law N 69-FZ dated December 21, 1994, GOST R 12.3.047-98 « Fire- uncontrolled combustion causing material damage, harm to the life and health of citizens, and the interests of society and the state.”

GOST 12.2.046-91“Fire is an uncontrolled combustion that develops in time and space.”

The most common causes of fires are:

careless handling of fire;

non-compliance with the rules of operation of production equipment;

spontaneous combustion of substances and materials;

static electricity discharges;

lightning discharges;

poor quality construction of buildings and structures;

neglect of safety rules;

Depending on the place of origin there are:

fires on vehicles;

steppe and field fires;

underground fires in mines and mines;

peat and forest fires;

fires in buildings and structures.

The latter, in turn, are divided into external(open), in which flames and smoke are clearly visible, and internal (closed), characterized by hidden paths of flame propagation.

The risk of fatalities from fires is approximately 8×10 – 5 people/year. The standard probability of fatalities in a fire is 10 – 6.

There are several stages in the development of a fire: initial, maximum development And attenuation.

The area covered by fires is conventionally divided into 3 zones - active combustion(fire source) thermal effects from fumes.

External signs of an active combustion zone are the presence of flames, as well as smoldering or hot materials.

The main characteristic of the destructive effect of a fire is the temperature that develops during combustion. For residential buildings and public buildings, indoor temperatures reach 800-900 °C. As a rule, the highest temperatures occur during external fires and on average are 1200-1350 °C for flammable gases, 1100-1300 °C for liquids, and 1000-1250 °C for solids. When burning thermite, electron, magnesium, the maximum temperature reaches 2000-3000 °C.

The space around the combustion zone, in which the temperature as a result of heat exchange reaches values ​​that cause a destructive effect on surrounding objects and are dangerous to humans, is called the thermal impact zone. It is generally accepted that the thermal impact zone surrounding the combustion zone includes an area where the temperature of the mixture of air and gaseous combustion products is not less than 60-80 °C.

During a fire, significant movements of air and combustion products occur. The heated combustion gases rush upward, causing an influx of denser cold air into the combustion zone. During fires inside buildings, the intensity of gas exchange depends on the size and location of openings in walls and ceilings, the height of the premises, as well as the quantity and properties of burning materials. The direction of movement of heated products usually determines the likely paths of fire propagation, since powerful ascending heat flows can carry sparks, burning coals and brands over a considerable distance, creating new sources of combustion. Combustion products (smoke) released during a fire form a smoke zone. The composition of smoke usually includes nitrogen, oxygen, carbon monoxide, carbon dioxide, water vapor, as well as ash and other substances. Many products of complete and incomplete combustion that make up smoke have increased toxicity, especially toxic products formed during the combustion of polymers. In some cases, products of incomplete combustion, such as carbon monoxide, can form flammable and explosive mixtures with oxygen.

Depending on the conditions of their occurrence and development. In order to study fires in detail and develop tactics to combat them, all fires are classified into groups, classes and types. According to the conditions of gas and heat exchange with the environment, fires are divided into 2 large groups - in open space and in fences.

Fires in open space can be divided into 3 types:

• spreading;
• non-proliferating (local);

Spreading- fires with increasing sizes (width fire front , fire perimeter, radius, length of fire flanks, etc.). Fires in open space spread in different directions and at different speeds depending on heat exchange conditions, magnitude fire breaks , sizes torches flame , critical heat flows , causing fire materials, and other factors. The predominant direction of propagation of the main fire front is formed depending on the distribution flammable materials or objects on the area, as well as on environmental parameters (wind direction and speed). The boundaries of a fire are formed during its development and depend on the factors listed above.

Non-propagating (local)- fires in which the size remains unchanged. A local fire is a special case of a spreading fire, when the ignition of objects surrounding the fire from radiant heat is excluded. In these conditions, meteorological parameters apply. So, for example, from a sufficiently powerful fire source, fire can spread as a result of the transfer sparks and firebrands towards non-burning objects in the direction of the wind. This mechanism is typical for large fires in timber warehouses, in rural areas, in open warehouses of various materials, in urban areas with narrow streets. In large oil and petroleum products warehouses, a fire in one or a group of tanks is classified as non-propagating. However, under certain conditions, fires at oil depots develop into spreading fires. Spread of combustion damage to neighboring tanks can occur due to emissions of burning petroleum products and deformation of metal tanks.

The classification of fires based on their spread is closely related to the time of their development. Mass fire can occur in large areas of warehouses of solid and liquid combustible materials, in forests, rural settlements and workers' settlements, built up with buildings with low resistance to fire.

There are two types of fires in fences: open and closed. Open fires characteristically free burnout combustible materials without transition to explosion (flash ). These fires develop with fully or partially open openings (limited ventilation ). They are characterized by a high rate of spread combustion with a predominant direction towards open openings and throwing a torch through them flame , as a result of which there is a threat of fire spreading to the upper floors and to neighboring buildings (structures). In open fires burn rate materials depends on their physical and chemical properties, distribution in the volume of the room and gas exchange conditions.

Open fires are divided into 2 groups. The first group includes fires in rooms up to 6 m high, in which window openings are located at the same level and gas exchange occurs within these openings through a common equivalent opening (residential premises, schools, hospitals, administrative and similar premises). The second group includes fires in rooms with a height of more than 6 m, in which the openings in the fences are located at different levels, and the distances between the centers of the supply and exhaust openings can be very significant. In these rooms and parts of the building there are large pressure differences in height and, consequently, high gas flow rates, as well as burnout rates fire load . Such premises include machine and technological rooms of industrial buildings, auditorium and stage complexes of theaters, etc. Closed fires occur with completely closed openings, when gas exchange occurs only due to the infiltration of air and gases removed from the combustion zone through leaks in fences, door vestibules, window frames, with existing natural exhaust ventilation systems without organized air flow, as well as in the absence of exhaust ventilation systems.

It has been experimentally established that when closed fires(indoors) the burnout rate of the most common combustible materials does not depend on their physical and chemical properties, distribution in the volume of the room and is completely limited by the air flow entering through cracks and loose connections of windows and doors. The exception is particularly dangerous oxygen-containing flammable materials (celluloid, gunpowder, etc.), as well as some synthetic polymer materials containing highly volatile components. The burnout rate of such substances and materials is very high and can occur either without access oxygen, or with limited access. Closed fires are characterized by the danger of the fire transitioning into an explosion (flash) with an increase in the flow of air into the room after a period of fire in conditions of limited air access, as well as the danger of destruction of building structures when their limits are exceeded fire resistance . (Cm. Fire resistance limit of a building structure) . At the same time fire fighting indoors is easier to achieve due to the possibility of using a highly effective volumetric fire extinguishing method. Closed fires can be divided into 3 groups:

• in rooms with glazed window openings (residential and public buildings);
• in rooms with doorways without glazing (warehouse and industrial premises, garages, etc.);
• in closed volumes without window openings (basements of industrial buildings, refrigerator chambers, some material warehouses, holds, elevators, lightless buildings of industrial enterprises).

In each group, the fire load can be concentrated or dispersed in layers of different heights and density of distribution of materials.

The choice of fire depends on the type of fire, determined by the properties of combustible substances and materials. ways And fire extinguishing agents . Thus, when burning metals and metal-containing substances, the most acceptable fire extinguishing agents are fire extinguishing powders, and in case of fires, spills LVZH And GJ The main extinguishing agent is foam.

Lit.:

Fire is an uncontrolled fire that causes material damage, as well as harm to people, their property or nature. The most common causes of its occurrence are neglect of the rules for operating electrical appliances and careless handling of fire.

Types of fires

There are 6 main varieties:

The latter is divided into three types. When open, fire and smoke are clearly visible. An internal fire is characterized by hidden ways of spreading the flame - that is why it is also called hidden.

Classification of fires by type combines types of fire according to the objects where the fire occurred. The industrial type of fire includes fires in factories, factories and warehouses. In turn, this means uncontrolled fire in the forest, steppe, peat bogs, as well as landscape burning. Thus, combustion in a residential building or at an object of cultural and social significance is classified as a household fire.

Depending on the level, a certain number of equipment and rescuers are sent to the call. In order to simplify the classification, a conditional sign of complexity was introduced - rank. In large branches there are six calls:

• No. 1: 2 departments on tankers are working at the scene of the fire and have begun liquidation;
• No. 1-BIS: there are not enough forces and equipment, reinforcements are needed - 2 more squads come to the rescue (4 in total at the fire site);
• No. 2: the fire has engulfed a large area and continues to grow - as a result, there are already 6 departments at the facility extinguishing the flames at the same time;
• No. 3: difficult situation at the site, lack of people, equipment, water sources - 10 departments are working together on the fire;
• No. 4: the situation is similar to call 2, 13 branches are involved in the liquidation;
• No. 5: Flames are getting out of control, with 15 departments on the scene.

In smaller garrisons there may be 3-5 call numbers. It is worth noting that there is a so-called zero danger level - a false report of a fire.

Classification of fires in the Russian Federation

The 8th article of the “Technical Regulations on Fire Safety Requirements” describes in detail the following combustion classes. Thus, fire “A” refers to the ignition of solid substances and materials, and fire “B” refers to flammable liquids and melting substances. In turn, groups “C” and “D” are represented by the combustion of gases and metals, respectively.

Class “E” fire refers to substances and materials of electrical installations that are engulfed in flames and are energized. According to this classification, the most dangerous is “F”, that is, the fire of nuclear material, radioactive substance or waste.

It is worth noting that the above document is supplemented by state standard 27331, which introduces subclasses for A-D. Thus, the designations A1 and A2 mean the combustion of solids with and without smoldering. In turn, subclasses B1 and B2 divided substances into water-soluble and water-insoluble.

The group of metals received three additional designations. D1 refers to the ignition of light metals. However, alkali metals and other metals with similar properties are classified as D2. Code D3 means ignition of metal-containing compounds.

Fire characteristics

High temperature during a fire causes the greatest destruction and is therefore considered its main characteristic. During a fire in a room, it is 850 degrees Celsius. The highest indicators are for external fires of flammable gases - 1200-1350 degrees. However, when thermite, magnesium and other similar substances ignite, the maximum temperature can reach 3000 degrees.

Despite this, the death of the vast majority of fire victims is caused by combustion products. The fact is that they are represented by toxic substances, which lead to death. Products of incomplete combustion are especially dangerous, as they can form a flammable or explosive mixture with oxygen.

Let's sum it up

A fire is an uncontrolled flame that causes harm to people or their property. For their more effective elimination, they were divided into types and classifications.

A special ranking system was also created, which determines the complexity of the fire and the number of equipment and people needed to extinguish it. It is worth noting that the list of calls may vary depending on the size of the fire garrison.

Although high temperatures cause most of the destruction, the main task of firefighters is to preserve the life and health of people in danger as much as possible. Therefore, they use different equipment, the list of which is strictly defined for each fire class. This prevents the formation of mixtures of incomplete combustion products that are dangerous to humans.

All fires, depending on how they arise, and also taking into account their development paths, have an extensive classification. Dividing fires into types is extremely important for developing competent tactics for their prevention and elimination.

According to the type of substances involved in the combustion process, fires are classified as follows:

1. Combustion of solids. These are, as a rule, flammable wood, rubber objects, and textiles.
2. Gaseous substances. All natural or industrial flammable gases can not only ignite, but also cause an explosion.
3. Liquid substances. These include flammable mixtures such as diesel fuel, oil and its derivatives, resin, and alcohol-containing liquids.
4. A fire can also occur with the participation of electric current. In this type of fire, it does not matter what role the electric current plays: passive or active.
5. Combustion involving metals with low density. These are the so-called light metals - titanium, lithium, magnesium, as well as alloys made from them.

Fires in fences and open areas

Based on their interaction with the environment, two broad groups of fires can be distinguished. These are fires that occur in fences and open areas. The latter have the following classification:

Massive

Characteristic of large open areas, including natural areas. It has a high speed of spread. It can cover entire settlements, especially with dense buildings.

Spreading

With this type, the width of the fire front and its perimeter are constantly increasing. They can have different directions, moving at non-uniform speeds. This is due to the materials involved in the fire, the size of the flame itself and the conditions under which heat exchange occurs. The presence of wind, its speed and direction have a great influence. The boundaries of the spreading type of fire are established during the formation of the main front.

Local or non-propagating

The main characteristic is the invariability of their sizes. It is part of a spreading fire, but is considered an isolated incident. Occurs in meteorological conditions when ignition of the environment from the temperature of a local fire is excluded. Such a fire can occur when sparks fall on poorly burning objects. In oil warehouses, a fire in one tank is considered local until, under unfavorable conditions, it develops into the variant described above.

Open and closed fires in enclosure conditions

In open fires The combustion process occurs freely and smoothly. They are not characterized by explosive reactions with flashes. They move quickly in the direction of drafts. They strive for openings or cracks in the structure. Subsequently, through them, the flame can spread to nearby buildings or neighboring territory.

The speed at which the combustion process will occur depends on the area of ​​the building, the existing conditions for the exchange of gases with the environment and the properties of the burning materials.

Fire in open areas is divided into 2 main groups:

• Occurring in buildings with a ceiling height of less than 6 m, in which all windows are on the same level. All secondary educational institutions, apartment buildings, and medical buildings fit this description.
• Occurring in buildings with ceiling heights of more than 6 m. Windows are designed at different levels. These are structures such as factory or repair shops, auditoriums in palaces of culture or theaters.

Closed types of fires occur under conditions of minimal air flow. All openings are closed, ventilation hatches are missing or tightly closed. Practice shows that in closed buildings the burnout process is not associated with the chemical or physical properties of combustible substances. It is completely controlled by the volume of air that enters through existing cracks in walls or leaking doorways.

The only exceptions can be flammable materials containing oxygen. This is gunpowder, some types of polymer. They have a high burnout rate, and for this they do not need oxygen at all. Closed fires are dangerous because a sharp increase in air flow can lead to an explosion. However, it is easier to extinguish a fire indoors by using an effective extinguishing method and using a sufficient amount of extinguishing agents.

Based on the type of building in which the fire started, closed fires are divided into 3 groups:

• Occurring in buildings that do not have windows or glass openings. These are warehouses, garages, workshops.
• Appearing in rooms where there are door and window openings (residential buildings, public institutions)
• A closed fire can occur in completely enclosed areas (refrigeration chambers, hatches, holds, industrial basements).

Classifying fires is important for developing more effective fire suppression methods. Studying flammable substances in fire conditions provides information that helps to use the most appropriate extinguishing agent (foam, powder).

Types of fires by building density

Fires are also classified based on the percentage of development. For dense infrastructure, the following categories are distinguished:

1. Separate fire, arising in a specific free-standing structure. The movement of people through such a territory is permitted without the use of special protective equipment, since thermal radiation does not cause harm.
2. Complete fire, in which intense fire covers a larger number of all buildings in a given territorial area. In a situation where there is a massive fire, people cannot move freely without protection.
3. Firestorm. The most dangerous and destructive type. It has a high flame, accompanied by whirlwinds of hot air with fiery sparks. The air flow reaches 50 km/h.
4. Mass or combined option. Includes fires of separate and continuous types.

Fires on vehicles

They depend on the type of transport: overground, underground, water, underwater, air, including space or special. Statistics show that the rate of human casualties in overground transport alone is 200 annually.

The main risk factors for fire are:

1. Smoking.
2. Faulty electrical wiring (for example, speakers or lighting fixtures with incorrect wiring).
3. Deliberate arson.

The presence of a large number of plastic surfaces makes a modern car unsafe. If the driver understands that the resources of the fire extinguisher will not be enough to extinguish the fire on his own, he should immediately disembark the passengers and instruct them to go to a safe distance, then leave the car themselves. Immediately after this, inform the fire department.

Vehicle fires are particularly dangerous when they occur on board an aircraft. The task of the crew team will be to act to prevent a local type of fire (inside the fuselage, in the power plant or chassis) and prevent its spread.

Fires in nature: their types and characteristics

An instantly changing situation characterizes such a type of fire as landscape, which includes steppe and field fires. Burning dry grass is a source of concentration of combustion products and high temperature. A person caught in such a fire can receive burns of varying degrees, leading to death in the most tragic cases. Illuminated panicles of grass are carried by the wind over long distances and cause the fire to quickly spread not only to steppe territories. It is possible to escape in this situation; you need to find the burned-out space and protect the respiratory organs with a bandage of clothing. If possible, the bandage should be wet.

In local cases, fire fighting is carried out by squeezing the burning edge with any suitable object: for example, non-synthetic clothing soaked in water, a shovel. quickly acquire the character of a mass fire, to extinguish which all nearby fire departments are involved, a headquarters is organized, and a large collection of forces and resources may follow to analyze information from all areas where open burning occurs. Local water sources are used, counter annealing strips are laid, soil is backfilled, and guards are installed for a certain time.

Depending on their location, forest fires are:

Grassroots

Distributes only at the bottom of the forest. Affects moss, soil, exposed tree roots. Doesn't cause much harm. They can have a fluent and stable form of development. The resistant type is typical for arid areas. This species goes deep into the soil and is difficult to eradicate. They are characterized by a low flame and a small width of the fiery edge.

Running fires usually cover areas with grass and lichens. They tend to jump from one area to another. The maximum height of the fire can reach 3.5 m. The resulting deposits on the trunks lead to 20% of the death of the tree. They cause more damage to the forest.

Horse

Such species are common in forests dominated by fir, pine and spruce. As a rule, they start from ground fires. They spread to the tops of trees, completely destroying the crown. This type of fire spreads quickly. The tree stand can burn out completely with damage to the root system.

Peat (soil)

Underground, the most stable, capable of smoldering for several years. Their favorite places are peat bogs, dried sphagnum bogs or places where the soil is rich in peat. With such a fire, the flame is not always visible. Underground burning of voids with constant acrid smoke are the main signs of such forest fires.

The current GOST R22.109-99 qualifies peat and forest fires as standard and large.

The height of the flames of ground running fires can be up to 3.5 m in height and the speed of coverage is up to 3 meters per minute. During periods of prolonged absence of rain, ground fires can occur that have the following properties:

• rain resistance;
• small width of the fire edge;
• fire height up to 70 cm;
• spreading speed up to 80 cm/min.

Fires in coniferous forests are more often classified as burning fires. They can be destructive because the resin of coniferous trees makes them defenseless against flames.

Peat fires, most often underground, have a spread speed of 10 cm to 10 meters per day and can continue for many years, therefore they require special measures to eliminate the sources of spread. From digging to the use of special extinguishing technologies, when jets of water are supplied to the soil under high pressure through special devices. Such devices are fire nozzles for extinguishing peat fires.

The peculiarity of underground fires is that they can last from one day to several years.

The causes of occurrence are:

• External (friction of parts of conveyor belt mechanisms, ropes, welding, blasting operations in violation of safety regulations, damage to electrical equipment, etc.).
• Internal (spontaneous combustion of rocks when oxygen enters when air enters the open surfaces of the shale, poor ventilation, etc.).

The fight against such a phenomenon as underground fires in mines and mines is carried out by paramilitary mine rescue units by planning optimal schemes for opening deposits for their subsequent isolation and flooding. When drawing up diagrams, the size of the flames and the directions of heat flows are taken into account, as well as the type of disaster: open or closed nature of the fire.

When performing the process of localizing closed (endogenous in this case) fires, filling the shaft (mine) with non-flammable gases or vapor-gas mixtures is often used to prevent explosions. In case of open types of fires (exogenous), water and chemical fire extinguishing agents are used.

Man-made fires

Disasters in the form of fires as a result of extensive human action are considered man-made fires, divided into several categories:

1. Enterprises, warehouses, pipelines associated with the processing and transportation of oil and flammable chemicals are designated A.
2. Shops for the processing and transportation of coal dust associated with the storage and production of flour, powdered sugar, and wood flour are designated B.
3. Sawmills, furniture and carpentry production and everything related to this field of activity are designated by the letter B.
4. Warehouses and production of non-combustible materials in molten form, enterprises whose activities are related to the combustion of various types of fuel have the letter G.
5. Companies whose activities are related to cold storage of non-flammable products are indexed as D.

The consequences of man-made disasters can include strong thermal radiation, building collapses, toxic damage to the respiratory system, and impacts on the health of people with systemic diseases.

Preventive measures in these cases can include special recommendations on compliance with the work regime, competent activities of the supervisory and preventive service, and professionally developed fire extinguishing tactics.

Fires in buildings and structures

Annual statistics on fires in the residential sector are 75-80% of the total volume of all types of fires. Added to these are fires in offices and small industries. There are many reasons for this: from faulty electrical wiring and non-compliance with the rules for operating household and industrial equipment to deliberate arson. Such disasters are classified as spreading, non-spreading and widespread.

Spreading fires in buildings and structures are characterized by a rapid increase in the perimeter, radius, and width of the front.

The typology of open fires is determined by:

• combustion of flammable substances without explosion;
• physical and chemical characteristics of stored and used substances;
• gas exchange conditions in the room.

Since buildings come with window openings located on the same level and openings at different levels, the movement of gas flows and the rate of burnout are different. The second type of premises may include workshops of industrial enterprises, sports complexes, theaters and the like.

The rate of spread and burnout during closed fires is determined by the total volume of the building and the presence of natural air circulation in it. In the presence of explosive objects and substances, the situation becomes more complicated.

Fire investigations

In each case of fire, investigative actions are carried out. It is recommended not to delay the inspection.

Among the methods of inspecting the site of a fire are:

• linear– from the established location directly along the propagation front;
• concentric– directed from the central point to the peripheral ones;
• eccentric– its direction is opposite to the previous one;
• nodal– inspection is carried out from important damage to minor ones.

The inspection is carried out to determine the technical causes of the fire. Specialists record the physical conditions of the area being examined, visually identify the suspected source of fire, look for material evidence and collect other information.

Literature used in preparing the material:

• Combustion-fire-explosion-safety. Baratov A.N. Moscow, 2003.
• Kimstach I.F., Devlishev P.P., Evtyushkin N.M. Fire tactics. Moscow, 1984.