What factors determine the risk of electric shock to a person? Ensuring safety during the operation of electrical installations and protection from the adverse effects of electricity are factors that determine the danger of electric shock.
The outcome of electric shock depends on the following factors: the electrical resistance of the human body, the strength of the current flowing through the body, the time of exposure to the current, the path of the current, the frequency and type of current, the individual characteristics of the human body, external (environmental) conditions and other factors.
The amount of current flowing through the human body depends on the touch voltage U and resistance of the human body R.
The resistance of the human body is a nonlinear value, depending on many factors: skin resistance and its condition; on the magnitude of the current and applied voltage; on the duration of current flow.
The upper stratum corneum of the skin has the greatest resistance. In a dry and uncontaminated state, it can be considered as a dielectric: the resistivity of the stratum corneum reaches 10 5 -10 6 Ohm * m, which is thousands of times higher than the resistance of other layers of the skin.
The resistance of the human body with dry, clean and intact skin ranges from 1000 to 100,000 Ohms, and the resistance of the body layers is only 500-700 Ohms.
As a calculated value for alternating current of industrial frequency, the resistance of the human body (R 4 ) is taken equal to 1000 Ohm. In real conditions, the resistance of the human body is not a constant value and depends on a number of factors.
As the current passing through the human body increases, its resistance decreases, as this increases the heating of the skin and sweating. For the same reason, it decreases R 4 with increasing duration of current flow. The higher the applied voltage, the greater the human current/h, the faster the human skin resistance decreases.
With increasing tension, the resistance of the skin decreases tens of times, and consequently, the resistance of the body as a whole decreases; it approaches the resistance of the internal tissues of the body, i.e., to its lowest value (300-500 Ohms). This can be explained by electrical breakdown of the skin layer, which occurs at a voltage of 50-200 V.
Contamination of the skin with various substances, especially those that conduct electric current well (metal or coal dust, scale, etc.), reduces its resistance.
The main damaging factor of electric current is the strength of the current passing through the human body. Small currents only cause discomfort. At currents greater than 10-15 mA, a person is not able to independently free himself from live parts and the effect of the current becomes prolonged (non-releasing current). At a current of 20-25 mA (50 Hz), a person begins to experience difficulty breathing, which intensifies with increasing current. When exposed to such a current, suffocation occurs within a few minutes. With prolonged exposure to currents of several tens of milliamps and an action time of 15-20 s, respiratory paralysis and death can occur. Currents of 50-80 mA lead to cardiac fibrillation, which consists of random contraction and relaxation of the muscle fibers of the heart, as a result of which blood circulation stops and the heart stops. The action of a current of 100 mA for 2-3 s leads to death (lethal current).
At low voltages (up to 100 V), direct current is approximately 3-4 times less dangerous than alternating current with a frequency of 50 Hz; at voltages of 400-500 V their danger is comparable, and at higher voltages direct current is even more dangerous than alternating current.
The most dangerous current is industrial frequency (20--100 Hz). The reduction in the danger of the action of current on a living organism is noticeably affected at a frequency of 1000 Hz and above. High-frequency currents, ranging from hundreds of kilohertz, cause only burns and do not damage internal organs. This is explained by the fact that such currents are not capable of causing excitation of nerve and muscle tissue.
The path of electrical current through the human body plays a significant role in the outcome of the injury. The danger of electric shock increases greatly when it passes through vital organs: the heart, lungs, and brain. However, the reflex effect of current on them also occurs through other paths of its passage, although the danger of injury is sharply reduced. The most dangerous such paths include the “head-arms” and “head-legs” loops, and the least dangerous are the “leg-leg” loops. However, fatal injuries are known when the current passed along the leg-to-leg or arm-to-arm path.
A person's mental and physical condition also influences the severity of an electric shock. In case of diseases of the heart, thyroid gland, etc., a person is more severely damaged at lower current values, since in this case the electrical resistance of the human body and the general resistance of the body to external irritations decrease. It has been noted, for example, that for women the threshold current values are approximately 1.5 times lower than for men. This is explained by the weaker physical development of women. When using alcoholic beverages, the resistance of the human body drops, the human body's resistance and attention decrease. With concentrated attention, the body's resistance increases.
The outcome of electric shock is influenced by environmental conditions (temperature, humidity) and the surrounding environment (the presence of conductive dust, caustic vapors and gases). Increased temperature and humidity increase the risk of electric shock. The lower the atmospheric pressure, the higher the risk of injury. Dampness, caustic vapors and gases have a destructive effect on the insulation of electrical installations.
Electrical installations are classified by voltage: with a rated voltage of up to 1000 V and over 1000 V. The safety of servicing electrical equipment also depends on environmental factors.
Depending on the presence of conditions that increase the danger of exposure to current on a person, all premises according to the danger of electric shock to people are divided into the following classes:
- * first - premises without increased danger, in which there are no conditions that create increased and special danger;
- * second - premises with increased danger, characterized by the presence in them of at least one of the listed signs: dampness (relative air humidity exceeds 75% for a long time); high temperature (above + 35 °C); conductive dust; conductive floors; the possibility of simultaneous human contact with metal structures of buildings connected to the ground, on the one hand, and metal housings of electrical equipment, on the other;
- * third - particularly dangerous premises, characterized by the following characteristics: relative air humidity close to 100% (visually determined by the presence of condensation on the inner surface of building structures of buildings and premises); chemically aggressive environment; the presence of two or more signs of high-risk premises at the same time; as well as the areas where external electrical installations are located. According to the method of protecting a person from electric shock, electrical products are divided into five classes: 0, 01.1, II, III.
Class 0 includes products with a rated voltage of more than 42 V with working insulation and without devices for grounding. Household appliances are manufactured according to class 0, since they are designed to work in rooms without increased danger.
Class 01 includes products with working insulation and a grounding element. The wire for connection to the power source does not have a grounding conductor.
Class I includes products with working insulation, an element for grounding and a power wire with a grounding (grounding) conductor and a plug with a grounding contact.
Class P includes products that have all parts accessible to touch with double or reinforced insulation relative to normally live parts and do not have grounding elements.
Class III represents products without internal and external electrical circuits with a voltage not exceeding 42 V.
The degree of harmful effects of electric current on a person when he is damaged depends on: - individual characteristics of the body; - general electrical resistance of the body (conductivity); - voltage and type of current; - paths of current passage through the human body; - duration of exposure; - environmental conditions (temperature, humidity, dust) and other factors.
Individual characteristics people largely determine the outcome of the defeat. A current that causes only weak sensations in one person may be persistent for another.
Non-releasing current is an electric current that, when passing through a person, causes irresistible convulsive contractions of the muscles of the arm in which the conductor is clamped.
The nature of the effect at the same current value depends on the state of the nervous system and the entire organism as a whole, as well as on the mass of the person and his physical development. The manifestation of the individual characteristics of the human body is expressed in the physical and mental state of the body:
High or low activity; - degree of concentration; - lack of will, fatigue, alcohol intoxication; - weakening of the body due to illness. As the body's vitality decreases, the risk of electric shock increases.
Total electrical resistance The human body is made up of the resistance of parts of the body located in the path of the current. The main resistance in the current circuit through the human body is the upper stratum corneum of the skin. The resistance of the human body varies widely and depends on: - the condition of the skin (dry, wet, clean, damaged, etc.); - contact density; - contact area; - the magnitude of the current through a person and the applied voltage; - current frequency; - time of exposure to current on a person.
Due to the large differences in the resistance values of human tissues and the impossibility of predicting in advance the place of contact of the human body with a live part of the equipment, it is impossible to determine the damaging value of the current. Therefore, to assess safe conditions, the permissible voltage is used.
Safety voltage (low voltage)- this is a rated voltage of not more than 42V, used to reduce the risk of electric shock. However, taking into account the requirements of the International Electrotechnical Committee (IEC), the concept of safe voltage is clarified as ultra-low (small) voltage . It is a voltage not exceeding 50V AC and 120V DC.
It has been established that alternating current with a frequency of 50-60 Hz is more dangerous than direct current. This also follows from Table 1, since the same effects are caused by larger values of direct current than alternating current. However, even a small direct current, below the threshold of sensation, with a rapid break in the circuit, gives very sharp shocks, sometimes causing cramps in the arm muscles. Path, through which electric current passes through the human body, largely determines the degree of damage to the body. The following options for directions of current movement through the human body are possible: - a person touches live wires (parts of equipment) with both hands, in this case the direction of current movement appears from one hand to the other, that is "hand - hand";- when one hand touches the source, the current path is closed through both legs to the ground "arm - legs";- when the insulation of current-carrying parts of the equipment breaks down on the body, the worker’s hands become energized, at the same time, the flow of current from the equipment body to the ground leads to the fact that the legs also become energized, but with a different potential, so a current path arises "hands-legs";
When current flows into the ground from faulty electrical equipment, the ground nearby receives a changing voltage potential, and a person who steps on such ground with both feet finds himself under a potential difference, that is, each of his legs receives a different voltage potential, resulting in a step voltage and an electrical circuit "leg - leg";- touching live parts with your head can cause, depending on the nature of the work performed, a path of current to your hands or feet - "head - hands", "head - feet".
The listed options for the passage of current through the human body are not exhaustive. There have been cases when the current passed through the body along other paths: “back - arms”, “shoulder - hand”, etc. All options differ in the degree of danger.
The most dangerous options are “head - hands”, “head - feet”, “hands - feet”. This is explained by the fact that vital systems of the body - the brain, the heart - fall into the affected area.
Duration of current exposure. The shorter the duration of exposure to current, the less the danger to the human body. If the current does not go away, but does not yet cause breathing or heart problems, then a quick shutdown saves the victim, who would not be able to free himself. Probability of occurrence fibrillation, as well as cardiac arrest depends on the duration of the current.
Heart fibrillation- this is a multi-temporal and scattered contraction of individual fibers of the heart muscle, unable to support it effective work and does not go away on its own (without vigorous therapeutic measures).
With prolonged exposure to current, the resistance of the human body drops and the current increases to a value that can cause respiratory arrest or even cardiac fibrillation. Stopping breathing does not occur instantly, but after a few seconds, and the more current passes through a person, the shorter this time. Timely disconnection of the victim helps prevent paralysis of the respiratory muscles.
Environmental conditions, surrounding a person during work activities may increase the risk of electric shock. For example, working in hot and damp rooms with high energy consumption leads to increased sweating and a decrease in the resistance of the surface layer of the skin. The cramped nature of the premises increases the likelihood of accidental contact with live parts of the equipment. Metal or other conductive floors also create an increased electrical hazard.
Related information.
1. Current value – the main factor characterizing the severity of electrical injury. IN Appendix M information is provided on the effect of currents of different magnitudes on the human body. To characterize this influence, threshold values are used:
- sensitivity threshold- the minimum current strength that a person feels. It is 0.6...1.5 mA for alternating current (frequency 50 Hz) and 5...7 mA for direct current. This current is safe for humans;
- threshold non-releasing current– the minimum current strength at which a person cannot independently remove his hands from live parts. In terms of magnitude, such a current is not dangerous to humans, but with prolonged exposure it can lead to serious consequences and even death. With direct current, a person can independently tear his hand off the conductor at any current strength, but at the moment of separation, painful muscle contractions occur, similar to those that occur with alternating current. A person is able to withstand pain when separated from live parts at a current strength of no more than 50 - 80 mA.
- threshold fibrillation current– the minimum current strength at which fibrillation of the victim’s cardiac activity occurs. Causes death of the victim if the current travel time exceeds 1 s, is 100 mA for alternating current at 50 Hz and 300 mA for direct current. A current of more than 5 A causes immediate cardiac arrest, bypassing the state of fibrillation.
- maximum permissible current– the maximum current strength that does not cause electrical injury for any duration of action.
2.Type and frequency of current – the resistance of the human body has a capacitive component, therefore a change in the frequency of the applied voltage leads to a change in the total resistance of the body and an increase in the strength of the passing current.
Increasing the current frequency from 0 to 200 Hz leads to an increase in the risk of injury. At current frequencies of 100 kHz and above, there is only a danger of burns. Further increases in frequency reduce the danger of alternating current, which disappears altogether at a frequency of 450 kHz. At voltages up to 500 V, direct current is safer (4-5 times), above 500 V, direct current is more dangerous. The most dangerous for humans is alternating current with a frequency of 50 Hz at a voltage of 220 V. The approximate values of the limit values for such current are given in table. 6.1
Table 6.1. Threshold values of alternating current frequency 50 Hz
3. Electrical resistance of the human body is determined by the resistance of the stratum corneum of the skin and depends on the applied voltage. Dry, intact skin has a resistance of 500...500,000 Ohms. Moist, contaminated skin has significantly less resistance, which is due to the passage of current through the sweat glands and subcutaneous area. The resistance of the human body to alternating current of frequency 50 Hz is taken equal to 1,000 Ohms.
A living organism consists of various cells and salt solutions, which causes different electrical resistance of different parts of the body. In addition, skin resistance in different places The human body is very different, so the severity of electrical injury depends not least on the location of the injury. The attention factor increases the resistance of the human body and reduces the likelihood of defeat. It is known that about 85% of electrical injuries occur at the end of the work shift due to weakening workers' attention.
4.Current duration – when current passes, the skin resistance sharply decreases, which leads to more severe electrical injuries: after 30 s, the body resistance decreases by 25%, and after 90 s – by 70%. In table 6.2 shows the dependence of the maximum permissible current on the duration of its action.
Table 6.2 – Maximum permissible current values (~50 Hz)
In addition, the effects of current exposure accumulate in the body and the probability of the moment of current passage coinciding with the vulnerable T-phase of the cardiac cycle increases (with a period of 0.15 - 0.20 s, during which the contraction of the ventricles of the heart ends and they go into a relaxed state) . That is why, when providing assistance, firstly, you need to stop the current.
5.Direction of current flow – if vital organs (heart, lungs, brain) are in the path of the current, then the danger of damage is very high. In other directions of current flow, the severity of the injury is significantly reduced. In practice, there are 15 possible paths for the passage of current in the human body, the most common of which are the “arm – arm” (40% of cases) and “right arm – legs” (20% of cases) directions. The most dangerous paths are “head–hands” and “head–legs,” which are rarely implemented in practice. The least dangerous is the “leg-to-leg” path (lower loop), which occurs when a person is exposed to the tension of a step.
6.Connection diagram into an electrical circuit - a person can simultaneously touch two phase wires of an alternating current network (two-phase touch), one phase wire (single-phase touch), approach a dangerous distance to non-insulated live parts, touch the body of electrical equipment that is energized, or enter the area action of step voltage.
5.Individual properties of a person – physically healthy people tolerate electric shocks more easily than sick and weak people. The least resistant to electric current are people with nervous diseases, diseases of the skin, cardiovascular system, internal secretion organs, and lungs. Physical and emotional stress increases the risk of electric shock to a person.
electrical safety
Electric current is the ordered movement of charged particles. The main causes of electric shock: 1) violation of insulation or loss of its insulating properties, 2) direct contact or dangerous approach to live parts that are energized, 3) inconsistency of actions.
Electric current has the following effects on humans:
1. thermal (heating and tissue burns),
2. electrolytic (decomposition of blood and liquid components),
3. biological (excitation of living tissues of the body, causing convulsive contractions and disruption of biological processes).
Types of electrical damage
All electrical injuries are divided into two groups:
1. local electrical injuries - clearly expressed local tissue damage;
come in the following forms:
· electrical burn,
· electrical signs,
· metallization of the skin,
· mechanical damage,
Electroophthalmia (eye damage from an electric arc).
2. general electrical injuries - excitation of living tissues of the body, accompanied by convulsive muscle contractions.
convulsive contraction without loss of consciousness (I degree of danger),
· with loss of consciousness, but with preservation of breathing and blood circulation (II degree of danger),
loss of consciousness, disturbance of cardiac activity, breathing or both (III degree),
· clinical death, lasts 4-5 minutes (IV degree).
Factors influencing the risk of electric shock to humans
The main factors influencing the outcome of electrical injury are the following:
· current strength, I;
· voltage, U;
· resistance of the human body, R h;
· duration of exposure;
· path, type and frequency of current;
individual characteristics of a person;
· environmental conditions.
One of the main factors is the current strength. To characterize the impact, 3 threshold values have been established:
1. Threshold perceptible - the minimum value of current that causes pain.
2. Threshold non-releasing - the minimum current value at which a person cannot free himself from the current-carrying part.
3. Threshold fibrillation - the minimum current value at which the heart rhythm is disrupted.
The resistance of the human body consists of the resistance of the skin and internal organs. Intact, dry and clean skin has a resistance of 2kOhm to 2MOhm. For calculations, human resistance is assumed to be 1000 Ohms. Nerve fibers provide 25% of the resistance of internal organs. Striking current=1.2*(30+3.7G p) mA, where G p is the human body mass.
The duration of exposure affects the outcome of the lesion, because Over time, due to moisturizing of the skin, the resistance of the human body decreases and the current flowing through the human body increases.
Type of current: alternating current with a frequency of 50-60 Hz is more dangerous than direct current, however, at voltages above 300 V, the danger of direct current increases, because A large direct current when the circuit breaks gives very sharp shocks.
Current path:
Rice. 1. Characteristic current paths in the human body (current loops)
1 – hand – hand; 2 – right hand – legs; 3 – left hand – legs; 4 – right hand – right leg; 5 – right hand – left leg; 6 – left hand – left leg; 7 – left hand – right leg; 8 – both hands – both legs; 9 – leg – leg; 10 – head – hands; 11 – head – legs; 12 – head – right hand; 13 – head – left hand; 14– head – right leg; 15 – head – left leg
The most dangerous current paths are those passing through the head and heart.
1. Electrical resistance of the human body.
2. The magnitude of the potential difference in the electrical circuit.
3. Duration of exposure.
4.The path of current through the human body.
5.Type and frequency of electric current.
6. Individual properties of a person.
7.Environmental conditions.
1. Electrical resistance of the human body.
The skin has the greatest resistance to electric current, so the resistance of the human body is determined mainly by the resistance of the skin. The electrical resistance of the human body with dry, clean and intact skin, measured at 20 V, ranges from 3-100 kOhm, and the resistance of the internal layers is 300-500 Ohm. The electrical resistance of the human body is a complex value, consisting of active and capacitive, but, as a rule, capacitive is neglected. The skin of the face, neck, and arms has the least resistance in the area above the palm, especially in areas facing the torso. With increasing exposure time, the resistance of the human body decreases, as this increases local heating of the skin, which leads to vasodilation and increased blood supply to this area, and accordingly an increase in sweating.
Sensible current– an electric current that causes noticeable irritation as it passes through the body. For alternating current it is 0.6-1.5 mA, for direct current 5-7 mA.
Non-releasing current- an electric current that causes irresistible convulsive contractions as it passes through the body. For alternating current it is 10-15 mA, for direct current 50-60 mA.
Fibrillation current is an electrical current that can cause asynchronous contractions of the heart muscle. The threshold current for alternating current is 100 mA, for direct current – 300 mA. With a duration of exposure of 1-2 seconds along the arm-arm or arm-leg path, the fibrillation current can reach 5 A. More than 5 A does not cause cardiac fibrillation - instantaneous cardiac arrest occurs.
5. Type and frequency of electric current.
Direct current is approximately 4-5 times safer than alternating current. The significantly lower risk of injury from direct current is confirmed by the practice of operating electrical installations. This provision is valid only for voltages of 250-300 V. But alternating current with a frequency of 50-1000 Hz poses a greater danger; with a further increase in frequency, the danger of injury decreases and completely disappears at a frequency of 45-50 kHz.
6. Individual properties of a person.
It has been established that physically healthy and strong people can more easily withstand electric shocks. People suffering from diseases of the cardiovascular system, skin, and internal secretion organs have increased susceptibility to electric current.
7. Environmental conditions.
Dampness, conductive dust, caustic vapors and gases have a destructive effect on the insulation of electrical equipment. The impact of current on humans is also aggravated by conductive floors and metal and grounded structures located close to electrical equipment.
Premises according to the danger of electric shock are divided into:
1) premises without increased danger;
2) premises with increased danger, which are characterized by the presence of one of the following conditions:
Dampness or conductive dust;
Conductive floors;
High room temperature (more than 35 C);
The possibility of simultaneous human contact with grounded metal structures on the one hand and metal housings of electrical equipment on the other.
3) especially dangerous premises – characterized by the presence of one of the conditions:
Particular dampness (relative humidity approximately 100%);
Presence of a chemically active or organic environment;
The presence of two or more high-risk conditions at the same time.
These are pronounced local (local) damage to body tissues caused by exposure to electric current or electric arc. Local damage most often affects the surface of human skin, but in some cases muscle tissue, as well as ligaments and bones, are also affected. Usually local electrical injuries are cured and the person’s performance is fully or partially restored. However, in some cases, local electrical injuries lead to human death. Local electrical injuries include:
electrical burns,
electrical signs (current marks),
electrometallization of skin,
· mechanical damage,
· electroophthalmia.
An electric shock is the effect of electric current on the human or animal body, as a result of which a convulsive contraction of the body muscles begins. Depending on the magnitude of the current and the time of exposure, the biological object can be conscious or unconscious, but with independent functioning of the respiratory organs and cardiovascular system. In the most severe conditions after electric shock, not only loss of consciousness is observed, but also problems in the functioning of the cardiovascular system, and even death.
23. Sequence and content of first aid measures. Methods of freeing the affected person from the effects of electric current, personal safety measures. Features of injury from atmospheric electricity (lightning) during lightning discharges, first aid.
First aid in case of electric shock is to immediately turn off the electrical installation or interrupt it by absolutely any in an accessible way circuits of the influence of electric current on a person, then, depending on the degree of damage, he will begin performing closed cardiac massage and organizing artificial respiration if the victim experiences cardiac arrest, as well as treating and applying a bandage to the affected parts of the body.
In case of electric shock, it is necessary to free the victim from its influence as soon as possible, since the severity of the electrical injury depends on the duration of this action.
If the victim holds the wire with his hands, his fingers are tightly squeezed and it is impossible to release the wire, then the first action of the person providing assistance is to turn off the electrical installation that the victim is touching. Disconnection is carried out using switches, a switch or other disconnecting device, as well as by removing or unscrewing the fuses (plugs), plug connection connector.
When the electrical installation is turned off, artificial lighting may go out at the same time, so you need to take care of this by turning on emergency lighting, etc.
In this case, it is necessary to take into account the explosion and fire hazards of the premises. When providing assistance to the victim, you must not touch him without taking precautions, as this is life-threatening; It is necessary to ensure that you do not come into contact with the live part and under the step voltage.
To separate the victim from live parts or wires with voltage up to 1,000 V, it is necessary to use a rope, stick, board or other dry object that does not conduct electric current.
If the clothes are dry and fall behind the body, then you can pull the victim away from live parts, avoiding contact (touching) with parts of the body, by the hem of a coat or jacket, jacket, or by the collar.
To isolate the hands, the person providing assistance must wear insulating gloves or wrap a scarf around the hand, put a cloth cap on the hand, or pull the sleeve of a jacket or coat over the hand. You can isolate yourself by using a rubber mat, a dry board or other improvised objects that do not conduct electricity (bedding, a bundle of clothes).
If an electric current passes into the ground through the victim, and he convulsively squeezes the wire in his hand, then you can separate the person from the ground by sliding a dry board under him or dragging him by his clothes. You can also cut the wire with an ax with a dry wooden handle or other tools with insulated handles (pliers, etc.).
After releasing the victim from the action of electric current, it is necessary to assess his condition.
If the victim has no consciousness, breathing, pulse, the skin is bluish, and the pupils are wide (0.5 cm in diameter), then he is in a state of clinical death and should immediately begin to revive the body using artificial respiration using the mouth-to-mouth method. or “mouth to nose” and external cardiac massage.
When you begin to revive the victim, you need to take care of calling medical help.
In the body of victims of atmospheric electricity, the same pathological changes are observed as in case of electric shock. The victim loses consciousness, falls, convulsions may occur, and breathing and heartbeat often stop. It is common to find “current marks” on the body, where electricity enters and exits. In case of death, the cause of cessation of basic vital functions is a sudden stop of breathing and heartbeat, from the direct effect of lightning on the respiratory and vasomotor centers of the medulla oblongata. A lightning strike victim requires hospitalization because he or she is at risk for electrical disturbances in the heart.
In case of lightning, the same assistance is provided as in case of electric shock.
The person struck by lightning is immediately given artificial respiration; if the heart stops, a closed massage is performed and the body is warmed up. Caffeine and analgin are given internally. If possible, antishock agents are administered subcutaneously: promedol, caffeine, ephedrine. After breathing has been restored, the victim should be given hot tea, the burns treated and transported to the hospital.
24. Flame burns, sequence and content of first aid measures. Frostbite, first aid measures (by stages).
Burn – tissue damage caused by exposure to high temperature, chemicals, electric current, ionizing radiation. Depending on the cause of occurrence, thermal, chemical, electrical, and radiation burns are distinguished. Sunburn is possible. The most common are thermal burns.
Thermal burns. During fires, the human body is affected by several damaging factors. The most dangerous of them is high temperature in the combustion zone, leading to heat stroke, burns of the skin and upper respiratory tract. Flame burns are much more severe than boiling liquid burns.. Among thermal burns of various localizations, the most dangerous are facial burns, they are accompanied by burns of the upper respiratory tract hot air.
The severity of the victim’s condition depends on the degree of the burn, its area and location. The degree of burn is determined by the depth of damage to the skin and underlying tissues. IV degree burns are classified.
First degree burn manifested by skin redness, swelling, pain.
Second degree burn characterized by the formation of blisters filled with a clear yellowish liquid, sharp redness of the skin, and burning pain.
Third degree burn accompanied by necrosis of all layers of the skin. The surface of the burn is covered with a scab - a dense gray-brown crust. Due to damage to the nerve endings, there is little or no pain. Dead tissue festers and is rejected. Healing is slow. A scar forms at the site of the burn.
IV degree burn characterized by charring of the skin, subcutaneous fat, muscles and even bones. Pain sensitivity is lost. Skin grafting is necessary to heal deep burns.
Determination of burn area
The burn area is determined using the “rule of nines.” The surface of the head and neck makes up 9% of the surface of the adult human body, one upper limb - 9%, one lower limb - 18% (thigh - 9%, lower leg and foot - 9%). The posterior surface of the human torso makes up 18% of the body surface, the anterior surface (chest, abdomen) – 18%, the perineum and external genitalia – 1%.
The area of the burn can also be determined using the “rule of the palm.” The area of the victim's palm is 1% of the surface of his body. The palm is projected over the affected area without touching the burned area of the body.
Burns of more than 15% of the body surface in adults are accompanied by burn shock. In children, burn shock develops when the burn area is 5–10% or more. There are 2 phases of burn shock: the first is the excitation phase, the second is the inhibition phase. The first phase is short-lived. The victims are excited and restless due to the continuous flow of pain impulses from the burn wounds. The second phase is characterized by pronounced inhibition of the activity of the nervous system, heart, lungs, kidneys and other organs. The indifferent look of the victims is noteworthy. Life danger arises even with second degree burns that occupy ⅓ of the body surface.
With extensive burns, toxic substances are formed in the affected areas. Penetrating into the blood, they spread throughout the body and cause intoxication. Microorganisms enter the burned areas of the skin, and the burn wounds begin to fester. Burn disease develops. The deeper the damage to the skin and underlying tissues and the larger the area of the burn, the more severe the victim’s condition and the worse the prognosis.
Frostbite is damage to body tissue caused by cold. Fingers, toes, nose, ears and face are more susceptible to frostbite. The severity of frostbite depends on the duration of the cold, as well as on the condition of the body.
When intoxicated, the body's thermoregulation is disrupted, and the likelihood of frostbite increases! Sign: sudden pallor of the skin and loss of sensitivity. The main goal of first aid is to stop exposure to cold and as much as possible fast recovery normal temperature chilled tissues. To do this you need:
immerse frostbitten areas of the body in water with a temperature of 37°C to 40°C, but not higher due to the risk of burns;
lightly rub frostbitten skin.
It is forbidden to rub frostbitten areas with snow or immerse them in cold water, as this will cause further hypothermia!
To prevent infection, sterile dressings are applied to frostbitten areas of the skin. If pain, tissue swelling, or blisters occur, you should seek medical help.
