Meteorological conditions, their influence on the microclimate. The influence of meteorological conditions on the body The influence of meteorological conditions on the body

Human labor activity always takes place under certain meteorological conditions, which are determined by a combination of air temperature, air speed and relative humidity, barometric pressure and thermal radiation from heated surfaces. If work takes place indoors, then these indicators together (with the exception of barometric pressure) are usually called microclimate of the production premises.

According to the definition given in GOST, the microclimate of industrial premises is the climate of the internal environment of these premises, which is determined by the combinations of temperature, humidity and air velocity acting on the human body, as well as the temperature of the surrounding surfaces.

If work is carried out in open areas, then meteorological conditions are determined by the climatic zone and season of the year. However, in this case, a certain microclimate is created in the working area.

All life processes in the human body are accompanied by the formation of heat, the amount of which varies from 4....6 kJ/min (at rest) to 33...42 kJ/min (during very hard work).

Microclimate parameters can vary within very wide limits, while a necessary condition for human life is to maintain a constant body temperature.

With favorable combinations of microclimate parameters, a person experiences a state of thermal comfort, which is an important condition for high labor productivity and disease prevention.

When meteorological parameters deviate from optimal ones in the human body, in order to maintain a constant body temperature, various processes begin to occur aimed at regulating heat production and heat transfer. This ability of the human body to maintain a constant body temperature, despite significant changes in the meteorological conditions of the external environment and its own heat production, is called thermoregulation.

At air temperatures ranging from 15 to 25°C, the body's heat production is at an approximately constant level (zone of indifference). As the air temperature decreases, heat production increases primarily due to

due to muscle activity (manifestation of which is, for example, trembling) and increased metabolism. As the air temperature rises, heat transfer processes intensify. The transfer of heat by the human body to the external environment occurs in three main ways (paths): convection, radiation and evaporation. The predominance of one or another heat transfer process depends on the ambient temperature and a number of other conditions. At a temperature of about 20°C, when a person does not experience any unpleasant sensations associated with the microclimate, heat transfer by convection is 25...30%, by radiation - 45%, by evaporation - 20...25%. When temperature, humidity, air speed, and the nature of the work performed change, these ratios change significantly. At an air temperature of 30°C, the heat transfer by evaporation becomes equal to the total heat transfer by radiation and convection. At air temperatures above 36°C, heat transfer occurs entirely due to evaporation.

When 1 g of water evaporates, the body loses about 2.5 kJ of heat. Evaporation occurs mainly from the surface of the skin and to a much lesser extent through the respiratory tract (10...20%). Under normal conditions, the body loses about 0.6 liters of fluid per day through sweat. During heavy physical work at an air temperature of more than 30 ° C, the amount of fluid lost by the body can reach 10...12 liters. During intense sweating, if the sweat does not have time to evaporate, it is released in the form of drops. At the same time, moisture on the skin not only does not contribute to the transfer of heat, but, on the contrary, prevents it. Such sweating only leads to the loss of water and salts, but does not perform the main function - increasing heat transfer.

A significant deviation of the microclimate of the working area from the optimal one can cause a number of physiological disorders in the body of workers, leading to a sharp decrease in performance even to occupational diseases.

Overheating. When the air temperature is more than 30°C and significant thermal radiation from heated surfaces, a violation of the body's thermoregulation occurs, which can lead to overheating of the body, especially if the loss of sweat per shift approaches 5 liters. There is increasing weakness, headache, tinnitus, distortion of color perception (everything turns red or green), nausea, vomiting, and body temperature rises. Breathing and pulse quicken, blood pressure first increases, then falls. In severe cases, heatstroke occurs, and when working outdoors, sunstroke occurs. A convulsive disease is possible, which is a consequence of a violation of the water-salt balance and is characterized by weakness, headache, and sharp cramps, mainly in the extremities. Currently, such severe forms of overheating practically never occur in industrial conditions. With prolonged exposure to thermal radiation, occupational cataracts can develop.

But even if such painful conditions do not occur, overheating of the body greatly affects the state of the nervous system and human performance. Research, for example, has established that by the end of a 5-hour stay in an area with an air temperature of about 31°C and a humidity of 80...90%; performance decreases by 62%. The muscle strength of the arms decreases significantly (by 30...50%), endurance to static force decreases, and the ability for fine coordination of movements deteriorates by about 2 times. Labor productivity decreases in proportion to the deterioration of meteorological conditions.

Cooling. Prolonged and strong exposure to low temperatures can cause various adverse changes in the human body. Local and general cooling of the body is the cause of many diseases: myositis, neuritis, radiculitis, etc., as well as colds. Any degree of cooling is characterized by a decrease in heart rate and the development of inhibition processes in the cerebral cortex, which leads to a decrease in performance. In particularly severe cases, exposure to low temperatures can lead to frostbite and even death.

Air humidity is determined by the content of water vapor in it. There are absolute, maximum and relative air humidity. Absolute humidity (A) is the mass of water vapor currently contained in a certain volume of air; maximum humidity (M) is the maximum possible content of water vapor in the air at a given temperature (saturation state). Relative humidity (B) is determined by the ratio of absolute humidity Ak maximum Mi expressed as a percentage:

Physiologically optimal is relative humidity in the range of 40...60%. High air humidity (more than 75...85%) in combination with low temperatures has a significant cooling effect, and in combination with high temperatures it contributes to overheating of the body. Relative humidity less than 25% is also unfavorable for humans, as it leads to drying of the mucous membranes and a decrease in the protective activity of the ciliated epithelium of the upper respiratory tract.

Air mobility. A person begins to feel the movement of air at a speed of approximately 0.1 m/s. Light air movement at normal temperatures promotes good health by blowing away the water vapor-saturated and superheated layer of air enveloping a person. At the same time, high air speed, especially at low temperatures, causes an increase in heat loss by convection and evaporation and leads to severe cooling of the body. Strong air movement is especially unfavorable when working outdoors in winter conditions.

A person feels the impact of microclimate parameters in a complex manner. This is the basis for the introduction of the so-called effective and effectively equivalent temperatures. Efficient temperature characterizes a person’s sensations under the simultaneous influence of temperature and air movement. Effectively equivalent Temperature also takes into account air humidity. A nomogram for finding the effective equivalent temperature and comfort zone was built experimentally (Fig. 7).

Thermal radiation is characteristic of any body whose temperature is above absolute zero.

The thermal effect of radiation on the human body depends on the wavelength and intensity of the radiation flux, the size of the irradiated area of ​​the body, the duration of irradiation, the angle of incidence of the rays, and the type of clothing of the person. The greatest penetrating power is possessed by red rays of the visible spectrum and short infrared rays with a wavelength of 0.78... 1.4 microns, which are poorly retained by the skin and penetrate deeply into biological tissues, causing an increase in their temperature, for example, prolonged irradiation of the eyes with such rays leads to clouding of the lens (occupational cataract). Infrared radiation also causes various biochemical and functional changes in the human body.

In industrial environments, thermal radiation occurs in the wavelength range from 100 nm to 500 microns. In hot shops, this is mainly infrared radiation with a wavelength of up to 10 microns. The intensity of irradiation of workers in hot shops varies widely: from a few tenths to 5.0...7.0 kW/m 2. When the irradiation intensity is more than 5.0 kW/m2

Rice. 7. Nomogram for determining effective temperature and comfort zone

within 2...5 minutes a person feels a very strong thermal effect. The intensity of thermal radiation at a distance of 1 m from the heat source on the hearth areas of blast furnaces and open-hearth furnaces with open dampers reaches 11.6 kW/m 2 .

The permissible level of thermal radiation intensity for humans in the workplace is 0.35 kW/m 2 (GOST 12.4.123 - 83 “SSBT. Means of protection against infrared radiation. Classification. General technical requirements”).

THEORETICAL PROVISIONS

Microclimate or meteorological conditions are a combination of temperature, humidity, air speed, and thermal radiation from surrounding objects.

The role of microclimate in human life is determined by the fact that the latter can proceed normally only if temperature homeostasis is maintained, which is achieved through the activity of various body systems (cardiovascular, respiratory, excretory, endocrine; energy, water-salt and protein metabolism). Tension in the functioning of various systems under the influence of an unfavorable microclimate (heating or cooling) can cause suppression of the body's defenses, the occurrence of pre-pathological conditions that aggravate the degree of influence of other industrial hazards (for example, vibration, chemicals and others), a decrease in working capacity and labor productivity, increasing morbidity rates.

A person encounters a heating microclimate when working in hot shops of various industries (metallurgical, glass, food, etc.), in deep mines, as well as when working outdoors in the summer (southern regions).

When working in a hot climate (air temperature in the shade 35-45 °C, soil 58-60 °C), the activity of the cardiovascular system weakens. A decrease in performance is observed already at an air temperature of 25-30 °C.

The performance of a person performing heavy physical work, even at an air temperature of 25°C and a humidity of 35±5%, decreases by 16,5%, and with air humidity 80 % - by 24%. Thermal irradiation 350 W/m2 (0,5 cal/cm 2 min) creates an additional load on various functional systems of the body, as a result of which (at a temperature

air 25 "C and humidity 35%) performance decreases by 27%. At air temperature 29.5±2.5°C and a humidity of 60%, by the end of the first hour of operation there is a decrease in performance.

A person encounters a cooling microclimate when working outdoors in winter and transitional periods (oil workers, construction workers, workers in the mining and coal industries, railway workers, geologists, etc.), as well as in industrial premises where there is low air temperature, for example in cold storage plants.

The human body has a unique ability to maintain

constant body temperature regardless of ambient temperature.

However, a person’s biological capabilities in maintaining a constant body temperature are very limited; they are based on heat exchange processes that constantly occur between the human body and the environment.

Heat exchange processes between humans and the environment are carried out in three ways: thermal radiation, convection and evaporation. Their share in the total heat exchange under normal conditions

amounts to 45%, 30-35%, 20-25% accordingly . Evaporation in humans occurs in two ways; most of the heat is removed through the mechanism of sweating and evaporation, and less is removed during respiration. The percentage of these heat exchange paths may change under the influence of meteorological conditions. Thus, with a decrease in ambient air temperature, the value of evaporation for heat exchange decreases and the share of convection increases. And with an increase in air temperature, the value of thermal radiation and

convection decreases and the value of evaporation increases, so that when the ambient temperature is equal to the temperature of the human body, heat exchange occurs exclusively due to evaporation.

As the body cools, heat transfer increases. Its reduction is achieved due to vasoconstriction in peripheral tissues. If this is not enough to ensure thermal equilibrium, then heat generation increases. But the human body’s ability to maintain thermal balance is limited, and the cooling effect of the external environment can lead to hypothermia. At the same time, the body’s overall resistance to the development of diseases decreases, vascular disorders and joint diseases occur. The process of lowering body temperature under the influence of microclimate is called hypothermia.

As the ambient temperature rises, heat transfer from the body decreases or even stops completely. This disrupts thermoregulation and leads to overheating. Severe overheating of the body is called heat stroke and is accompanied by increased heart rate, loss of coordination of movements, adynamia, depression of the central nervous system and even loss of consciousness. The process of increasing a person's body temperature is called hyperthermia. High temperatures have a negative impact on human health. Working in conditions of high temperature is accompanied by intense sweating, which leads to dehydration of the body, loss of mineral salts and water-soluble vitamins, causes serious and persistent changes in the activity of the cardiovascular system, increases the respiratory rate, and also affects the functioning of other organs and systems - weakened attention, coordination of movements worsens, reactions slow down, etc.

It should be borne in mind that the effect of climatic conditions is determined by a set of specific values ​​of temperature, humidity, and air speed.

Temperature in production premises is one of the leading factors determining the meteorological conditions of the production environment.

Humidity - water vapor content in the air. Affects human performance by changing the body’s thermal balance: low humidity (less 30 %) leads to loss of fluid and minerals through the skin and mucous membranes, and high (more 60 %) - to excessive sweating (to prevent overheating), but low sweat evaporation. Consequently, such conditions complicate a person’s muscular activity, create additional stress on the body’s adaptive systems, reduce performance and, therefore, require a reduction in the volume and intensity of physical activity. Types of air humidity: maximum, absolute, relative - Absolute air humidity - this is the amount of water vapor in a certain volume of air, mg/m3. Maximum air humidity- this is the maximum possible content of water vapor in a certain volume of air at a given temperature; if the moisture concentration in the air reaches a maximum and continues to grow, the processes of water condensation begin on the so-called. condensation nuclei, ions or fine dust particles and fog or dew falls. Relative humidity - This is the ratio of absolute air humidity to maximum air humidity, expressed as a percentage.

For human performance, not only temperature and humidity are of great importance, but also speed and direction of air movement, which affect both the temperature balance of the body and its psychological state (high-speed flows (more 6-7 m/s) irritate, weak ones - calm), on the frequency and depth of breathing, pulse rate, on the speed of a person’s movement. In conditions of high temperatures and normal humidity, increased air speeds cause an increase in evaporation from body surfaces, thereby improving heat transfer. In conditions of low temperatures, significant air speeds sharply worsen a person’s thermal state, greatly intensifying heat transfer.

Thermal radiation (infrared radiation) is invisible electromagnetic radiation with a wavelength of 0,76 to 540 nm, which has wave and quantum properties. The intensity of thermal radiation is measured in W/m2. Infrared rays passing through the air do not heat it, but when absorbed by solids, the radiant energy turns into thermal energy, causing them to heat up. The source of infrared radiation is any heated body.

The effect of thermal radiation on the body has a number of features, one of which is the ability of infrared rays of various lengths to penetrate to different depths and be absorbed by the corresponding tissues, producing a thermal effect, which leads to an increase in skin temperature, an increase in heart rate, changes in metabolism and blood pressure, and disease eye.

The microclimate parameters of industrial premises can be

very different, because they depend on the thermophysical features of the technological process, climate, season of the year, heating conditions and

ventilation. Therefore, the health status of workers who are

in production premises, their performance depends on the state of the microclimate in these premises .

The assessment of the thermal state of a person in industrial premises is carried out in accordance with the methodological recommendations of the Ministry of Health

No. 5168-90 "Assessment of a person’s thermal state in order to substantiate hygienic requirements for the microclimate of workplaces and preventive measures

cooling and overheating."

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ABSTRACT

on the topic:

« METEOROLOGICAL CONDITIONS, THEIR INFLUENCE

FOR MICROCLIMATEAIR ENVIRONMENT OF THE WORKPLACE

AND FOR THE ORGANIZATION OF VARIOUS TYPES OF WORK"

Microclimate of production premises - microclimatic conditions of the working environment (temperature, humidity, pressure, air speed, thermal radiation) of premises, which influence the thermal stability of the human body during labor.

Studies have shown that a person can live at an atmospheric pressure of 560-950 mmHg. Atmospheric pressure at sea level is 760 mm Hg. At this pressure a person feels comfortable. Both an increase and a decrease in atmospheric pressure have a negative effect on most people. As the pressure drops below 700 mm Hg, oxygen starvation occurs, which affects the functioning of the brain and central nervous system.

A distinction is made between absolute and relative humidity.

Absolute humidity - this is the amount of water vapor contained in 1 m3. air. Maximum humidity Fmax is the amount of water vapor (in kg) that completely saturates 1 m 3 of air at a given temperature (water vapor pressure).

Relative humidity is the ratio of absolute humidity to maximum humidity, expressed as a percentage:

c=A/Fmax*100% (2.2.1.)

When the air is completely saturated with water vapor, that is, A= Fmax (during fog), relative air humidity c = 100%.

The human body and its working conditions are also influenced by the average temperature of all surfaces enclosing the room; it has important hygienic significance.

Another important parameter is air speed . At elevated temperatures, air speed promotes cooling, and at low temperatures, hypothermia, so it must be limited, depending on the temperature environment.

Sanitary, hygienic, meteorological and microclimatic conditions not only affect the condition of the body, but also determine the organization of work, that is, the duration and frequency of employee rest and heating of the room.

Thus, the sanitary and hygienic parameters of the air in the working area can be physically dangerous and harmful production factors that have a significant impact on the technical and economic indicators of production.

According to DSN 3.3.6 042-99 “Sanitary standards for the microclimate of industrial premises”, according to the degree of influence on the thermal state of the human body, microclimatic conditions are divided into optimal and permissible. For the working area of ​​production premises, optimal and permissible microclimatic conditions are established, taking into account the severity of the work performed and the period of the year (Table 2.2.1., 2.2.2.).

Optimal microclimatic conditions - these are microclimate conditions that, with a long-term and systematic influence on a person, ensure the preservation of the thermal state of the body without the active work of thermoregulation. They maintain a sense of well-being, thermal comfort and the creation of a high level of labor productivity (Table 2.1.1.).

Acceptable microclimatic conditions, which, with a long-term and systematic influence on a person, can cause changes in the thermal state of the body, but are normalized and accompanied by intense work of thermoregulation mechanisms within the boundaries of physiological adaptation (Table 2.1.2.). In this case, there are no disturbances or deterioration in health, but there is discomfort in heat perception, deterioration in well-being and decreased performance.

Microclimate conditions beyond acceptable limits are called critical and lead, as a rule, to serious violations in the state of the organizationAthe baseness of man.

Optimal microclimate conditions are created for permanent jobs.

Table 2.2.1.

Optimal values ​​of temperature, relative humidity and air speed in the working area of ​​production premises.

Permanent workplace - a place where a worker spends more than 50% of his working time or more than 2 hours continuously. If, at the same time, work is performed at different points in the work zone, then the entire zone is considered a permanent workplace.

Non-permanent workplace - a place where a worker spends less than 50% of his working time or less than 2 hours continuously.

Distinguish between warm and cold periods of the year.

The warm period of the year is a period of the year that is characterized by an average daily external temperature above +10 0 C. The cold period of the year is a period of the year that is characterized by an average daily external temperature that is +10 0 C and below. Average daily outside air temperature is the average value of outside air measured at certain hours of the day at regular intervals. It is accepted according to the data of the meteorological service.

Light physical work (category I) covers activities in which energy consumption is 105-140 W (90-120 Kcal/hour) - category I-a and 141-175 W (121-150 Kcal/hour) - category I-b. Category I-b and category I-a include work that is performed while sitting, standing, or involving walking, and is accompanied by some physical stress.

Table 2.2.2

Permissible values ​​of temperature, relative humidity and sq.Oincrease in air movement in the working area of ​​production premises.

Moderate physical work (category II) covers activities in which energy expenditure is 176-132 W (151-200 Kcal/hour) - category II-a and 233-290 W (201-250 Kcal/hour) - category II-b. Category II-a includes work related to walking, moving small (up to 1 kg) products or objects in a standing or sitting position, and requiring a certain physical exertion. Category II-b includes work that is performed while standing, associated with walking, moving (up to 10 kg) loads and accompanied by moderate physical stress.

Heavy physical work (category III) covers activities in which energy expenditure is 291-349 W (251-300 Kcal/hour). Category III includes work associated with the constant movement of significant (over 10 kg) weights that require great physical effort.

For workers 1st andII- category of work during the thermal period rOyes (optimum temperature 25 0 C) 12.5% ​​of shift time is allocated for breaks: for rest - 8.5% and personal needs 4%. For workers along Sh-y kAcategories of work, time for rest and personal needs is determined by the formula:

To.l.n.=8.5+(Eph/292.89-1)x100 (2.2.2.)

where, T o.l.n. - time for rest and personal needs; 8.5 - rest time for workers of the IInd category of work; Ef - actual energy consumption of the worker according to physiological studies, J/s; 292.89 - maximum permissible energy consumption when performing work of category II, J/s.

Table 2.2.2 shows acceptable microclimate conditions.

Acceptable values ​​of microclimatic conditions are established in the case when it is not possible to ensure optimal microclimate conditions at the workplace in accordance with the technological requirements of production or economic feasibility.

The difference in air temperature along the height of the working area, while ensuring acceptable microclimate conditions, should not be more than 3 degrees for all categories of work, and horizontally should not go beyond the permissible temperatures of the categories of work.

Temperature, humidity, air flow speed, and infrared radiation in a room can significantly affect the human body. Human skin is a reliable protection against the negative influence of microclimatic conditions. It, like a protective screen, also protects a person from the penetration of pathogenic microorganisms. The weight of the skin is on average about 20% of the body weight. Under optimal environmental conditions, the skin releases up to 650 g of moisture and 10 g of CO 2 per day. In critical situations, in an hour the body can release from 1 to 3.5 liters of water and a significant amount of salts through the skin alone.

To ensure vital functions, the human central nervous system has mechanisms that, to a certain extent, reduce the influence of harmful and dangerous environmental factors. One of these factors is air temperature.

When the ambient temperature changes, body temperature remains constant due to the balance between thermal conductivity and heat transfer (for a healthy person, body temperature is 36.5 - 36.7 0 C).

As a result of redox processes during the absorption of food, heat is generated in the human body. Only 1/8 of the total heat generated is spent on muscle work; the rest is released into the environment to maintain the body’s thermal balance. Even under conditions of complete rest, the body of an adult produces about 7.5 * 10 6 J/day of thermal energy. During physical work, heat generation increases to 2.1*10 7 -..2.5*10 7 J/day.

The human body gives off or receives thermal energy through convection, radiation, conduction (conduction) and evaporation. In everyday life, human heat exchange most often occurs as a result of convection and radiation. However, conduction also occurs when a person directly contacts the surface of the body with objects (equipment, etc.). The above methods of transferring thermal energy provide heat exchange between the body and the environment. In this case, excess heat is released into the environment:

through the respiratory organs - about 5%, radiation - 40%, convection - 30%, evaporation - 20%, when heating food and water in the digestive tract - up to 5%.

Unfavorable conditions can cause overstrain of the thermoregulation mechanism, which leads to overheating or hypothermia of the body.

Convection, radiation, and heat production are also generally called sensible heat transfer. The ratios of heat transfer components and their quantitative characteristics have been studied quite well.

The above types of heat exchange can be described by the equation of thermal balance of the human body with the environment:

Where M- metabolic heat, W;

W- thermal equivalent of mechanical work, W;

Q With- heat transfer by evaporation, W;

Q To- convective heat transfer, W;

Q r- radiation heat transfer, W;

Q T- heat transfer due to thermal conductivity (conduction), W.

During the cold season, when t in

Heat loss by radiation is determined by the emissivity of the body surface and the temperature of surrounding fences and objects (walls, windows, furniture). The amount of this heat is about 42 - 52% of the total amount of heat given off.

Heat removal due to the evaporation of water depends on the amount of food taken and on the amount of muscular (physical) work performed.

Heat loss by evaporation can be divided into two components, resulting from invisible evaporation (non-sensitive perspiration) and sweating (sensitive perspiration).

At temperatures below the temperature of human skin, the amount of evaporated moisture remains almost constant. At higher temperatures, moisture loss increases. Sweating begins at an ambient temperature of 28 - 29 C, and at temperatures above 34 C, heat transfer due to evaporation and sweating is the only way of heat transfer from the body.

This type of heat transfer changes significantly with the presence of clothing. Even the adipose tissue underlying the skin, which is a poor conductor of heat, reduces this heat transfer.

The human body has the ability to maintain a constant body temperature using the thermoregulation mechanism. When we talk about constant temperature, we mean the temperature of the internal organs, since the surface temperature of different parts of the body varies significantly. Under normal conditions, the internal temperature of the body is maintained at 370.5 C. The mechanism for regulating the temperature of the human body is divided into chemical regulation processes associated with heat production and physical regulation processes associated with heat transfer. Both mechanisms are controlled by the nervous system.

Thermoregulation - This is the body’s ability to regulate heat exchange with the environment, maintaining body temperature at a constant level (36.6 +-0.5 0 C). Heat exchange is maintained by increasing or decreasing heat transfer to the environment (physical thermoregulation) or changes in the amount of heat produced in the body (chemical termOregulation).

Under comfortable conditions, the amount of heat generated per unit time is equal to the amount of heat released into the environment, i.e. balance comes - body heat balance.

Physical thermoregulation.

In conditions where the ambient temperature is significantly lower than 30 0 C and the humidity is less than 75%, all types of heat exchange operate: If the ambient temperature is higher than the temperature of the skin, then heat is absorbed by the body. In this case, heat transfer occurs only through the evaporation of moisture from the surface of the body and the upper respiratory tract, provided that the air is not yet saturated with water vapor. At high ambient temperatures, the heat transfer mechanism is associated with a decrease in thermal conductivity and increased sweating.

At an air temperature of 30 0 C and significant thermal radiation from heated surfaces of equipment, the body overheats, increasing weakness, headache, tinnitus, distortion of color perception are observed, and heat stroke is possible. Skin vessels dilate sharply, the skin turns pink due to increased blood flow. Subsequently, the reflex work of the sweat glands intensifies, and moisture is released from the body. When 1 liter of water evaporates, 2.3*10 6 J of thermal energy is released. At high ambient temperatures, a person experiences violent profuse sweating. In such conditions, he can lose up to 5 kg of his weight due to moisture per shift. Together with sweat, the body secretes a large amount of salts, mainly sodium chloride (up to 20-50g per day), as well as potassium, calcium, and vitamins. To prevent disruption of water-salt metabolism when performing heavy physical work in an area of ​​elevated temperature, it is necessary to carry out redehydration body, for example, workers should drink salted water (0.5% solution with vitamins).

At high temperatures there is a greater load on the cardiovascular system. When overheated, the secretion of gastric juice increases and then decreases, which is why diseases of the gastrointestinal tract are possible. Excessive sweating reduces the acid barrier of the skin, which causes pustular diseases. High ambient temperatures increase the degree of poisoning when working with chemicals.

Chemical thermoregulation .

Chemical thermoregulation occurs in cases where physical thermoregulation does not provide heat balance. Chemical thermoregulation consists of changing the rate of redox reactions in the body: the rate of combustion of nutrients and, accordingly, the energy released. At low ambient temperatures, heat generation increases, and at elevated temperatures, it decreases. Hypothermia can occur at low temperatures, especially in combination with high humidity and air mobility. An increase in humidity and air mobility reduces the thermal resistance of the air layer between the skin and clothing. Cooling the body (hypothermia) is the cause of myositis, neuritis, radiculitis, and colds. In particularly severe cases, exposure to low temperatures leads to frostbite and even death.

At low temperatures, thermoregulation is observed in vasoconstriction, increased metabolism, use of carbohydrate resources, etc. Depending on the effect of heat or cold, the lumen of peripheral vessels changes significantly. In this regard, blood circulation changes: for example, for the hand and forearm at low ambient temperatures it can decrease by 4 times, and at high temperatures it can increase by 5 times. When exposed to cold, blood circulation is redistributed, muscle activity is activated - trembling and “goose bumps” appear. Therefore, in winter in cold climate zones, the consumption of fats, carbohydrates, and proteins - the main energy sources in the body - increases. At low temperatures, high humidity is unfavorable. In damp weather at a temperature of 0-8 0 C, hypothermia and even frostbite are possible. A common phenomenon that occurs when working in low temperatures is vascular spasm, which is manifested by whitening of the skin, loss of sensitivity, and difficulty moving. First of all, the fingers and toes and the tips of the ears are susceptible to this process. In these places, swelling with a bluish tint, itching and burning appear. These phenomena do not disappear for a long time and occur again even with slight cooling. Hypothermia reduces the body's defenses and predisposes to respiratory diseases, primarily acute respiratory diseases, exacerbations of articular and muscular rheumatism, and the appearance of sacrolumbar radiculitis.

A significant amount of heat (excess heat) enters the room during operation of process equipment. Depending on the amount of heat generated, production facilities are divided into cold, characterized by a slight excess of sensible heat (no more than 90 KJ/h per 1 m 3 room) and hot , characterized by large excess heat (more than 90 KJ/h per 1 m 3 of room).

Has a significant role on human lifevla and air density . Humidity above 80% disrupts the processes of physical thermoregulation. Physiologically optimal relative humidity is 40-60%. Relative humidity less than 25% leads to drying of the mucous membranes and a decrease in the protective activity of the ciliated epithelium of the upper respiratory tract, which leads to weakening of the body and reduced performance.

A person begins to feel air movement at a speed of 0.1 m/s. Light air movement at normal temperatures promotes good health. High air speed leads to strong cooling of the body. High air humidity and weak air movement significantly reduce the evaporation of moisture from the skin surface. In this regard, sanitary standards for the microclimate of industrial premises have established optimal and permissible parameters for the microclimate of industrial premises. Meteorological and microclimatic conditions play a vital role in work and rest. Of particular importance is the assessment and accounting of sanitary and hygienic conditions for workers performing most of their functional duties, such as eliminating the consequences of accidents, natural disasters, providing assistance to the population, cordoning off hazardous areas, etc., at workplaces located outside buildings and structures. At an air temperature of 25-33 0 C, a special mode of work and rest is provided with mandatory air conditioning. At a temperature of 33 0 C, work outdoors must be stopped.

During the cold period of the year (outside air temperature below 10 0 C), the work and rest regime depends on the temperature and air speed, and in northern latitudes - on the severity of the weather. The degree of hardness is characterized by temperature and air speed. An increase in air speed by 1 m/s corresponds to a decrease in air temperature by 2 0 C.

At the first degree of weather severity (-25 0 C), 10-minute breaks for rest and heating are provided after every hour of work. At the second degree (from -25 to -30 0 C), 10-minute breaks are provided every 60 minutes from the start of work and after lunch and every subsequent 50 minutes of work. At the third degree of hardness (from -35 to -45 0 C), breaks of 15 minutes are provided after 60 minutes. from the beginning of the shift and after lunch and every 45 minutes of work. When the ambient temperature is below -45 0 C, work in the open air is carried out in exceptional cases with the establishment of certain work and rest schedules.

Meteorological conditions determine whether most construction work can be carried out or stopped. Work must be stopped during heavy snowfall, fog, and poor lighting. For example, installation work and crane operations must be stopped at a wind force of 10 m/s, and at a speed of 15 m/s the crane must be secured with anti-theft devices. Meteorological conditions can affect labor productivity; their negative impact can lead to the accumulation of fatigue and weakening of the body and, as a result, to accidents and the development of occupational diseases.

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Description of the optimal and permissible microclimatic conditions in which a person can work. Study of the calculated parameters of internal air. Purpose of ventilation, air conditioning and heating systems. Acceptable air humidity parameters.

The meteorological conditions of industrial premises (microclimate) have a great influence on a person’s well-being and on his labor productivity.

To perform various types of work, a person needs energy, which is released in his body in the processes of redox breakdown of carbohydrates, proteins, fats and other organic compounds contained in food.

The released energy is partially spent on performing useful work, and partially (up to 60%) is dissipated as heat in living tissues, heating the human body.

At the same time, thanks to the thermoregulation mechanism, body temperature is maintained at 36.6 °C. Thermoregulation is carried out in three ways: 1) changing the rate of oxidative reactions; 2) changes in the intensity of blood circulation; 3) changes in the intensity of sweating. The first method regulates heat release, the second and third methods regulate heat removal. The permissible deviations of the human body temperature from normal are very insignificant. The maximum temperature of internal organs that a person can withstand is 43 °C, the minimum is plus 25 °C.

To ensure the normal functioning of the body, it is necessary that all generated heat is removed to the environment, and changes in microclimate parameters are within the zone of comfortable working conditions. If comfortable working conditions are violated, increased fatigue is observed, labor productivity decreases, overheating or hypothermia of the body is possible, and in especially severe cases, loss of consciousness and even death occurs.

The removal of heat from the human body to the environment Q is carried out by convection Q conv as a result of heating the air washing the human body, infrared radiation to surrounding surfaces with a lower temperature Q iz, evaporation of moisture from the surface of the skin (sweat) and the upper respiratory tract Q ex. Comfortable conditions are ensured by maintaining the thermal balance:

Q =Q conv + Q iiz +Q use

Under normal conditions temperature and low air speed in the room, a person at rest loses heat: as a result of convection - about 30%, radiation - 45%, evaporation -25%. This ratio may change, since the process of heat transfer depends on many factors. The intensity of convective heat transfer is determined by the ambient temperature, mobility and moisture content of the air. Radiation of heat from the human body to surrounding surfaces can only occur if the temperature of these surfaces is lower than the temperature of the surface of clothing and open parts of the body. At high temperatures of surrounding surfaces, the process of heat transfer by radiation occurs in the opposite direction - from the heated surfaces to the person. The amount of heat removed during the evaporation of sweat depends on temperature, humidity and air speed, as well as on the intensity of physical activity.

A person has the greatest working capacity if the air temperature is between 16-25 ° C. Thanks to the mechanism of thermoregulation, the human body responds to changes in ambient temperature by narrowing or dilating blood vessels located near the surface of the body. As the temperature decreases, the blood vessels narrow, the flow of blood to the surface decreases and, accordingly, the removal of heat by convection and radiation decreases. The opposite picture is observed when the ambient temperature rises: blood vessels dilate, blood flow increases and, accordingly, heat transfer to the environment increases. However, at a temperature of the order of 30 - 33 ° C, close to the human body temperature, heat removal by convection and radiation practically stops, and most of the heat is removed by evaporation of sweat from the surface of the skin. Under these conditions, the body loses a lot of moisture, and with it salt (up to 30-40 g per day). This is potentially very dangerous and therefore measures must be taken to compensate for these losses.

For example, in hot shops, workers receive salted (up to 0.5%) carbonated water.

Humidity and air speed have a great influence on human well-being and the associated thermoregulation processes.

Relative air humidity φ is expressed as a percentage and represents the ratio of the actual content (g/m 3) of water vapor in the air (D) to the maximum possible moisture content at a given temperature (Do):

or absolute humidity ratio P n(partial pressure of water vapor in air, Pa) to the maximum possible P max under given conditions (saturated vapor pressure)

(Partial pressure is the pressure a component of an ideal gas mixture would exert if it occupied one volume of the entire mixture).

Heat removal during sweating directly depends on air humidity, since heat is removed only if the released sweat evaporates from the surface of the body. At high humidity (φ > 85%), the evaporation of sweat decreases until it completely stops at φ = 100%, when sweat flows in drops from the surface of the body. Such a violation of heat removal can lead to overheating of the body.

Low air humidity (φ< 20 %), наоборот, сопровождается не только быстрым испарением пота, но и усиленным испарением влаги со слизистых оболочек дыхательных путей. При этом наблюдается их пересыхание, растрескивание и даже загрязнение болезнетворными микроорганизмами. Сам же процесс дыхания может сопровождаться болевыми ощущениями. Нормальная величина относительной влажности 30-60 %.

Air speed indoors significantly affects a person’s well-being. In warm rooms at low air speeds, heat removal by convection (as a result of heat washing by air flow) is very difficult and overheating of the human body can be observed. An increase in air speed helps to increase heat transfer, and this has a beneficial effect on the condition of the body. However, at high air speeds, drafts are created, which lead to colds at both high and low indoor temperatures.

The air speed in the room is set depending on the time of year and some other factors. So, for example, for rooms without significant heat releases, the air speed in winter is set within 0.3-0.5 m/s, and in summer - 0.5-1 m/s.

In hot shops (rooms with an air temperature of more than 30 ° C), the so-called air shower. In this case, a stream of humidified air is directed at the worker, the speed of which can reach up to 3.5 m/s.

Has a significant impact on human life atmospheric pressure . Under natural conditions at the Earth's surface, atmospheric pressure can fluctuate between 680-810 mm Hg. Art., but practically the life activity of the absolute majority of the population takes place in a narrower pressure range: from 720 to 770 mm Hg. Art. Atmospheric pressure decreases rapidly with increasing altitude: at an altitude of 5 km it is 405, and at an altitude of 10 km - 168 mm Hg. Art. For a person, a decrease in pressure is potentially dangerous, and the danger comes from both the decrease in pressure itself and the rate of its change (painful sensations occur with a sharp decrease in pressure).

With a decrease in pressure, the supply of oxygen to the human body during breathing deteriorates, but up to an altitude of 4 km, a person, due to an increase in the load on the lungs and cardiovascular system, maintains satisfactory health and performance. Starting from an altitude of 4 km, the supply of oxygen decreases so much that oxygen starvation may occur. - hypoxia. Therefore, when at high altitudes, oxygen devices are used, and in aviation and astronautics - spacesuits. In addition, aircraft cabins are sealed. In some cases, such as diving or tunneling in water-saturated soils, workers are exposed to high pressure conditions. Since the solubility of gases in liquids increases with increasing pressure, the blood and lymph of workers are saturated with nitrogen. This creates a potential danger of so-called “ decompression sickness" which develops when there is a rapid decrease in pressure. In this case, nitrogen is released at high speed and the blood seems to “boil.” The resulting nitrogen bubbles clog small and medium-sized blood vessels, and this process is accompanied by sharp pain (“gas embolism”). Disturbances in the functioning of the body can be so serious that they sometimes lead to death. To avoid dangerous consequences, the pressure reduction is carried out slowly, over many days, so that excess nitrogen is removed naturally when breathing through the lungs.

To create normal weather conditions in production premises, the following measures are taken:

mechanization and automation of heavy and labor-intensive work, which frees workers from performing heavy physical activity, accompanied by a significant release of heat in the human body;

remote control of heat-emitting processes and devices, which makes it possible to eliminate the presence of workers in the zone of intense thermal radiation;

removal of equipment with significant heat generation to open areas; when installing such equipment in closed premises, it is necessary, if possible, to exclude the direction of radiant energy to workplaces;

thermal insulation of hot surfaces; thermal insulation is calculated in such a way that the temperature of the external surface of the heat-emitting equipment does not exceed 45 ° C;

installation of heat-protective screens (heat-reflecting, heat-absorbing and heat-removing);

installation of air curtains or air showering;

installation of various ventilation and air conditioning systems;

arrangement of special places for short-term rest in rooms with unfavorable temperature conditions; in cold shops these are heated rooms, in hot shops these are rooms into which cooled air is supplied.

In the process of activity, a person is influenced by certain meteorological conditions or microclimate. The main microclimate indicators include temperature, relative humidity, and air speed. The intensity of thermal radiation from various heated surfaces has a significant impact on microclimate parameters and the state of the human body.

Relative humidity is the ratio of the actual amount of water vapor in the air at a given temperature to the amount of water vapor saturating the air at that temperature.

If there are various heat sources in the room, the temperature of which exceeds the temperature of the human body, then the heat from them spontaneously transfers to a less heated body, i.e. to a person. There are three methods of heat propagation: thermal conductivity, convection, and thermal radiation.

Thermal conductivity is the transfer of heat due to the random thermal movement of microparticles (atoms, molecules, electrons).

Convection is the transfer of heat due to the movement and mixing of macroscopic volumes of gas or liquid.

Thermal radiation is the process of propagation of electromagnetic oscillations with different wavelengths, caused by the thermal movement of atoms or molecules of the emitting body. In real conditions, heat is transferred in a combined way. A person is constantly in a state of thermal interaction with the environment. For the normal course of physiological processes in the human body, maintaining an almost constant body temperature is required. The body's ability to maintain a constant temperature is called thermoregulation (removal of generated heat into the surrounding space).

The effect of ambient temperature on the human body is primarily with the narrowing and expansion of blood vessels in the skin. Due to the effect of low temperatures, blood vessels narrow, as a result of which the flow of blood to the surface of the body slows down and heat transfer from the surface of the body due to convection and radiation decreases. At high temperatures the opposite picture is observed.

High humidity complicates heat exchange between the human body and the external environment due to reduced evaporation of moisture from the surface of the skin, and low humidity leads to drying out of the mucous membranes of the respiratory tract. Air movement improves heat exchange between the body and the external environment.

Constant deviation from normal microclimate parameters leads to overheating or hypothermia of the human body and associated negative consequences: profuse sweating, increased heart rate and breathing, dizziness, convulsions, heat stroke.

Regulatory documents introduce the concepts of optimal and permissible microclimate parameters.

Radiation: first aid

Radiation is an integral part of the environment. It enters the environment from natural sources created by man (nuclear power plants, nuclear weapons testing). Natural sources of radiation include: cosmic rays, radioactive rocks, radioactive chemicals and elements found in food and water. Scientists call all types of natural radiation the term “background radiation.”

Other forms of radiation enter nature as a result of human activity. People receive varying doses of radiation during medical and dental x-rays.

Radioactivity and accompanying radiation existed in the Universe constantly. Radioactive materials are part of the Earth, and even humans are slightly radioactive, because... Radioactive substances are present in the smallest quantities in any living tissue. The most unpleasant property of radioactive radiation is its effect on the tissues of a living organism, so measuring instruments are needed that would provide operational information.

The peculiarity of ionizing radiation is that a person will begin to feel its effects only after some time has passed. Different types of radiation are accompanied by the release of different amounts of energy and have different penetrating abilities, so they have different effects on the tissues of a living organism.

Alpha radiation is blocked, for example, by a sheet of paper and is practically unable to penetrate the outer layer of the skin. Therefore, it does not pose a danger until radioactive substances emitting alpha particles enter the body through an open wound, in food, water or air, then they become extremely dangerous.

A beta particle has greater penetrating ability: it penetrates into body tissue to a depth of 1-2 cm or more, depending on the amount of energy. The penetrating power of gamma radiation is very high, spreading at the speed of light: it can only be stopped by a thick lead or concrete slab.

You can take protective measures, but it is almost impossible to completely free yourself from the effects of radiation. The level of radiation on Earth varies.

If sources of ionizing radiation come in through breathing, drinking water or food, then such radiation is called internal.

Of all the natural sources of radiation, the greatest danger is radon - a heavy gas that is tasteless, odorless and, at the same time, invisible: with its daughter products. Radon is released from the earth's crust everywhere, but a person receives the main radiation from radon while in a closed, unventilated room. Radon concentrates indoors only when they are sufficiently isolated from the external environment. Sealing rooms for the purpose of insulation only makes matters worse, since this makes it even more difficult for radioactive gas to escape from the room.

The most common building materials - wood, brick and concrete - emit relatively little radon. Granite, pumice, and products made from alumina raw materials are much more radioactive. Another source of radon entering residential areas is water and natural gas. Water from deep wells or artesian wells contains a lot of radon. When boiling or cooking hot foods, radon disappears almost completely. A great danger is the ingress of water vapor with a high content of radon into the lungs along with inhaled air in the bathroom or steam room.

Other sources of radiation, unfortunately, are created by man himself. The sources of artificial radiation are artificial radionucleides, bundles of neurons and charged particles created with the help of nuclear reactors and accelerators. They are called man-made sources of ionizing radiation.

Emergency situations, such as the Chernobyl accident, can have an uncontrollable impact on people

High doses of radiation pose a deadly threat to humans. The resulting dose of 500 rem or more will kill almost anyone within a few weeks. A dose of 100 rem can cause severe radiation sickness. Radiation contributes to an increase in cancer and causes various fetal defects.

Scientists say that on average a person annually receives a total dose of radiation equal to 150-200 millirem. Most radiation (about 80 millirem) comes from natural radiation sources or from medical examinations (about 90 millirem). The radiation received as a result of scientific research is 1 millirem, from the operation of nuclear installations - 4-5, from the use of household appliances - 4-5 millirem. The dose of radiation in air is measured in roentgens, and the dose absorbed by living tissue is measured in rads. To assess the intensity of contamination of an area, the concept of “radiation dose rate” was introduced; it is measured in roentgens (R), milliroentgens (mR), microroentgens (μR) per hour. From the moment the territory is contaminated, with every sevenfold increase in time, the radiation level decreases by 10 times. If after an hour the radiation level in the area was 100 R/h, then after 7 hours it will be 10 R/h, and after 49 hours – 1 R/h.