What about the parameters of the microclimate. Microclimate in the workplace: how to keep the situation under control
Hygienic requirements for the microclimate of industrial premises make it possible to maintain a healthy, favorable environment for the human body at the workplace. They are contained in a regulatory document approved by the Decree of the Goskomsanepidnadzor of Russia dated October 1, 1996 No. 21. This document is mandatory for all organizations, institutions, enterprises, regardless of their form of ownership and legal form. Let's take a look at its main points.
Microclimate indicators
Before judging the microclimate of a production facility and making any decisions to correct it, it is necessary to “measure” its real state in a certain way and according to certain parameters.
In accordance with paragraph 4.3 of the Sanitary Rules, the microclimate of the production premises is measured using predetermined indicators. These include indicators such as:
- air temperature;
- surface temperature;
- relative humidity;
- air speed;
- intensity of thermal radiation.
It should be noted that these figures may vary depending on certain conditions. Namely, on what period of the year the work is performed on the measured area (cold or warm) and how intensive this work is.
For example, if work is performed during the cold season and is not associated with a large energy expenditure human body(for example, the work of an operator at a computer), the parameters of the microclimate in the room should be as follows: air temperature not less than + 22-24 ° С (surface temperature not less than + 21-25 ° С, relative humidity 60-40%, air speed 0.1 m/s). And if the work is performed in the warm season and during its execution the body spends too much energy (for example, the worker unloads the “heavy” production equipment), the temperature norm in the room should fluctuate within + 18-20 ° С (surface temperature is not higher than +17 -21 °С, relative air humidity 60-40%, and air velocity 0.3 m/s).
HR Dictionary
Room microclimate- this is the state of the internal environment of the room, which has a direct impact on the human body.
Production room- a closed space in a specially designed building (structure), in which people work constantly (in shifts) or periodically (during the working day).
Workplace- the section of the premises on which during work shift or part of it is carried out labor activity. A workplace can be several sections of a production facility. If these areas are located throughout the premises, then the entire area of \u200b\u200bthe premises is considered the workplace.
Harmful production factor- an environmental factor, the impact of which can cause an occupational disease in an employee, a temporary or permanent decrease in working capacity, increase the frequency of somatic and infectious diseases, lead to disruption of the reproductive function of the body.
Optimal and Permissible Conditions
Sanitary standards, which we are talking about today, give a clear gradation of the microclimate conditions of industrial premises. In accordance with this document, environmental conditions are divided into optimal and permissible.
Optimal microclimatic conditions differ in that they provide complete comfort to the thermal and functional state of the human body during an eight-hour work shift. This happens with a minimum tension of the mechanisms of thermoregulation, does not cause deviations in the state of health. Optimal conditions microclimates create the prerequisites for a high level of performance and are preferred in the workplace.
AT without fail these conditions are established at the workplaces of production premises where operator-type work is performed. This is directly stated in paragraph 5.2 of the Sanitary Rules. Usually these works are associated with neuro-emotional stress of a person (work in cabins, on consoles and control posts for technological processes, in computer rooms, etc.). The list of other jobs and types of work, in which optimal microclimate values should be ensured, are determined by the Sanitary Rules for individual industries and other documents agreed with the State Sanitary and Epidemiological Supervision authorities.
HR Dictionary
Cold period of the year- this is the period of the year, characterized by an average daily outdoor temperature of + 10 ° C and below.
Average daily outdoor temperature- the average value of the outdoor air temperature, measured at certain hours of the day at regular intervals. It is taken according to the meteorological service.
Warm period of the year- this is the period of the year, characterized by an average daily outdoor temperature above + 10 ° C.
Permissible microclimatic conditions established according to the criteria of the permissible and functional state of a person for the period of an eight-hour work shift. They are not as comfortable as optimal, however do not cause damage or any other impairment of human health. However, in some cases, such conditions can lead to general or local sensations of thermal discomfort, tension in the mechanisms of thermoregulation, deterioration in well-being and a decrease in human performance. Permissible values of microclimate indicators are established in cases where, according to technological requirements, technical and economic reasons optimal values cannot be provided. In separate rooms of the depot for the repair of rolling stock of railway transport (for example, where wagons are dried), the air temperature and its humidity cannot be set at the level of optimal values. Otherwise, both the technological process itself and the quality of the manufactured products will suffer.
When the microclimate becomes harmful
In practice, it often happens that in industrial premises (again, due to technological requirements for the production process), it is impossible to establish not only optimal, but also permissible standard values for microclimate indicators. In this case, the microclimate conditions should be considered as harmful and dangerous. An example is the work carried out, for example, in paint and varnish or steel-smelting shops of various manufacturing enterprises. In this case, to prevent the adverse effects of the microclimate on the body of the employee, the employer must take certain measures.
In the room of a mini-bakery, equipped with two bakery products, the microclimate indicators (for technological reasons) are set higher allowable rate. So, in the warm period of the year, the actual air temperature in the room reaches +29 °С (instead of the permissible +20-21.9 °С), and the surface temperature +35 °С (instead of the permissible +24.1-28.0 °С ). To compensate for the impact of harmful factors, the administration of the bakery equipped the utility rooms with showers, and also established an additional rest break for employees, which is included in the total duration working hours(Article 224 of the Labor Code of the Russian Federation).
Who controls the microclimate in the workplace
And now let's talk about who should directly control the state of the microclimate in the production room. We must make a reservation right away that such a complex and painstaking task is only possible for specialists directly in this field. This refers to specialists in instrumental measurement of environmental hazard factors. Ordinary employees simply cannot cope with such a task. However, personnel officers are often entrusted with overseeing labor protection issues in an organization, so it is necessary to know how to act in a particular case and where to turn for help.
By general rule the problem of measuring the microclimate at the workplace should be dealt with by employees laboratories the organization itself. However, not every company has the financial and technical means to maintain such a specialized unit. In this case, if this is not possible, the company may involve third-party organizations.
The question arises: can all environmental companies provide such services? We answer: no, not all. By law, only:
- centers of state sanitary and epidemiological surveillance;
- laboratories of the bodies of the State Expertise of Working Conditions of the Russian Federation;
- laboratories accredited (certified) for the right to carry out the indicated measurements.
Specialists of the listed organizations and departments will promptly conduct all the necessary research. If the microclimate indicators deviate from the normative ones, they will give clear instructions on how to correct them.
If you want to involve a third-party organization to study the microclimate of a production facility, then before concluding an appropriate contract with it, demand from its management documents confirming the right to work in this area. This is a document for the right to measure production factors and certificate, confirming the accreditation of the structural unit as a testing laboratory for SSOT.
Lab #4
WORKPLACE MICROCLIMATE STUDY
Objective: get an idea about the main parameters of the microclimate; to study the principles of rationing the microclimate in the premises; research and evaluate the parameters of the microclimate in the workplace.
Theoretical part
1. Microclimate and its impact on the human body
Microclimate- this is a set of environmental parameters that affect the thermal sensations of a person: temperature, humidity and air velocity and the intensity of thermal radiation from surrounding surfaces, characteristic of a particular room.
The microclimate has a significant impact on the performance of a person, his well-being and health.
The need to take into account the parameters of the microclimate is predetermined by the conditions of the heat balance between the human body and the environment of the premises.
Man is constantly in the process of thermal interaction with the environment. The amount of heat generated by the human body Q depends on the degree of physical stress and microclimate parameters. In order for the physiological processes in his body to proceed normally, the heat released by the body must be completely removed to surrounding a person Wednesday. Normal thermal sensations correspond to the equality between the amounts of heat released by the human body and given to the environment.
Heat exchange between the human body and the environment is carried out using the following processes:
heat transfer (thermal conduction) through clothing Q T;
convection Q K;
thermal radiation to the environment Q izl;
Evaporation of moisture (sweat) from the surface of the skin Q COI;
breathing (heating the inhaled air) Q D.
Heat transfer(thermal conductivity) consists in the transfer of heat from one particle to another in direct contact.
Convection is a process of heat exchange between the human body and the environment, carried out by moving air. Convective heat transfer depends on the ambient temperature, air velocity, air humidity and barometric pressure.
thermal radiation is a heat exchange process carried out by emitting infrared electromagnetic waves. Thermal rays directly do not heat the air, but are well absorbed by solids and, therefore, heat them. heating up solid bodies they themselves become sources of heat and already by convection heat the air.
At an ambient temperature equal to or higher than the surface temperature of the human body, heat transfer occurs only in the form of sweat, the evaporation of 1 g of which takes about 0.6 kcal. At rest at an ambient temperature of 18 ° C, the proportion Q K accounts for about 30% of all heat dissipation, Q izl» 45%, Q COI» 20% and Q D" 5 %.
When the air temperature, its speed of movement and humidity change, when there are heated surfaces near a person, in conditions of physical work, etc. these ratios change significantly. So, at high air temperature (30 °C and above), especially when performing hard physical work, sweating can increase tenfold and reach 1-1.5 l/h.
Normal thermal well-being of a person (comfortable conditions corresponding to this type of activity) is ensured if the condition of thermal balance is met:
Q H \u003d Q T + Q K + Q ISL + Q ISP + Q D,
where Q H- the amount of heat generated by the human body.
Temperature internal organs a person is maintained constant at a level of about 36.6 ° C. This ability of the human body to maintain a constant temperature when the parameters of the microclimate change and when performing work of varying severity is called thermoregulation. If the thermal equilibrium is disturbed (for example, heat transfer is less than heat release), then heat accumulates in the body - overheating. If heat transfer is greater than heat release, then hypothermia of the body occurs.
Comfortable meteorological conditions are an important factor ensuring high labor productivity and disease prevention. If the hygienic norms of the microclimate are not observed, the working capacity of a person decreases, the risk of injuries and a number of diseases, including occupational ones, increases.
The main parameters of the microclimate
Air humidity . Humidity characterizes the degree of its saturation with water vapor. The same air temperature, depending on the degree of its humidity, is felt by a person in different ways. Distinguish between absolute and relative humidity.
Absolute humidity(R ABS) is the amount of water vapor contained in 1 m 3 of air, i.e. vapor density (g / m 3). Absolute humidity is also characterized by water vapor pressure (hPa), i.e., the partial pressure that water vapor would exert on the walls of a vessel if all other air components were removed from this vessel.
Air with a limiting water vapor content at a given temperature is characterized by saturated vapor pressure ( R US), which increases with increasing air temperature. After reaching R US water vapor starts to condense.
Absolute humidity in itself does not indicate whether water vapor is in a saturated or unsaturated state, therefore the concept relative humidity.
Relative Humidity (φ ) is determined by the expression:
φ = (P ABS /P US)·100, %. (one)
Relative humidity affects human heat transfer, for example, the rate of evaporation of moisture from the surface of the skin.
Air temperature has a great impact on the state of the human body. Heat ambient air increases fatigue, can lead to overheating of the body or cause heat stroke. With a slight overheating, there is a slight increase in human body temperature, profuse sweating, a feeling of thirst appears, breathing and pulse become more frequent. In more severe conditions, heat stroke can occur, accompanied by an increase in temperature to 40 - 41 ° C, a weak and rapid pulse, and loss of consciousness. A characteristic sign of the onset of heat stroke is the almost complete cessation of sweating. Heat stroke can be fatal. Low ambient temperature can cause local or general hypothermia of the human body, cause colds or frostbite.
Air speed It has great importance to create favorable living conditions. At a high air velocity, the intensity of convective heat transfer increases. If the air currents have a temperature below the temperature of the skin surface (30 - 33 ° C), they have a refreshing effect on the human body, and at temperatures above 37 ° C they act depressingly. The human body begins to feel air currents at a speed of about 0.15 m/s.
thermal radiation from heated surfaces plays an important role in creating unfavorable microclimatic conditions. The action of radiant heat is not limited to the changes that occur on the irradiated area of the skin - the entire body reacts to irradiation. In the body there are biochemical changes, disorders in the cardiovascular and nervous systems. With prolonged exposure to infrared rays, cataracts of the eyes (clouding of the lens) may occur.
Thermal sensations of a person depend on a combination of microclimatic parameters and on the intensity of physical work.
To assess the complex effect of microclimate parameters on the human body at low energy costs, the method of equivalent effective temperatures is used. This method makes it possible, on the basis of data on microclimate parameters, to judge the thermal state of a person. For its use, the concept equivalent effective temperature (EET), which characterizes the thermal sensation of a person under the simultaneous influence of temperature, humidity and air velocity. EET is measured by a still air temperature of 100% relative humidity, at which a person's thermal sensation is the same as for a given combination of temperature, humidity and air velocity.
The EET region in the temperature range from 17 to 22 °C corresponds to comfort zone, within which it is possible to distinguish the line of comfort corresponding to EET = 19 °C, at which almost all the studied people experience a feeling of comfort.
The figure shows a nomogram that allows you to determine the influence of microclimate parameters on a person's thermal sensation.
3. Rationing of microclimate parameters
The normalized parameters of the microclimate in industrial premises are: air temperature; relative humidity; air speed; the temperature of the room surfaces (walls, ceiling, floor) and technological equipment; intensity of thermal radiation. When normalizing microclimate parameters, the intensity of energy consumption of workers (the category of work according to severity), the period of the year, and the time spent at the workplace are taken into account.
At the same time, optimal and permissible microclimatic conditions are distinguished.
Optimal microclimatic conditions represent such combinations of microclimate parameters that provide a feeling of thermal comfort during an 8-hour work shift with minimal stress on thermoregulation mechanisms
Permissible microclimatic conditions can lead to a feeling of thermal discomfort, tension in the mechanisms of thermoregulation, deterioration in well-being and performance. Under the condition of an 8-hour work shift, they do not cause damage or health problems. Permissible values of microclimate parameters are set in cases where, due to technological requirements, technical and economically justified reasons, optimal values \u200b\u200bcannot be provided.
Nomogram of Equivalent Effective Temperatures
Depending on the energy consumption per unit of time, work is divided into the following categories.
¨ light physical work (category I) - activities with intensity of energy consumption up to 174 W.
Category Ib include work performed while sitting, standing or walking and accompanied by some physical stress with an energy consumption intensity of 140 - 174 watts.
¨ Physical work of moderate severity (category II) - activities with an intensity of energy consumption of 175 - 290 W.
Category IIa include work associated with constant walking, moving small (up to 1 kg) products or objects in a standing or sitting position and requiring a certain physical exertion with an energy intensity of 175 - 232 W.
Category IIb includes work related to walking, moving and carrying loads up to 10 kg and accompanied by moderate physical stress with an energy consumption intensity of 233 - 290 W.
¨ Heavy physical work (category III) - types of activities with an intensity of energy consumption with an energy consumption of more than 290 W. These works are associated with constant movement, moving and carrying significant (over 10 kg) weights and requiring great physical effort.
When normalizing, two periods of the year are distinguished: cold(with an average daily outdoor temperature of +10 °С and below) and warm(with an average daily outdoor temperature above +10 °С).
In table. 1 shows the optimal (in parentheses - permissible) values of the microclimate parameters at permanent workplaces of industrial premises.
The intensity of thermal exposure is taken into account if there are heat sources in the production room heated to a high temperature.
Objective:
Get to know the complex meteorological conditions in industrial premises, with hygienic requirements (standards) for indicators of the microclimate of industrial premises and to master some methods for assessing indicators of meteorological conditions.
Work order:
- To study and outline general information about the complex of meteorological conditions at the workplace under item I.
- To study and outline information on methods for measuring microclimate indicators at the workplace under item II.
- Calculate according to the variant the value of the relative humidity at the workplace according to point III.
I General information
Terms and Definitions
Industrial premises - enclosed spaces in specially designed buildings and structures in which people work constantly (in shifts) or periodically (during the working day).
Workplace- a section of the premises where labor activity is carried out during the working shift or part of it. A workplace can be several sections of a production facility.
Cold period of the year - the period of the year, characterized by an average daily temperature of the outside air equal to + 10 ° C and below.
Warm period of the year - a period of the year characterized by an average daily outdoor temperature above +10 o C.
Average daily outdoor temperature - the average value of the outdoor air temperature, measured at certain hours of the day at regular intervals. It is taken according to the meteorological service.
- the combined effect on the human body of microclimate parameters (temperature, humidity, air velocity, thermal exposure), expressed as a single-number indicator in o C.General requirements and microclimate indicators
Sanitary rules establish hygienic requirements for the indicators of the microclimate of workplaces in industrial premises, taking into account the intensity of energy consumption of workers, the time of work, periods of the year, and contain requirements for methods for measuring and controlling microclimatic conditions.
Microclimate indicators should ensure the preservation of the thermal balance of a person with the environment and the maintenance of an optimal or acceptable thermal state organism.
The complex of meteorological conditions (microclimate) in industrial premises is the climate of the internal environment of these premises.
The indicators characterizing the microclimate in industrial premises are:
- air temperature t air, o C;
- surface temperature (walls, floors, ceilings, screens, process equipment or enclosing devices) t pov, o C;
- relative air humidity f, %;
- air velocity v, m/s;
- the intensity of thermal exposure T region, W/m 2 .
The values of the microclimate parameters in the production room depend on a number of factors: the climatic zone and the season of the year, the nature of the technological process and the type of equipment used, the air exchange conditions, the size of the room, the number of employees, etc. Some microclimate indicators (air temperature and infrared radiation intensity) may vary by throughout the shift or vary in separate sections of the same workshop.
In connection with these circumstances, the following types of microclimates (classification) are distinguished: a) comfortable; b) with high humidity, at normal, low and high air temperatures; c) variable (when working outdoors); d) heating with a predominance of radiative heat and with a predominance of convection heat; e) cooling with subnormal air temperatures (from +10 to -10 o C) and low air temperatures (below -10 o C).
Brief description of microclimate indicators
Air temperature - the degree of its heating, expressed in degrees. High air temperature is observed in rooms where technological processes are accompanied by significant heat release. Low air temperature occurs when working outdoors in winter and during transitional periods of the year or when servicing artificially cooled rooms.
Air humidity - the content of water vapor in it. There are: absolute humidity, which is expressed by water vapor pressure (Pa) or in weight units in a certain volume of air (g / m 3), maximum humidity (g / m 3) is the amount of moisture when the air is completely saturated at a given temperature, relative humidity - this is the ratio of absolute humidity to maximum, expressed as a percentage.
Air movement (m / s) is created as a result of a temperature difference or a pressure difference in adjacent areas of the room, when cold air flows from the outside due to work ventilation system, as well as when moving machines, units, people. The movement of air in a hot room helps to increase heat transfer from the body and improve well-being. However, it is unfavorable in the cold season. The speed of air movement also affects the distribution of harmful substances in the room (spread throughout the room, etc.) or raises dust, thereby deteriorating air quality.
Thermal radiation (infrared radiation) - this is electromagnetic radiation with a wavelength from 0.76 to 500 microns. The intensity of thermal radiation is expressed in J / (cm 2 .min) or in W / m 2 (Watt / m 2).
The effect of microclimate indicators on the body
Excessive heat and moisture release, as well as high air mobility worsen the microclimate of industrial premises, complicate thermoregulation, adversely affect the body of workers and contribute to a decrease in productivity and quality of work.
Despite the fact that the indicators that determine the microclimate in the room can vary significantly (within the permissible range), the temperature of the human body remains, as a rule, constant.
The body's ability to maintain heat balance is called thermoregulation. When the ambient temperature drops, there are restrictions on heat transfer by the body, which reduces blood flow to the body. skin and reduces skin moisture. When the air temperature rises, the reverse processes occur. In heat exchange processes, heat transfer mechanisms play a leading role.
Under normal microclimatic conditions, heat transfer by the body is carried out mainly due to radiation, which accounts for about 45% of all removed heat, to a lesser extent due to convection (heat transfer by air particles) - 30% and evaporation - 25%. At a low ambient temperature, the contribution of convection-radiation heat loss by the body increases, and at an elevated temperature, evaporation. At an ambient temperature equal to body temperature, the only way for the body to release heat is to evaporate sweat. Heat dissipation by evaporation of sweat depends on the relative humidity and the velocity of the surrounding air.
An integral indicator of the thermal state of the human body is body temperature. The degree of thermoregulation tension and the thermal state of the body are judged by changes in skin temperature and thermal balance. indirect indicators thermal state can serve as moisture loss and reaction of cardio-vascular system(heart rate, blood pressure, etc.). The persistent tension of thermoregulation due to constant overheating or hypothermia of the body contributes to the development of certain diseases.
In conditions of a heating microclimate, the restriction of heat transfer can lead to overheating of the body. This condition is characterized by an increase in body temperature, increased heart rate, profuse sweating, and in case of very strong overheating - heat stroke - loss of strength, impaired coordination of movements, drop in blood pressure, loss of consciousness, convulsions.
When working outdoors, as a result of intense solar radiation to the head, sunstroke is possible. It is manifested by headache, blurred vision, vomiting, convulsions, but at normal body temperature.
Under the influence of infrared radiation, both local (increased skin temperature, clouding of the lens - cataract) and general changes (disturbances in the functions of the cardiovascular and nervous systems) occur. Infrared radiant heat, in addition to direct impact on workers, heats the surrounding structures (floor, walls, equipment), increases the temperature inside the room, thereby worsening working conditions.
Optimal microclimate conditions
Microclimatic conditions under which there are no unpleasant sensations and tension of the thermoregulation system are called optimal.
They provide a general and local feeling of comfort during an 8-hour work shift with minimal stress on thermoregulatory mechanisms, do not cause deviations in health status, create prerequisites for a high level of performance and are preferred in the workplace.
The optimal parameters of the microclimate at the workplace should correspond to the values given in Table 1, in relation to the performance of work of various categories in the cold and warm periods of the year.
Changes in air temperature along the height and horizontally, as well as changes in air temperature during the shift, while ensuring optimal microclimate values at workplaces, should not exceed 2 ° C and go beyond the values \u200b\u200bspecified in Table 1 for certain categories of work.
In those cases when, due to technological requirements, technical and economic reasons, optimal norms cannot be provided, then the permissible values of the microclimate indicators are established.
Permissible microclimatic conditions are established according to the criteria for the permissible thermal and functional state of a person for the period of an 8-hour work shift. They do not cause damage or health problems, but can lead to general and local discomfort, tension in the mechanisms of thermoregulation, deterioration of well-being and decreased performance.
Table 1. Optimal values of microclimate indicators at the workplaces of industrial premises
| Period of the year | Category of work according to the level of energy consumption, W | Air temperature, o C | Surface temperature, С | Relative humidity, % | |
| cold | Ia (up to 139) Ib (140-174) IIa (175-232) IIb (233-290) III (more than 290) |
22-24 21-23 19-21 17-19 16-18 |
21-25 20-24 18-22 16-20 15-19 |
60-40 60-40 60-40 60-40 60-40 |
0,1 0,1 0,2 0,2 0,3 |
| warm | Ia (up to 139) Ib (140-174) IIa (175-232) IIb (233-290) III (more than 290) |
23-25 22-24 20-22 19-21 18-20 |
22-26 21-25 19-23 18-22 17-21 |
60-40 60-40 60-40 60-40 60-40 |
0,1 0,1 0,2 0,2 0,3 |
Permissible values of microclimate indicators at workplaces must correspond to the values given in Table 2 in relation to the performance of work of various categories in the cold and warm periods of the year. When ensuring acceptable microclimate values at workplaces:
- the difference in air temperature along the height should be no more than 3 ° C;
- horizontal air temperature difference, as well as its changes during the shift, should not exceed:
In this case, the absolute values of air temperature should not go beyond the values indicated in Table 2 for certain categories of work. At an air temperature at workplaces of 25 ° C and above, the maximum allowable values of relative air humidity should not go beyond:
- 70% - at an air temperature of 25 ° C;
- 65% - at an air temperature of 26 ° C;
- 60% - at an air temperature of 27 ° C;
- 55% - at an air temperature of 28 ° C.
At an air temperature of 26-28 ° C, the air velocity indicated in Table 2 for the warm period of the year should correspond to the range:
- 0.1 - 0.2 m/s - for work category Ia;
- 0.1 - 0.3 m/s - for work category Ib;
- 0.2 - 0.4 m / s - for the category of work IIa;
- 0.2 - 0.5 m / s - for work categories IIb and III.
Intensity of thermal irradiation of process equipment working from heated surfaces, lighting fixtures, insolation at permanent and non-permanent workplaces should not exceed 35 W / m 2 with irradiation of 50% of the body surface or more, 70 W / m 2 - with an irradiated surface of 25 to 50% and 100 W / m 2 - with irradiation not more than 25% of the body surface.
The intensity of thermal exposure of workers from open sources (heated metal, glass, "open" flame, etc.) should not exceed 140 W / m 2, while more than 25% of the body surface should not be exposed to radiation and it is mandatory to use personal protective equipment, in including face and eye protection.
II. Requirements for methods of measurement and control of microclimate indicators
Measurements of microclimate indicators in order to control their compliance hygiene requirements should be carried out in the cold season - on days with an outside temperature that differs from average temperature the coldest month of winter by no more than 5 ° C, in the warm period of the year - on days with an outside air temperature that differs from the average maximum temperature of the hottest month by no more than 5 ° C. The frequency of measurements in both periods of the year is determined by the stability of the production process , the functioning of technological and sanitary equipment.
When choosing sites and measurement time, it is necessary to take into account all factors affecting the microclimate of workplaces (phases of the technological process, the functioning of ventilation and heating systems, etc.). Measurements of microclimate indicators should be carried out at least 3 times per shift (at the beginning, in the middle and at the end). With fluctuations in microclimate indicators associated with technological and other reasons, it is necessary to carry out additional measurements at the highest and lowest values of thermal loads on workers.
In the presence of sources of local heat release, cooling or moisture release, measurements should be carried out at each workplace at points that are minimally and maximally remote from thermal impact sources.
For work performed while sitting, the temperature and air velocity should be measured at a height of 0.1 and 1.0 m, and the relative humidity of the air - at a height of 1.0 m from the floor or work platform. For work performed while standing, the temperature and air velocity should be measured at a height of 0.1 and 1.5 m, and the relative humidity of the air at a height of 1.5 m.
Table 2. Permissible values of microclimate indicators at workplaces of industrial premises
| Period of the year | Category of work by the level of energy consumption, W | Air temperature, o C | Surface temperature, °C | Relative humidity, % | Air speed, m/s | ||
| range below optimal values | range above optimal values | for the range of air temperatures below the optimum values, no more | for the air temperature range above the optimal values, no more | ||||
| Cold | Ia (up to 139) Ib (14О-174) IIa (175-232) IIb (233-29O) III (more than 29O) |
20,0-21,9 19,0-20,9 17,0-18,9 15,0-16,9 13,0-15,9 |
24,1-25,0 23,1-24,0 21,1-23,0 19,1-22,0 18,1-21,0 |
19,0-26,0 18,0-25,0 16,0-24,0 14,0-23,0 12,0-22,0 |
15-75 15-75 15-75 15-75 15-75 |
0,1 0,1 0,1 0,2 0,2 |
0,1 0,2 0,3 0,4 0,4 |
| Warm | Ia (up to 139) Ib (14О-174) IIa (175-232) IIb (233-29O) III (more than 29O) |
21,0-22,9 20,0-21,9 18,0-19,9 16,0-18,9 15,0-17,9 |
25,1-28,0 24,1-28,0 22,1-27,0 21,1-27,0 20,1-26,0 |
20,0-29,0 19,0-29,0 17,0-28,0 15,0-28,0 14,0-27,0 |
15-75 15-75 15-75 15-75 15-75 |
0,1 0,1 0,1 0,2 0,2 |
0,2 0,3 0,4 0,5 0,5 |
In the presence of sources of radiant heat, thermal exposure at the workplace must be measured from each source, placing the receiver of the device perpendicular to the incident flow. Measurements should be carried out at a height of 0.5, 1.0 and 1.5 m from the floor or working platform.
The temperature of surfaces should be measured in cases where workplaces are removed from them at a distance of no more than two meters.
The temperature of each surface is measured in the same way as air temperature measurement.
Based on the results of the study, it is necessary to draw up a protocol and evaluate the results for compliance with regulatory requirements.
Air temperature and relative humidity should be measured with stationary or aspiration psychrometers (Fig. 1 and Fig. 2).
The speed of air movement is measured with vane or cup anemometers (Fig. 5 and Fig. 6), and small values of air velocity (less than 0.3 m/s) are measured with cylindrical or spherical catathermometers.
Thermal exposure, the temperature of the surfaces of structures (walls, floors, ceilings) or devices should be measured with an actinometer or an electrothermometer.
The measurement of air temperature in industrial premises is usually combined with the determination of humidity and is carried out using a dry thermometer of a psychrometer.
Elective determination of air temperature may be required for some special studies, for example, when taking air samples for chemical analysis or in cases where the measured air temperature exceeds the limits of the psychrometer scale (45-50 ° C). In these cases, ordinary mercury thermometers with a scale of 100 ° C are used.
To measure the air temperature in the presence of thermal radiation, a paired thermometer is used (Fig. 3). The device consists of two mercury thermometers with a scale of 100 ° C. The surface of the mercury tank of one of them is blackened, the other is silver plated. The first one absorbs the radiant energy falling on it, heats up with it, and therefore its readings are overestimated. The second thermometer mainly reflects radiation. Its readings mainly display the air temperature. However, this thermometer also partially absorbs the rays falling on it and also slightly overestimates the readings of the thermometer. In this regard, the true air temperature is calculated by the empirical formula:
, (1)
where t and - true temperature;
t B - readings of a thermometer with a silver-plated tank;
t T - readings of a thermometer with a black tank;
k - constant of this device (according to the passport), usually - within 0.10 - 0.12.
Table 3. Initial data for the tasks of calculating the relative humidity of the air
| Options | Options | |||||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
| Dry bulb temperature, dry t (o C) | 21 | 24 | 26 | 24 | 25 | 27 | 22 | 22 | 24 | 24 |
| Wet bulb temperature, t in (o C) | 18 | 20 | 21 | 21 | 21 | 22 | 19 | 18 | 19 | 20 |
| Barometric pressure H, mm Hg | 760 | 755 | 750 | 745 | 740 | 765 | 763 | 757 | 767 | 770 |
| Air velocity, v (m/s) | 0,01 | 0,06 | 0,08 | 0,10 | 0,13 | 0,16 | 0,20 | 0,30 | 0,40 | 0,80 |
| Relative humidity, f(%) - ? | ||||||||||
Measurement of relative air humidity with a stationary psychrometer
A stationary psychrometer (Fig. 1) is a device consisting of two identical thermometers located side by side with a scale of 50 ° C. The reservoir of one of them is wrapped in a piece of thin cloth and lowered into a glass of water.
Measurements using this device are made within 10-15 minutes until the mercury (or alcohol) columns in both thermometers stabilize at a constant level.
When using a stationary psychrometer, the relative humidity is determined in the following order. First, based on the readings of the wet thermometer, the absolute humidity is calculated, which is calculated by formula (2):
, (2)
where A is absolute humidity, mm Hg. Art.;
F 2 - water vapor pressure (Table 4, take intermediate data using interpolation) at wet bulb temperature, mm Hg. Art.;
Psychrometric coefficient (Table 3);
t c - dry thermometer readings, o C;
t in - wet thermometer readings, o C;
H - barometric pressure, mm Hg. Art.
The value of the psychrometric coefficient "" depends on the speed of air movement and for this speed there is a constant value (Table 3). It is known that the readings of a stationary psychrometer become more accurate if some air movement is provided around it. To do this, when measuring the temperature with a stationary psychrometer, an air movement (0.8 m/s) is created near the device by slowly waving the book for 4-5 minutes.
The aneroid barometer scale (Fig. 4) is graduated in pascals, while formula (2) requires the unit of barometric pressure, expressed in mm Hg. Art. The ratio between these indicators is as follows: 1 mm Hg = 133.32 pascals (Pa).
For example, 101,070 Pa: 133.32 = 749 mm Hg. Art.
Relative humidity determined by the formula:
, (3)
where f is the desired relative humidity,%;
A - absolute humidity, mm Hg. Art.;
F 1 - saturated vapor pressure, mm Hg. Art. at the temperature indicated by a dry thermometer (see Table 4).
Determination of relative humidity with an aspiration psychrometer
An aspiration psychrometer (Fig. 2) is more reliable, more accurate and more convenient to use than a stationary one, although they have the same basic device. In an aspiration psychrometer, the thermometers are enclosed in a metal frame, which protects them from mechanical damage. The thermometer reservoirs are housed inside double metal cylinders that protect against both shock and radiant heat. The device is equipped with a microfan with a clock mechanism, which provides air blowing of the thermometer reservoirs at a constant speed (4 m/s). In this regard, the time required for the measurement is reduced to 3-5 minutes and the formula for calculating absolute humidity is greatly simplified:
test questions
- What criteria are set sanitary rules for Russian citizens?
- What act is considered a sanitary offense?
- What types of liability are provided for by the Law on Sanitary and Epidemiological Welfare of the Russian Federation for persons who have committed a sanitary offense?
- What is a production facility?
- What workplace?
- What is the cold season?
- What is the warm season?
- What is the average daily outdoor temperature?
- What categories of work are distinguished by the total energy expenditure of the body?
- What is the microclimate in industrial premises?
- What parameters make up the microclimate of the working premises?
- What is the main requirement for microclimate parameters in industrial premises?
- What conditions affect the value of microclimate parameters?
- What types of microclimates (classification) are distinguished?
- What is air temperature?
- What is air humidity?
- What is absolute humidity and in what units is it measured?
- What is maximum humidity and in what units is it measured?
- What is relative humidity and in what units is it measured?
- What is air movement in work areas and why does it occur?
- What is thermal radiation and in what units is it measured?
- How do excessive values of microclimate parameters affect a person?
- What is thermoregulation?
- What are the mechanisms by which heat is transferred from the body?
- What integral indicator is used to evaluate the thermal state of an organism?
- What complications arise when heat transfer is disturbed by the body?
- What is the difference between heatstroke and sunstroke?
- What are the limits of microclimate parameters?
- What is the optimal value of the microclimate parameter?
- What can be the temperature difference while ensuring its optimal level?
- What is the permissible value of the microclimate parameter?
- At what value does the microclimate parameter become harmful or dangerous?
- What can be the temperature drop while ensuring its acceptable level at the workplace?
- What is the permissible value of relative humidity in the workplace?
- What is the acceptable air velocity in the workplace?
- What is the permissible intensity of thermal radiation in the workplace?
- What are the main requirements for methods of measurement and control of microclimate parameters?
- What instruments are used to measure the microclimate parameters in the workplace?
- How is the true temperature in the workplace estimated?
- What microclimate parameter is measured by a stationary psychrometer and how does this device work?
- How is the accuracy of the readings of a stationary psychrometer improved?
- What formula is used to determine the absolute humidity of the air when using a stationary psychrometer?
- What is the formula for determining relative humidity?
- What formula is used to determine relative humidity when using an aspiration psychrometer?
In the process of labor in a production room, a person is in a state of thermal interaction with the environment, which depends on certain meteorological conditions, or microclimate - the climate of the internal environment of these premises. The air of the working area is the air environment in a space up to 2 m above the floor or platform where the workplaces are located.
The main share in the process of removing heat from the human body (about 90% of the total amount of heat) is contributed by radiation, convection and evaporation.
Heat transfer by convection depends on the air temperature in the room and its speed in the workplace, and heat transfer by evaporation depends on relative humidity and air speed.
To the main normalized indicators of air microclimate working area relate:
temperature (t, 0 FROM),
relative humidity (φ, %),
air speed (V, m/s).
The intensity of thermal radiation (I, W / m 2) of various heated surfaces, the temperature of which exceeds the temperature in the production room, also has a significant impact on the parameters of the microclimate 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 D (g / m 3) to the amount of water vapor saturating the air at this temperature, D o (g / m 3): φ \u003d D / D o. 100%.
If there are various heat sources in the production room, the temperature of which exceeds the temperature of the human body, then the heat from them spontaneously passes to a less heated body, i.e. to a person.
The heat entering the production room from various sources affects the air temperature in it. In industrial premises with high heat release, approximately 2/3 of the heat comes from radiation, and almost all the rest comes from convection.
The source of thermal radiation in production conditions is molten or heated metal, an open flame, heated equipment surfaces.
In domestic regulations the concepts of optimal and permissible microclimate parameters are introduced.
Optimal microclimatic conditions are such combinations of quantitative parameters of the microclimate that, with prolonged and systematic exposure to a person, ensure the preservation of the normal functional and thermal state of the body without straining the mechanisms of thermoregulation. They provide a sense of thermal comfort and create the prerequisites for a high level of performance and are preferred in workplaces.
Permissible conditions are such combinations of quantitative parameters of the microclimate, which, with prolonged and systematic exposure to a person, can cause tension in the reactions of thermoregulation, and which do not go beyond the limits of physiological adaptive capabilities. In this case, there are no violations in the state of health, but uncomfortable heat sensations are observed that worsen well-being and reduce efficiency.
In GOST 12. 1.005-88 “Air of the working area. General sanitary and hygienic requirements" the optimal and permissible parameters of the microclimate in the production room are presented, depending on the severity of the work performed, the amount of excess heat in the room and the season (season).
In accordance with this GOST, there are cold and transitional periods of the year (with an average daily outdoor temperature below + 10 ° C), as well as a warm period of the year (with a temperature of + 10 ° C and above).
The physical burden of work determined by energy costs in the process labor activity and is divided into the following categories: light, moderate and heavy physical work.
light physical work(category I) are divided into two subcategories: Ia, in which energy consumption is up to 139 W, work carried out while sitting and accompanied by little physical effort; I 6, at which energy consumption is 140-174 W, work performed while sitting, standing or walking and accompanied by some physical effort.
Physical work of moderate severity(category II) are also divided into two subcategories: IIa, in which energy consumption is 175-232 W, work associated with constant walking, moving small (up to 1 kg) products or objects in a standing or sitting position and requiring certain physical effort; II 6, at which energy consumption is 233-290 W, work associated with walking, moving and carrying loads weighing up to 10 kg and accompanied by moderate physical effort.
Heavy physical work(category III) are characterized by an energy consumption of more than 290 W. This category includes work associated with constant movement, movement and transfer of significant (over 10 kg) weights and requiring great physical effort.
Microclimate parameters in industrial premises are controlled by various control and measuring devices.
To measure the air temperature in industrial premises, mercury (to measure temperatures above 0 ° C) and alcohol (to measure temperatures below 0 ° C) are used. thermometers.
If constant recording of temperature changes over time is required, devices called thermographs. For example, a domestic device - a thermograph of the M-16 type - registers temperature changes over a certain period (day or week). There are other devices for measuring air temperature, such as thermocouples.
For measuring relative humidity air, devices called psychrometers and hygrometers, and a hygrograph is used to register the change in this parameter over time.
The simplest psychrometer is a device consisting of dry and wet bulbs. At the wet bulb thermometer, the tank is wrapped with an hygroscopic cloth, the end of which is lowered into a glass of distilled water. A dry thermometer shows the temperature of the air in the production room, and a wet thermometer shows a lower temperature, since water evaporating from the surface of a damp cloth takes away heat from the thermometer reservoir.
There are special conversion psychrometric tables that allow you to determine the relative humidity of the air in the room using the temperatures of dry and wet thermometers.
More complex in design, but also more accurate is the so-called aspiration psychrometer, which also consists of dry and wet thermometers placed in metal tubes and blown with air at a speed of 3-4 m / s, as a result of which the stability of thermometer readings increases and the effect of thermal radiation is practically eliminated. Relative humidity is also determined using psychrometric tables.
Aspiration psychrometers, such as MV-4M or M-34, can be used to simultaneously measure indoor air temperature and relative humidity.
Another device for determining relative humidity is hygrometer, the action of which is based on the property of some organic substances (organic membranes, human hair) to lengthen in humid air and shorten in dry air. By measuring the deformation of the sensitive element (membrane or hair), one can judge the relative humidity in the production room. Hygrographs record changes in relative humidity as a function of time.
The speed of air movement in the production room is measured by devices - anemometers.
The operation of a vane anemometer is based on changing the rotation speed of a special wheel equipped with aluminum wings located at an angle of 45° to the plane perpendicular to the axis of rotation of the wheel. The wheel axle is connected to the rev counter. When the speed of the air flow changes, the speed of rotation of the wheel also changes, i.e., the number of revolutions increases (decreases) for a certain period of time. From this information, the airflow rate can be determined. Vane anemometers are recommended to be used to measure the air flow velocity in the range of 0.4-10 m/s; at speeds of 1-35 m/s, cup anemometers are used in which the wings are replaced by cups. An example of a vane anemometer is the device ASO-3 type B, a cup anemometer is type MS-13.
There are other devices for measuring the speed of air movement: spherical or cylindrical catathermometers and hot-wire anemometers.
The intensity of thermal radiation in domestic practice is measured actinometers, the action of which is based on the absorption of thermal radiation and the registration of the released thermal energy.
The simplest thermal receiver - thermocouple. It is an electrical circuit of two wires made of various materials(both metals and semiconductors), e.g. copper-constantan, silver-palladium, silver-bismuth, bismuth-antimony, tungsten-rhenium, etc..
Two wires of different materials are welded or soldered together. Thermal radiation heats one of the junctions of the two wires, while the other junction serves for comparison and is maintained at a constant temperature (T o). Under the influence of a temperature difference, a thermo-EMF arises, which is measured by a sensitive device calibrated in degrees of the corresponding scale.
When microclimate parameters deviate from values that create comfortable conditions, it is of great importance the right choice of clothing. When working in rooms with low air temperature, it is necessary to use insulated overalls. For personnel employed in hot shops, use overalls made from materials with low thermal conductivity.
To maintain normal microclimate parameters in the working area the following main steps are taken:
mechanization and automation of technological processes,
protection from sources of thermal radiation,
installation of ventilation systems,
air conditioning and heating.
In addition, it is important to properly organize the work and rest of workers performing labor-intensive work or work in hot shops.
Mechanization and automation the production process can either drastically reduce the labor load on workers (the mass of the load lifted and moved manually, the distance of movement of the load, reduce transitions due to the technological process, etc.), or completely remove a person from the production environment, shifting his labor functions to automated machines and equipment. However, the automation of technological processes requires significant economic costs, which makes it difficult to introduce these measures into production practice.
For protection against thermal radiation use different thermal insulation materials, arrange heat shields and special ventilation systems (air showering). The listed means of protection are a generalizing concept of heat-shielding means. Thermal protective equipment must ensure thermal irradiance at workplaces of not more than 350 W / m 2 and the surface temperature of the equipment is not higher than 35 ° C at a temperature inside the heat source up to 100 ° C and not higher than 45 ° C - at a temperature inside the heat source above 100 ° C .
The main indicator characterizing the effectiveness of thermal insulation materials is the low coefficient of thermal conductivity, which for most of them is 0.025-0.2 W/m. TO.
The coefficient of thermal conductivity or thermal conductivity (λ) shows how much heat passes due to thermal conductivity per unit time through a unit wall area with a temperature difference between the wall surfaces of one degree. In the SI system, the dimension is λ W/m.K.
Various materials are used for thermal insulation, for example, asbestos cloth and cardboard, special concrete and brick, mineral and slag wool, fiberglass, carbon felt, etc.
Thus, mineral wool materials can be used as thermal insulation materials for steam and hot water pipelines, as well as for cold supply pipelines used in industrial refrigerators.
Heat shields are used to localize sources of thermal radiation, reduce exposure to workplaces, and also to reduce the temperature of surfaces surrounding the workplace. Screens reflect some of the thermal radiation, and absorb some.
To quantify the protective effect of the screen, the following indicators are used: the heat flux attenuation factor (m), as well as the efficiency of the screen (η e).
These characteristics are expressed by the following dependencies:
m \u003d E 1 / E 2 and η e \u003d (E 1 - E 2). 100% / E 1
where E 1 and E 2 - the intensity of thermal exposure at the workplace, respectively, before and after the installation of screens, W / m 2,
The indicator m determines how many times the initial heat flux at the workplace exceeded the heat flux at the workplace after installing the screen, and the indicator η e - what part of the initial heat flux reaches the workplace protected by the screen. Efficiency η e for most screens is in the range of 50-98.8%.
There are heat-reflecting, heat-absorbing and heat-removing screens.
Heat-reflecting screens are made of aluminum or steel, as well as foil or mesh based on them. Heat-absorbing screens are structures made of refractory bricks (chamotte type), asbestos cardboard or glass (transparent screens). Heat shields are hollow structures cooled from the inside by water.
A kind of heat-removing transparent screen is the so-called water curtain, which is arranged at the technological openings of industrial furnaces and through which tools, processed materials, workpieces, etc. are introduced into the furnaces.
3. The concept of microclimate, its parameters.
The microclimate of industrial premises is the microclimatic conditions of the industrial environment (temperature, humidity, pressure, air velocity, thermal radiation) of premises that affect the thermal stability of the human body in the process of work.
Studies have shown that a person can live at an atmospheric pressure of 560-950 mmHg. Atmosphere pressure at sea level 760 mmHg. With this pressure, a person experiences comfort. Both an increase and a decrease in atmospheric pressure have a negative effect on most people. With a decrease in pressure below 700 mmHg, oxygen starvation occurs, which affects the functioning of the brain and central nervous system.
3.1 General requirements for microclimate parameters
Microclimate parameters in accordance with GOST 12.1.005-88 and SanPiN 2.2.4. 548-96 must ensure the preservation of the thermal balance of a person with the surrounding production environment and the maintenance of an optimal or acceptable thermal state of the body.
The parameters characterizing the microclimate in industrial premises are:
Air temperature, t˚C
Temperature of surfaces (walls, ceiling, floor, equipment enclosures, etc.), tp ˚C
Relative air humidity, W %
Air velocity, V m/s
The intensity of thermal exposure, P W / m 2
Absolute humidity A is the amount of water vapor contained in 1 m3. air. Maximum humidity F max - the amount of water vapor (in kg), which completely saturates 1 m3 of air at a given temperature (water vapor pressure).
Relative humidity is the ratio of absolute humidity to maximum humidity, expressed as a percentage:
When the air is completely saturated with water vapor, i.e. A=Fmax (during fog), the relative humidity of the air φ =100%.
The average temperature of all surfaces limiting the room also influences the human body and the conditions of its work; it is of great hygienic importance.
Another important parameter is the speed of air movement. At elevated temperatures, the air velocity contributes to cooling, and at low temperatures to supercooling, so it should be limited, depending on the temperature environment.
Sanitary - hygienic, meteorological and microclimatic conditions not only affect the state of the body, but also determine the organization of work, that is, the duration and frequency of the worker's 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.
3.2 Thermoregulation of the body
One of necessary conditions normal human life is to ensure normal meteorological conditions in the premises, which have a great impact on the thermal well-being of a person. Meteorological conditions, or microclimate, depend on the thermophysical features of the technological process, local climate, season, heating conditions (during the cold season) and ventilation in the premises.
Human labor activity is accompanied by a continuous release of heat into the environment. Its amount depends on the degree of physical stress in certain climatic conditions and ranges from 85 W (at rest) to 500 W (during hard work). In order for the physiological processes in the body to proceed normally, the heat released by the body must be completely removed to the environment. Violation of the thermal balance can lead to overheating or hypothermia of the body and, as a result, to loss of efficiency, fatigue, loss of consciousness, accidents and occupational diseases.
Normal thermal well-being takes place when the heat release of a person Qtch is completely perceived by the environment Qts, i.e. when there is a thermal balance Qtch = Qts, then in this case the temperature of the internal organs remains constant at 36.5 ˚C.
If the body's heat production cannot be fully transferred to the environment (Qtch>Qts), the temperature of the internal organs rises and such a thermal well-being is characterized by the concept hot . The thermal insulation of a person (for example, in warm and dense clothes), who is at rest (sitting or lying down) from the environment, will lead to an increase in his temperature by 1.2˚C already after 1 hour. And the same when performing work of medium severity, will cause an increase in temperature by 5 ˚C, i.e. will approach the critical (+43˚C) temperature.
In case when environment perceives more heat than it is produced by a person (Qtch
Thermoregulation of the body- the physiological process of maintaining body temperature in the range from 36.6 to 37.2 ° C. The main way to maintain equilibrium is heat transfer.
Heat transfer proceeds in the following ways:
1 . heat radiation(Q izl) by the human body in relation to surrounding surfaces that have a lower temperature. This is the main way of heat transfer in production conditions. All bodies that have a temperature above absolute zero - 273 ° C give off heat by radiation. A person gives off heat when the temperature of the surrounding objects is lower than the temperature of the outer layers of clothing (27 - 28 ° C) or open skin.
2. Holding(Q p) - heat transfer to objects in direct contact with the human body.
3. Convection(Q to) - heat transfer through the air. A person heats up a layer of air around him with a thickness of 4 - 8 mm by conducting heat. The heating of more distant layers occurs due to the natural and forced replacement of the warmer layers of air adjacent to the body by colder ones. With moving air, heat transfer increases several times.
4. Evaporation of water from the surface of the skin and mucous membrane of the upper respiratory tract(Q is.) - the main way of heat transfer at elevated air temperature, especially when the return of radiation or convection is difficult or stops. Under normal conditions, evaporation occurs as a result of imperceptible sweating on most of the body surface as a result of water diffusion without the active participation of the sweat glands. In general, the body loses 0.6 liters of water per day. When performing physical work in conditions of high air temperature, there is increased sweating, in which the amount of fluid lost is 10-12 liters per shift. If the sweat does not have time to evaporate, it covers the skin with a moist layer, which does not contribute to heat transfer, and conditions are created for the body to overheat. In this case, there is a loss of water and salts. This leads to dehydration of the body, loss of mineral salts and water-soluble vitamins (C, B1, B2). Such loss of moisture leads to thickening of the blood, a violation of salt metabolism.
During hard work in conditions of high air temperature, 30-40 g of NaCl salt is lost (in total, 140 g of NaCl in the body). Further loss of salts causes muscle spasms, convulsions.
5. Thermal (infrared) radiation. Under production conditions, thermal (infrared) radiation - invisible electromagnetic radiation - may be present. Source - any heated body.
Depending on the wavelength, it is divided into short-wave, medium-wave, long-wave. Passing through the air, these rays do not heat it, but, being absorbed by a solid body, the radiant energy passes into heat.
Features of the action of radiant heat depend on the wavelength of infrared radiation. Long waves (1.4 - 10 microns) are absorbed by the skin layer, causing a glowing effect. Short waves penetrate deep into the body, heating the internal organs, brain, blood. Prolonged exposure to elevated temperatures combined with high humidity can lead to overheating of the body. In this case, a person has a headache, nausea, palpitations, general weakness, vomiting, sweating, rapid breathing, tachycardia. When working in air, as a result of irradiation of the head with infrared rays of the short-wave range, severe damage to the brain tissue occurs, up to severe meningitis and encephalitis. In severe cases, convulsions, delirium, loss of consciousness are observed. At the same time, body temperature remains normal or rises slightly.
Normal heat transfer (i.e. thermal comfort) occurs when
Q tch \u003d Q to + Q t + Q izl + Q isp + Q in \u003d Q ts
With a significant excess of the heat production of the human body (Qtch»Qts) occurs overheat (hyperthermia), threatening human life and health; with a significant decrease in the body's heat production compared to the absorption capacity of the environment, there is hypothermia (hypothermia), dangerous to human health and life.
Under conditions of thermal homeostasis, the balance of heat in the body of homoiotherms is described by the expression:
ΔQ = M - E ± C ± R ± K ± W = 0
where ΔQ - changes in heat content; M is the production of heat, and the remaining members of the equation are the transfer of heat by the body to the external environment in various ways. Under conditions of thermal comfort ΔQ = 0.
Here it is immediately necessary to specify the essential modern understanding of homeostasis, according to which any of its types, including thermal homeostasis, is expressed not in the rigid fixation of certain indicators at a certain level, but rather in their fluctuation around the average value. This fundamental consideration, at least for a person, is also confirmed in fact - by the phenomenon of extreme instability of the heat exchange of the human body.
O. Barton and A. Edholm (1957) point out that even during short-term studies in special climatic chambers with strict control of meteorological conditions and the state of the examined, a thermostable state is not achieved for several hours. Expression 1 is a complete heat balance equation, but the evolutionary and biological significance of its components is far from the same. So, the production of heat in the body (M) is not genetically determined by heat exchange, but is a consequence of the fundamental processes that characterize life. A living organism is characterized by a continuous exchange of matter and energy, which occurs in accordance with the well-known equation of thermodynamics:
|
ΔН = ΔZ + TΔS |
where ΔH is the change in enthalpy - measures of the total supply of chemically converted energy; ΔZ - change in thermodynamic potential or free energy - part of the enthalpy of the system, which can be usefully used to do work; ΔS - changes in entropy (thermodynamic) for given conditions - a measure of the uncertainty of the system, depending on the action of intermolecular forces and thermal motion and measured by the dissipation of the potential energy of chemicals in the form of heat; T - °K (degrees Kelvin).
Thus, the source of heat production (M) is the processes of metabolism and energy that are continuously taking place in the body. In the course of the splitting of energy materials, the energy accumulated in high-energy compounds can be dissipated in the form of heat ("primary heat"), or converted into certain types of work, ultimately also turning into thermal energy. However, the body receives the main heat as a result of the implementation of certain types of work (70% of heat production), while heat dissipation is only 30%.
Table 3. 1. Oxygen consumption by various organs of an adult weighing 63 kg (Bord R., 1961)
|
Oxygen consumption by various organs of an adult weighing 63 kg (Bord R., 1961) |
|||||
|
Organ |
Weight, kg |
Arteriovenous oxygen difference, cm 3 /l |
Oxygen consumption |
||
|
absolute, cm 3 /min |
relative |
||||
|
cm 3 /(min 100 g) |
% of total |
||||
|
Skeletal muscles | |||||
|
Other parts of the body | |||||
|
body as a whole | |||||
For the problem of regulation of heat exchange, sources of heat production at rest and during muscular work are of significant interest. Heat generation is inextricably linked with energy metabolism. Under conditions of normal vitality at rest, the magnitude of heat production can be judged by the intensity of oxidative processes (oxygen consumption). The corresponding data are given in table. 3.1
At rest, the highest contribution to heat production (58.8%) is provided by the liver, brain and skeletal muscles. At the same time, in the first two organs, the relative indicators of energy metabolism are also high (arteriovenous difference in oxygen and its relative consumption by the organ); at the same time, the intensity of metabolism in resting muscles is low and the gross value of their heat production is determined simply by a significant mass of muscle tissue.
The structure of energy consumption in tissues (Ivanov K.P., 1972) shows that out of 1600 kcal / day (under conditions of basal metabolism), about 900 kcal is captured in the form of high-energy ATP bonds, 215 kcal is used to maintain non-equilibrium ionic concentrations on both sides of cell membranes , 415 kcal provides processes for the renewal of proteins, lipids and polysaccharides, and only 270 kcal is spent on contraction of the heart muscle and respiratory muscles. At the same time, all these processes are characterized by low efficiency values, for example, protein synthesis has an efficiency of 10-13%, ion transport - 20%, ATP synthesis - 50%, etc. Thus, there is an accumulation of "primary" and "secondary" heat .
When performing muscular work, the energy metabolism in the muscles increases sharply, which can be judged by such an indirect indicator as the value of the minute volume of blood flowing through the muscles at rest and during their contraction: in the first case it is 840 ml / min, and in the second - 12,500 ml/min, indicating an increase in muscle oxygen consumption by at least 5 times. Thus, the increase in heat production during muscular work is due to the increased generation of heat, primarily in the skeletal muscle tissue. However, one should also take into account an adequate increase in energy processes (and heat production) in the organs that provide muscle work - in the brain and spinal cord, heart, respiratory muscles, in the liver and other organs.
Under conditions of thermal comfort, voluntary muscle movements are of paramount importance in thermogenesis, because, as I. M. Sechenov (1863) brilliantly remarked, “all the infinite variety of external manifestations of brain activity” is reduced to them. Measurements of energy consumption during "ordinary" motor acts of a person show their different (sometimes significant) thermogenetic cost (Kandror IS, 1968).
Depending on human behavior, even over several hours, shifts in heat production can be in the nature of fast and significant peaks.
Microclimate parameters are regulated taking into account the severity of physical labor and the time of year.
A change in the microclimate parameters causes a change in the ratio of heat production Q. Thus, under normal conditions during light physical work, the share of Qc + Qt is about 30% of the total heat transfer, Qcd is about 45%, Qsp = 20% and Qv = 5%.
The higher the temperature of the surrounding objects, the lower the heat transfer by radiation. With an increase in the ambient temperature to the temperature of the human body and above, the efficiency of heat transfer by thermal conductivity Qt, convection Q and radiation Qi decreases and heat removal by evaporation of moisture (sweat) from the surface of the body Qisp becomes decisive. But the intensity of evaporation of moisture from the surface of the human body depends on the relative humidity W and the velocity of the surrounding air V.
At W more than 75%, the process of moisture evaporation slows down sharply, and at W=100% it stops completely. At the same time, heat transfer Qisp slows down, and then stops. With an increase in humidity, sweat does not evaporate, but flows in drops from the surface of the skin. There is a so-called "torrent" sweating, exhausting the body and does not create the necessary heat transfer. There is dehydration of the body, which entails a violation of visual acuity and mental activity. Loss of moisture by 15-20% leads to death.
Insufficient humidity (<20%) также оказывает неблагоприятное воздействие на организм, вследствие интенсивного испарения влаги со слизистых оболочек, их пересыхания, растрескивания и кровотечения.
An increase in air velocity υ always leads to an increase in heat transfer to the environment.
With light work, higher temperatures and lower air speeds are allowed.
During the warm period of the year (at an outdoor temperature of +10°C and above), the temperature in the production room should be no more than +28°C for light work and no more than +26°C for hard work. If the outside temperature is more than +25°C, then the room temperature may rise to +33°C.
According to DSN 3.3.6 042-99 "Sanitary norms 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 industrial premises, optimal and permissible microclimatic conditions are established, taking into account the severity of the work performed and the period of the year (Table 3.2).
Optimal microclimatic conditions are such microclimate conditions that, with prolonged and systematic influence on a person, ensure the preservation of the thermal state of the body without the active work of thermoregulation. They maintain the well-being of thermal comfort and the creation of a high level of labor productivity (Table 3.2.).
Permissible microclimatic conditions that, with prolonged 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 3.2.). In this case, there are no violations or deterioration in health, but there is an uncomfortable heat perception, deterioration in well-being and a decrease in working capacity.
Microclimate conditions that go beyond the permissible limits are called critical and lead, as a rule, to serious disturbances in the state of the human body.
Optimal microclimate conditions are created for permanent jobs.
Table 3.2
Optimal values of temperature, relative humidity and air velocity in the working area of industrial premises.
|
Period of the year |
Air temperature, 0 С |
Relative humidity, % |
Travel speed, m/s |
|
|
Cold period of the year |
Easy I-a | |||
|
Light I-b | ||||
|
Moderate II-a | ||||
|
Moderate II-b | ||||
|
Heavy III | ||||
|
Warm period of the year |
Easy I-a | |||
|
Light I-b | ||||
|
Moderate II-a | ||||
|
Moderate II-b | ||||
|
Heavy III |
Permissible values of microclimatic conditions are established in the case when it is not possible to provide 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 allowable temperatures of the categories of work.
The external environment surrounding a person at work affects the human body, its physiological functions, psyche, and labor productivity.
