Lung ventilation and lung volumes The value of lung ventilation is determined by the depth of breathing and the frequency of respiratory movements. The quantitative characteristic of lung ventilation is the minute respiratory volume (MOD) - the volume of air passing through the lungs in 1 minute.

Ventilation is an organized air exchange, during which dusty, gas-polluted or highly heated air is removed from the room and fresh, clean air is supplied instead.

The ventilation system is a complex of architectural, structural and special engineering solutions, which, when correct operation provides the necessary air exchange in the room.

The ventilation system is engineering design, which has a certain functional purpose(supply, exhaust, local suction, etc.) and is an element of the ventilation system.

Ventilation systems create conditions for ensuring the technological process or maintaining the predetermined climatic conditions for highly productive work. In the first case, the ventilation system will be called technological, and in the second - comfortable.

Technological ventilation provides the room with a given composition of air, its temperature, humidity, and mobility in accordance with the requirements of the technological process. These requirements are especially high in the workshops of such industries as the radio engineering, electrovacuum, textile, chemical and pharmaceutical industries, storage facilities for agricultural products, archives, and premises in which historical values ​​are stored.

Comfortable ventilation should provide favorable sanitary hygiene conditions for people working in these premises.

The required meteorological conditions in the premises must be ensured in the working area of ​​the premises or at workplaces. The working area of ​​the premises is taken as a space with a height of 2 m from the floor level or the platform on which it is located. workplace. Design parameters air - temperature, relative humidity and air mobility - for various workshops and industrial premises, depending on the category of human work and the conditions of the technological process.

The task of ventilation of premises is to maintain in them a state of the air environment favorable for a person in accordance with its normalized characteristics.

The chemical composition of indoor air depends on the length of time people stay in them, the operation of technological gas-emitting equipment. The maximum permissible content (concentration) of various harmful gases and vapors (MAC) established by research is given in GOST 12.1 005 76.

Depending on the chosen method, which determines the principle of operation of systems and their design, ventilation is distinguished: general exchange, local and localized.

At general ventilation there is a dilution of hazards in the entire volume of the room due to the influx fresh air, which, passing through the room, assimilates the released harmful substances and then is thrown out.

Quantity supplied ventilation air(air exchange) is calculated to dilute the emitted hazards to the concentrations allowed at the workplace.

The main indicator for choosing this method is the location of people's locations and possible sources of harmful emissions throughout or over a large area of ​​the premises. The disadvantage of this method is the unequal sanitary and hygienic conditions of the air environment in different places premises, as well as the possibility of their unacceptable deterioration near sources of harmful emissions or places of air exhaust from the premises.

The latter must be taken into account and, if possible, eliminated by the appropriate location and purpose of the required number of devices for distributing and extracting ventilation air.

General ventilation is provided in residential and public buildings. In rooms where the release of heat and moisture causes a natural rise in air, the hood is usually carried out from the upper zone. ventilation fire hazard material radiation

It is advisable to supply the supply air in such a way that it reaches people as clean and fresh as possible, without disturbing comfortable conditions.

Classification ventilation systems by appointment

Ventilation systems can be divided into supply and exhaust according to their purpose. Supply systems are used to supply clean air to ventilated rooms instead of contaminated air. In this case, if necessary, the supply air can be processed, for example, cleaning, heating and humidification.

System supply ventilation consists of an air inlet, a supply chamber, a network of air ducts and devices for supplying air to the room.

Rice.

• 1. Fence device.
• 2. Cleaning device.
• 3. Air duct system.
• 4. Fan.
• 5. The device of giving on the worker. place.

Local supply ventilation devices include air showers, air curtains and air heating.

An air shower is a device in the local supply ventilation system that provides a concentrated air flow. The supplied air creates in the zone of direct impact of this flow on a person the conditions of the air environment that meet hygienic requirements.

Air and air-thermal curtains are arranged in order to cold air V winter time didn't get through open doors V public buildings through open doors to public buildings and through gates to industrial facilities. air curtain- this is a flat jet of air, which is supplied from the sides of the gate or door at a certain angle towards the outside cold air. For air-thermal curtains, the air supplied by the fan is additionally heated.

In systems air heating air is heated in heaters to certain temperature and then fed into the room. In heaters, the air is heated by hot or superheated water, steam or hot gases.

Exhaust ventilation serves to remove polluted or heated exhaust air from the room. To exhaust ventilation systems industrial ventilation include aspiration or pneumatic conveying systems bulk materials, as well as production waste - dust, shavings, sawdust, etc. These materials are moved through pipes and channels by air flow.

Rice.

• 1. Air removal device.
• 2. Fan.
• 3. Air duct system.
• 4. Dust and gas trapping devices.
• 5. Filters.
• 6. Air ejection device.

In aspiration systems, special fans, cleaning devices, dust collectors and other equipment are used. Aspiration systems are widely used in woodworking enterprises to remove chips and sawdust from machine tools, in elevators for loading grain into vehicles, in cement plants when loading cement, in foundries for transporting sand and burnt earth.

In the general case, both supply and exhaust systems are provided in the room. Their performance must be balanced with regard to the possibility of air entering adjacent rooms or from adjacent rooms. In the premises, only an exhaust or only a supply system can also be provided. In this case, the air enters the room from the outside or from adjacent rooms through special openings, or is removed from the room to the outside, or flows into adjacent rooms.

An effective means of ensuring proper cleanliness and allowed parameters air microclimate working area is industrial ventilation. Ventilation is called organized and regulated air exchange, which ensures the removal of polluted air from the room and the supply of fresh air in its place.

According to the method of air movement, natural and mechanical ventilation systems are distinguished. The ventilation system, the movement of air masses in which is carried out due to the resulting pressure difference outside and inside the building, is called natural ventilation. The pressure difference is due to the density difference between the external and internal air (gravitational pressure, or thermal pressure? Rt) and the wind pressure? Rv acting on the building. Estimated thermal head (Pa)

DPT \u003d gh (rn - rv),

where g is free fall acceleration, m/s2; h is the vertical distance between the centers of the supply and exhaust openings, m; рнi р^ – density of external and internal air, kg/m.

When the wind acts on the surfaces of the building on the leeward side, excess pressure is formed, on the leeward side - a vacuum. The distribution of pressures on the surface of buildings and their magnitude depend on the direction and strength of the wind, as well as on the relative position of the buildings. Wind pressure (Pa)

DРв = kп rн,

where kn„ is the aerodynamic drag coefficient of the building; the value of kn does not depend on the wind flow, is determined empirically and remains constant for geometrically similar buildings; WВ – wind flow speed, m/s.

unorganized natural ventilation-infiltration, or natural ventilation - is carried out by changing the air in the premises through leaks in the fences and elements building structures due to the difference in pressure outside and inside the room. Such air exchange depends on random factors - the strength and direction of the wind, the air temperature inside and outside the building, the type of fences and the quality construction works. Infiltration can be significant for residential buildings and reach 0.5 ... 0.75 room volume per hour, and for industrial enterprises up to 1...1.5 h-1.

For constant air exchange, required by the conditions of maintaining the purity of the air in the room, organized ventilation is necessary. Organized natural ventilation can be exhaust without an organized air supply (duct) and supply and exhaust with an organized air supply (duct and ductless aeration). Channel natural exhaust ventilation without an organized air supply is widely used in residential and administrative buildings. The design gravitational pressure of such ventilation systems is determined at an outside air temperature of +5 °C, assuming that all pressure drops in the exhaust duct path, while the resistance to air entry into the building is not taken into account. When calculating the network of air ducts, first of all, an approximate selection of their sections is made based on the allowable air velocities in the channels top floor 0.5...0.8 m/s, in channels ground floor and prefabricated channels of the upper floor 1.0 m/s and in the exhaust shaft 1...1.5 m/s.

To increase the available pressure in natural ventilation systems, deflector nozzles are installed at the mouth of the exhaust shafts. The thrust is increased due to the rarefaction that occurs when the flow around the TsAGI deflector. The vacuum created by the deflector and the amount of air removed depend on the wind speed and can be determined using nomograms.

Aeration is called organized natural general ventilation of premises as a result of the intake and removal of air through the opening transoms of windows and lanterns. The air exchange in the room is regulated by varying degrees of opening of the transoms (depending on the outdoor temperature, wind speed and direction). As a method of ventilation, aeration has found wide application in industrial buildings, characterized by technological processes with large heat releases (rolling shops, foundries, forgings). The intake of outside air into the workshop cold period years are organized so that cold air does not enter the working area. To do this, outside air is supplied to the room through openings located at least 4.5 m from the floor; in the warm season, the inflow of outside air is oriented through the lower tier of window openings (A = 1.5 ... 2 m).

When calculating aeration, determine the required flow area of ​​openings and aeration lamps for supply and removal required amount air. The initial data are the structural dimensions of the premises, openings and lanterns, the value of heat production in the room, the parameters of the outside air. According to SNiP 2.04.05–91, the calculation is recommended to be performed on the effect of gravitational pressure. Wind pressure should be taken into account only when deciding on the protection of ventilation openings from blowing.

The main advantage of aeration is the ability to carry out large air exchanges at no cost. mechanical energy. The disadvantages of aeration include the fact that during the warm period of the year, the efficiency of aeration can significantly decrease due to an increase in the temperature of the outside air, and, in addition, the air entering the room is not cleaned or cooled.

Ventilation by means of which air is supplied to or removed from production premises through systems ventilation ducts using special mechanical stimuli for this is called mechanical ventilation.

mechanical ventilation Compared to the natural one, it has a number of advantages: a large radius of action due to the significant pressure created by the fan; the ability to change or maintain the necessary air exchange, regardless of the outdoor temperature and wind speed; subject the air introduced into the room to preliminary purification, drying or humidification, heating or cooling; organize optimal air distribution with air supply directly to workplaces; capture harmful emissions directly at the places of their formation and prevent their spread throughout the room, as well as the ability to purify polluted air before releasing it into the atmosphere. The disadvantages of mechanical ventilation include the significant cost of construction and operation of it and the need for measures to combat noise.

General ventilation is designed to assimilate excess heat, moisture and harmful substances throughout the working area of ​​the premises. It is used in the event that harmful emissions enter directly into the air of the room, jobs are not fixed, but are located throughout the room. Usually, the volume of air Lpr supplied to the room during general ventilation is equal to the volume of air Lb removed from the room. However, in some cases it becomes necessary to violate this equality. So, in especially clean shops of electrovacuum production, for which great importance has the absence of dust, the volume of air inflow is greater than the volume of the exhaust, due to which some excess pressure is created in the production room, which eliminates the ingress of dust from neighboring rooms. In general, the difference between the volumes of supply and exhaust air should not exceed 10...15%.

A significant influence on the parameters of the air environment in the working area is exerted by proper organization and arrangement of supply and exhaust systems.

Air exchange created in the room ventilation devices, is accompanied by the circulation of air masses several times greater than the volume of supplied or removed air. The resulting circulation is the main reason for the spread and mixing of harmful emissions and the creation of air zones of different concentration and temperature in the room. So, the supply jet, entering the room, involves the movement of the surrounding air masses, as a result of which the mass of the jet in the direction of movement will increase, and the speed will decrease. When flowing from a round hole at a distance of 15 diameters from the mouth, the jet velocity will be 20% of the initial velocity Vo, and the volume of moving air will increase by 4.6 times.

The damping rate of air movement depends on the diameter of the outlet do: the larger do, the slower the damping. If you need to quickly extinguish the speed of the supply jets, the supply air must be divided into big number small jets.

The temperature of the supply air has a significant effect on the trajectory of the jet: if the temperature of the supply jet is higher than the temperature of the room air, then the axis bends upwards, if lower, then downwards with isothermal flow, it coincides with the axis of the supply opening.

Air flows to the suction opening (exhaust ventilation) from all sides, as a result of which the speed drop is very intense. Thus, the suction rate at a distance of one diameter from the hole round pipe equals 5% Vo.

Air circulation in the room and, accordingly, the concentration of impurities and the distribution of microclimate parameters depends not only on the presence of supply and exhaust jets, but also on their relative position. There are four main schemes for organizing air exchange during general ventilation: top-up; top - up; down up; bottom - down. In addition to these schemes, combined ones are used. The most uniform air distribution is achieved when the inflow is uniform across the width of the room, and the exhaust is concentrated.

When organizing air exchange in rooms, it is necessary to take into account and physical properties harmful vapors and gases and, first of all, their density. If the density of gases is lower than the density of air, then the removal of polluted air occurs in the upper zone, and the fresh air is supplied directly to the working zone. When gases with a density of greater air density are released, 60 ..70% of the polluted air is removed from the lower part of the room and 30...40% of the polluted air is removed from the upper part. In rooms with significant moisture emissions, the hood humid air is carried out in the upper zone, and the supply of fresh in the amount of 60% to the working zone and 40% to the upper zone.

According to the method of supply and removal of air, four schemes of general ventilation are distinguished: supply, exhaust, supply and exhaust and systems with recirculation. Through the supply system, air is supplied to the room - after it has been prepared in the supply chamber. In this case, excess pressure is created in the room, due to which air escapes outside through windows, doors or into other rooms. The supply system is used to ventilate rooms where polluted air from neighboring rooms or cold air from outside is undesirable.

Supply ventilation installations usually consist of the following elements: an air intake device 1 for intake of clean air; air ducts 2, through which air is supplied to the room, filters 3 for cleaning the air from dust, heaters 4, in which cold outside air is heated; movement stimulator 5, humidifier-drier 6, supply openings or nozzles 7 through which air is distributed throughout the room. The air from the room is removed through leaks in the building envelope.

The exhaust system is designed to remove air from the room. At the same time, a reduced pressure is created in it and the air from neighboring rooms or outside air enters this room. It is advisable to use an exhaust system if the harmful emissions of a given room should not spread to neighboring ones, for example, for hazardous workshops, chemical and biological laboratories.

Settings exhaust ventilation consist of exhaust holes or nozzles 8 through which air is removed from the room; movement stimulus 5; air ducts 2, devices for cleaning air from dust or gases 9, installed to protect the atmosphere, and an air exhaust device 10, which is located 1 ... 1.5 m above the roof ridge. Fresh air enters the production room through leaks in the building envelope, which is a disadvantage of this ventilation system, since an unorganized influx of cold air (drafts) can cause colds.

Supply and exhaust ventilation is the most common system in which air is supplied to the room by the supply system, and the exhaust system is removed; systems work simultaneously.

In some cases, to reduce operating costs for air heating, ventilation systems with partial recirculation are used. In them, the air sucked from the room is mixed with the air coming from outside. exhaust system. The amount of fresh and secondary air is regulated by valves 11 and 12. The fresh portion of air in such systems is usually 20 ... 10% of the total amount of air supplied. The ventilation system with recirculation may be used only for those rooms where there are no emissions of harmful substances or the emitted substances belong to the 4th hazard class and their concentration in the air supplied to the room does not exceed 30% of the MPC. The use of recirculation is not allowed even if the indoor air contains pathogenic bacteria, viruses or there are pronounced unpleasant odors.

Individual installations of general mechanical ventilation may not include all of the above elements. For example, supply systems are not always equipped with filters and devices for changing air humidity, and sometimes supply and exhaust units may not have a duct network.

The calculation of the required air exchange during general ventilation is carried out based on the production conditions and the presence of excess heat, moisture and harmful substances. For a qualitative assessment of the efficiency of air exchange, the concept of the air exchange rate kv is used - the ratio of the volume of air entering the room per unit time L (m3 / h) to the volume of the ventilated room Vn (m3). When correct organized ventilation the air exchange rate must be significantly greater than unity.

In a normal microclimate and the absence of harmful emissions, the amount of air during general ventilation is taken depending on the volume of the room per worker. Absence of harmful emissions is their amount in the process equipment, with the simultaneous release of which the concentration of harmful substances in the air of the room will not exceed the maximum allowable. IN industrial premises with the volume of air for each working Vni<20 м3 расход воздуха на одного работающего Li должен быть не менее 30 м /ч. В помещении с Vпi ==20...40 м3 L пi - 20 м3/4. В помещениях с Vni>40 m3 and in the presence of natural ventilation, air exchange is not calculated. In the absence of natural ventilation (sealed cabins), the air consumption per worker must be at least 60 m3/h.

Required air exchange for the entire production room as a whole

where n is the number of employees in this room.

When determining the required air exchange to combat heat surpluses, the balance of the sensible heat of the room is made up:

DQred + Gprcrtpr + Gvcrtuh = 0,

Where? Qsurplus – sensible heat excess of the whole room, kW; GprСрtpr and GBCptyx are the heat content of supply and exhaust air, kW; Ср is the specific heat capacity of air, kJ/(kg °С); tnp and tux are the temperature of supply and exhaust air, °C.

IN summer time all the heat that enters the room is the sum of heat surpluses. During the cold period of the year, part of the heat generation in the room is spent to compensate for heat loss.

The outside air temperature in the warm period of the year is assumed to be equal to the average temperature of the hottest month at 1 pm. The calculated temperatures for the warm and cold periods of the year are given in SNiP 2.04.05–91. The temperature of the air removed from the room

When determining the necessary air exchange to combat harmful vapors and gases, an equation is drawn up for the material balance of harmful emissions in the room during the time d? (With).

With equal masses of supply and exhaust air and, assuming that due to ventilation harmful substances do not accumulate in the production room, i.е. dc/d? = 0 and Sv = Spdk, we get L=GBP/(Cspdk-Spd). The concentration of harmful substances in the exhaust air is equal to their concentration in the air of the room and should not exceed the MPC. The concentration of harmful substances in supply air should be as low as possible and not exceed 30% of MPC.

With the simultaneous release into the working area of ​​harmful substances that do not have a unidirectional effect on the human body, for example, heat and moisture, the necessary air exchange is taken according to the largest mass of air obtained in the calculations for each type of production emissions.

With the simultaneous release into the air of the working area of ​​​​several harmful substances of unidirectional action (sulfur trioxide and sulfur dioxide; nitrogen oxide together with carbon monoxide, etc., see CH 245–71), general ventilation should be calculated by summing the air volumes necessary to dilute each substance separately to its conditional maximum permissible concentrations, taking into account air pollution by other substances. These concentrations are less than the normative Cpdk and are determined from the equation?ni=1

With the help of local ventilation, the necessary meteorological parameters are created at individual workplaces. For example, capturing harmful substances directly at the source of occurrence, ventilation of observation booths, etc. Localized exhaust ventilation is the most widely used. The main method of combating harmful secretions is to arrange and organize suction from shelters.

The designs of local suctions can be completely closed, semi-open or open. Closed suctions are the most effective. These include casings, chambers, hermetically or tightly covering technological equipment. If it is impossible to arrange such shelters, then partially covered or open exhausts are used: exhaust hoods, suction panels, fume hoods, side suctions, etc.

One of the most simple species local suction - exhaust hood. It serves to trap harmful substances that have a lower density than the surrounding air. Umbrellas are installed over the baths for various purposes, electrical and induction furnaces and above the holes for the release of metal and slag from the cupolas. Umbrellas are made open on all sides and partially open: on one, two and three sides. Efficiency exhaust hood depends on the size, height of the suspension and the angle of its opening. How more sizes and the lower the umbrella is installed above the site of release of substances, the more effective it is. The most uniform suction is achieved when the opening angle of the umbrella is less than 60°.

Suction panels are used to remove harmful emissions carried by convective currents in such manual operations as electric welding, soldering, gas welding, metal cutting, etc. Fume hoods- the most effective device compared to other suction devices, since they almost completely cover the source of the release of harmful substances. Only service openings remain open in the cabinets, through which air from the room enters the cabinet. The shape of the opening is chosen depending on the nature of the technological operations.

The required air exchange in local exhaust ventilation devices is calculated based on the condition of localization of impurities emitted from the source of formation. The required hourly volume of sucked air is determined as the product of the area of ​​the suction intake openings F(m2) and the air velocity in them. The air velocity in the suction opening v (m/s) depends on the hazard class of the substance and the type of local ventilation air inlet (v = 0.5...5 m/s).

The mixed ventilation system is a combination of elements of local and general ventilation. local system removes harmful substances from casings and shelters of machines. However, part of the harmful substances through the leaky shelters penetrates into the room. This part is removed by general ventilation.

Emergency ventilation is provided in those industrial premises in which a sudden entry into the air is possible. a large number harmful or explosive substances. The performance of emergency ventilation is determined in accordance with the requirements normative documents in the technological part of the project. If such documents are not available, then the performance of emergency ventilation is taken such that, together with the main ventilation, it provides at least eight air exchanges per 1 hour in the room. . The release of air from emergency systems should be carried out taking into account the possibility of maximum dispersion of harmful and explosive substances in the atmosphere.

To create optimal meteorological conditions in industrial premises, the most advanced type of industrial ventilation is used - air conditioning. Air conditioning is its automatic processing in order to maintain predetermined meteorological conditions in industrial premises, regardless of changes in external conditions and modes inside the premises. During air conditioning, the air temperature, its relative humidity and the rate of supply to the room are automatically regulated depending on the time of year, outdoor meteorological conditions and the nature of the technological process in the room. Such strictly defined air parameters are created in special installations called air conditioners. In some cases, in addition to providing sanitary norms air microclimate in air conditioners, special treatment is carried out: ionization, deodorization, ozonation, etc.

Air conditioners can be local (for maintenance individual rooms) and central (to serve several separate rooms). outside air is cleaned of dust in filter 2 and enters chamber I, where it mixes with the air from the room (during recirculation). After passing through the stage of preliminary temperature treatment 4, the air enters chamber II, where it undergoes a special treatment (washing the air with water, providing the specified parameters of relative humidity, and air purification), and into chamber III (temperature treatment). During heat treatment in winter, the air is heated partly due to the temperature of the water entering the nozzles 5, and partly, passing through the heaters 4 and 7. In summer, the air is cooled partly by supplying cooled (artesian) water to chamber II, and mainly as a result of the operation of special refrigeration machines .

Air conditioning plays a significant role not only in terms of life safety, but also in many technological processes, at which fluctuations in temperature and air humidity are not allowed (especially in radio electronics). Therefore, air conditioning units last years are increasingly being used in industrial enterprises.

KF MSTU im. N.E. Bauman

Practical lesson in the discipline "BJD"

Lesson topic:

"Methods of organizing ventilation and

conditioning to create

favorable microclimatic

working conditions,

determination of the required performance"

Time: 2 hours.

Department of FN2-KF

Providing comfortable living conditions.

1. Industrial ventilation and air conditioning.

An effective means of ensuring proper cleanliness and acceptable parameters of the microclimate of the air in the working area is industrial ventilation.

Ventilation is called organized and regulated air exchange, which ensures the removal of dirty air from the room and the supply of fresh air in its place.

Systems are classified according to the way air is moved. natural and mechanical ventilation.

The ventilation system, the movement of air masses in which is carried out due to the resulting pressure difference outside and inside the building, is called natural ventilation.

Ventilation, by which air is supplied to or removed from industrial premises through ventilation duct systems using special mechanical stimulators for this, is called mechanical ventilation.

Mechanical ventilation has a number of advantages over natural ventilation:

large radius of action due to the significant pressure created by the fan;

the ability to change or maintain the necessary air exchange, regardless of the outdoor temperature and wind speed;

subject the air introduced into the room to preliminary purification, drying or humidification, heating or cooling;

organize optimal air distribution with air supply directly to workplaces;

catch harmful emissions directly at the places of their formation and prevent their spread throughout the room;

purify polluted air before releasing it into the atmosphere.

Disadvantages of mechanical ventilation the significant cost of construction and operation of it and the need for measures to combat noise should be attributed.

Mechanical ventilation systems are subdivided for general exchange, local, mixed, emergency and air conditioning systems.

General ventilation designed to assimilate excess heat, moisture and harmful substances in the entire volume of the working area of ​​the premises.

It is used in the event that harmful emissions enter directly into the air of the room, jobs are not fixed, but are located throughout the room.

According to the method of supply and removal of air, they distinguish four schemes of general ventilation :

supply;

exhaust;

supply and exhaust;

recirculation system.

The calculation of the required air exchange during general ventilation is carried out based on the production conditions and the presence of excess heat, moisture and harmful substances.

For a qualitative assessment of the efficiency of air exchange, the concept of the multiplicity of air exchange is used K V- the ratio of the amount of air entering the room per unit of time L(m 3 / h), to the volume of the ventilated room V P(m 3). With properly organized ventilation, the air exchange rate should be significantly greater than one:

, Where K V >> 1 (1.1)

In a normal microclimate and the absence of harmful emissions, the amount of air during general ventilation is taken depending on the volume of the room per worker.

The absence of harmful emissions is the amount of them in the process equipment, with the simultaneous release of which the concentration of harmful substances in the air of the room will not exceed the maximum allowable.

In industrial premises with air volume per worker (V p1):

V p1< 20 м 3 расход воздуха на 1 работающего (L 1)

L 1 ≥30 m 3 /h

L 1 ≥ 20 m 3 / h

V p1 > 40 m 3 and in the presence of natural ventilation, air exchange is not calculated. In the absence of natural ventilation (sealed cabins), the air consumption per worker must be at least 60 m 3 / h

Mixed ventilation system is a combination of local and general ventilation. The local system removes harmful substances from the casings and shelters of machines. However, part of the harmful substances through the leaky shelters penetrate into the room. This part is removed by general ventilation.

Emergency ventilation It is provided in those industrial premises in which a sudden release into the air of a large amount of harmful or explosive substances is possible. The performance of emergency ventilation is taken such that, together with the main ventilation, it provides at least eight air exchanges in the room in 1 hour. The emergency ventilation system should turn on automatically when the MPC for harmful emissions is reached or when one of the general or local ventilation systems is stopped. The release of air from emergency systems should be carried out taking into account the possibility of maximum dispersion of harmful and explosive substances in the atmosphere.

An effective means of ensuring proper cleanliness and acceptable parameters of the microclimate of the air in the working area is industrial ventilation.

ventilationcalled organized and regulated air exchange, which ensures the removal of polluted air from the room and the supply of fresh air in its place.

Systems are classified according to the way air is moved. natural And mechanical ventilation(Fig. 3).

Ventilation

natural ventilation

mechanical ventilation

unorganized natural ventilation

general ventilation

local ventilation

organized natural ventilation

exhaust