§ 4. Sanitary standards for ventilation design and methods for determining air exchange
In accordance with sanitary standards, all production and auxiliary premises must be ventilated. IN production premises with an air volume per worker of less than 20 m 3, ventilation must be provided to ensure the supply of outside air in an amount of at least 30 m 3 / h for each worker, and in rooms with a volume per worker of more than 20 m 3 - at least 20 m 3 /h for each worker.
In industrial premises without lights and without windows, the supply of outside air per worker must be at least 60 m 3 /h. In this case, the standards of meteorological conditions must be observed, and the content of harmful vapors, gases and dust in the air of the working area must not exceed the limit values according to sanitary standards.
In rooms where the air environment is contaminated with dust, harmful vapors or gases or where significant heat generation is observed, the amount of air required to ensure the required parameters air environment in the work area, is determined by calculation based on the condition of diluting harmful emissions to acceptable concentrations or removing excess heat.
When installing supply and exhaust ventilation in interconnected rooms, it is necessary to ensure a certain ratio between the amount of supplied and exhausted air in order to prevent the flow of air from rooms with large emissions of harmful substances or with the presence of explosive gases, vapors and dust into rooms with less emissions or into rooms without these allocations.
When installing local exhaust ventilation, the amount of air removed depends on the design of the local suction, the nature of harmful emissions, the speed and direction of their movement. In this case, they are most often guided by a certain value of the air suction speed in the local suction holes, choosing it such that the most complete capture of harmful secretions is possible.
For local suction, carried out in the form of umbrellas, shelters, cabinets and chambers, the air suction speed in open holes (openings) is taken in the amount of 0.5-0.7 m/s to remove gases and vapors that have low toxicity (alcohol vapor , ammonia, etc.), and at a rate of 1.2-1.7 m/s to remove gases and vapors of high toxicity and volatility (aromatic hydrocarbons, cyanide compounds, lead vapor, etc.). The volume of air removed L using local exhaust ventilation can be calculated using the formula L = Fv * 3600 m 3 / h,
where F is the area of the lower (open) section of the umbrella or open opening, shelter, cabinet, chamber in m;
v is the speed of movement of the intake air in this opening in m/s.
The amount of air sucked out by exhaust ventilation devices from abrasive and polishing machines is calculated using the formula L = AD m 3 / h,
where D is the diameter of the circle in mm;
A is a coefficient equal to. 1.6 for abrasive machines, 2 for polishing machines and 2.4 for oscillating sanding wheels.
The air removed by local suction, containing dust, poisonous gases and harmful vapors, must be cleaned before being released into the atmosphere. The degree of purification of emissions containing dust and harmful, unpleasantly smelling substances is established depending on their maximum permissible concentration in the air of the working area of production premises and in such a way that atmospheric air within the enterprise can be used in supply ventilation without preliminary treatment (purification). ).
Page 5 of 5
4. VENTILATION
4.1. In mass housing construction, the following apartment ventilation scheme has been adopted: exhaust air is removed directly from the zone of greatest pollution, i.e. from the kitchen and sanitary premises, through natural exhaust duct ventilation. Its replacement occurs due to outside air entering through leaks in the external fences (mainly window filling) of all rooms of the apartment and heated by the heating system. This ensures air exchange throughout its entire volume.
When apartments are occupied by families, which is what modern housing construction is aimed at, interior doors are usually open or trimmed door leaf, reducing their aerodynamic drag in the closed position. For example, the gap under the doors of the bathroom and toilet should be at least 0.02 m high.
The apartment is considered as a single air volume with the same pressure.
Air exchange is regulated based on the minimum required amount of outside air per person according to hygienic requirements (approximately 30 m 3 /h) and is referred to the floor area conditionally. An increase in the occupancy rate, as well as an increase in the height of the premises, is not associated with the indicated amount of air.
It is not recommended to remove air directly from rooms in multi-room apartments, since this disrupts the pattern of directional air movement in the apartment.
4.2. SNiP “Residential Buildings” regulates a two-fold approach to design air exchange: living rooms- 3 m 3 / h per 1 m 2 of floor; kitchens and bathrooms - from 110 to 140 m 3 / h (depending on the type of stoves). The first of these values is taken into account in the heat balance (see Section 2), the second - when calculating ventilation units. The difference in approach to rationing has no physical basis. In this regard, it is recommended: for apartments with a living area of less than 37 m2 (with electric stoves) and 47 m2 (with gas stoves) the performance of exhaust ventilation should be taken based on the norms of bathrooms and kitchens; for apartments with a living area of 37 (47) m2 or more - according to the sanitary standard for living rooms. The given areas of apartments are determined from the conditions of equality of air exchange according to the sanitary norm and the norm for kitchens and bathrooms.
4.3. The calculated air exchange (clause 4.2) should be understood as the replacement of air removed from apartments with outside air in a standard volume. When assessing the amount of air exchange in an apartment, one should not take into account the amount of air coming from other rooms ( staircase, adjacent apartments).
4.4. In accordance with clause 4.22 of SNiP 2.04.05-86, the design conditions, i.e., the worst, for natural exhaust ventilation are: outdoor air temperature +5°C, calm, indoor air temperature +18 (+20)°C, the windows are open. Under these conditions, the throughput of the ventilation units is calculated. When the outside temperature drops and there is wind, the windows are closed, after which the pressure available for the ventilation system is spent on overcoming the resistance of two elements: the window filling and the exhaust ventilation network. Thus, air exchange in an apartment is a function of the resistance to air permeation of external enclosures and weather conditions. Taking into account the change in available pressure during heating season(10-15 times) and a tendency towards a maximum reduction in the air permeability of windows (to reduce excess heat consumption during low temperatures outside air) a transition is necessary from unorganized variable infiltration (both in time for one room and for a building in height and orientation of facades relative to the wind direction) to an organized controlled influx of outside air using special devices.
The performance of exhaust ventilation during the warm season is not standardized due to the possibility of air exchange through open windows.
The consumer should be able to change the air permeability of windows, following changes in meteorological conditions and focusing on their thermal sensations; however, the known elements of standard windows (window windows, narrow sashes) do not provide a normal inflow due to the complexity of smoothly regulating their opening. Coming through them outside air creates discomfort in the working area of the premises (a feeling of blowing). These elements can be used for burst ventilation, but are not suitable as constantly operating air supply devices that provide standard air exchange in apartments.
4.5. To ensure an organized flow of outside air into the premises of residential buildings, it is recommended to use adjustable air supply devices. They must meet the following requirements:
absence of discomfort in temperature and air mobility in the living area;
tightness of the device valve in the closed position;
thermal resistance supply valve - not less than the thermal resistance of the window filling;
possibility of smooth regulation over the entire range - from fully open to fully closed position;
aesthetics.
4.6. Air supply devices as one of the possible options it is recommended to make it in the form of a horizontal slot 15 mm wide in the upper part window box with a valve on the lower suspension (Fig. 1). In this case, the flow of outside air using a valve and under the influence of a convective flow from heating device under the window it deflects to the ceiling of the room, descending into the living zone, usually at some distance from the window, with parameters close to those of the internal air. Supply unit length 200 mm less length window block (100 mm on each side). In the middle of the gap (if its length is more than 1000 mm) a spacer 40 mm wide is made.
Rice. 1. Adjustable air supply device
The valve has a 10 mm thick sealing gasket made of polyurethane foam or foam rubber and covers the gap by 15 mm on each side.
The valve is equipped with a simple shut-off and control device with remote control, providing smooth adjustment of its position and locking.
The described supply devices were tested in experimental construction in climatic regions I, II and III and received the approval of hygienists (IOCG named after A. N. Sysin).
TsNIIEP engineering equipment develops working documentation for air supply devices in relation to windows of various designs and provides scientific and technical assistance in their implementation.
4.7. The incentive for consumer regulation of air supply devices is the individual perception of air-thermal comfort within the limits of the standard heat supply. Regulation of air exchange based on internal air temperature provides the consumer with ample opportunities to maintain the desired level of air-thermal comfort depending on the specific operating mode of the apartment.
4.8. Exhaust ventilation with natural impulse is usually performed in accordance with the diagrams, Fig. 2. The circuit shown on the right is preferable. In this case, each apartment is connected to the prefabricated exhaust duct through a travel companion.
Rice. 2. Possible schemes natural duct exhaust ventilation
The ventilation network is formed from floor blocks standardized according to the height of the building.
4.9. Air is released into the atmosphere:
a) in a cold attic through exhaust shafts that complete each vertical of the ventilation units and transit through the attic space.
Application of prefabricated horizontal boxes in a cold attic is inevitably associated with an increase in the resistance of the general section of the ventilation network and, as a rule, leads to periodic disruptions in air circulation in the system;
b) in a warm attic through a common exhaust shaft, one per section of the house, located in the central part of the corresponding section of the attic. In this case, air from the ventilation ducts of all apartments enters the attic volume through the heads in the form of a diffuser.
When calculating and installing a warm attic and a prefabricated exhaust shaft, you should use the Design Recommendations reinforced concrete roofs with a warm attic for multi-storey residential buildings / TsNIIEP housing. - 1986.
It is not recommended to allocate a separate channel in the head for the upper floor, since this eliminates the ejection of air from the companions of the upper floors.
4.10. When designing ventilation units, it is recommended:
strive for a minimum number of exhaust ducts (as a rule, a prefabricated one - one, companions of a minimum length, but not less than 2 m);
ensure the stability of the geometry of individual units during the manufacturing process of ventilation blocks;
ensure that the throughput of all channels of the ventilation unit is maintained within the design tolerances for its displacement during the installation process.
The use of left- and right-handed ventilation units is undesirable due to frequent violations of the ventilation circuit during installation.
4.11. Natural exhaust ventilation of a residential building is a complex hydraulic system, the calculation of which requires a special program for mathematical modeling on a computer.
A simplified calculation can be carried out using the TsNIIEP engineering equipment methodology.
Calculation of natural exhaust ventilation is aimed at:
to determine the cross-section of channels and the geometry of their merging nodes, as well as the entrances to the channels of ventilation units, ensuring their nominal throughput;
to determine the scope of application of existing or newly developed ventilation units, depending on the number of storeys and other structural and planning solutions of buildings.
4.12. To reduce errors when performing exhaust ventilation in various buildings, it is necessary to maximize the unification of currently used and newly developed ventilation unit designs and reduce their range, which can be done on the basis of a simplified calculation of ventilation units (see 4.11).
4.13. Increasing the operational reliability (preventing “tipping over” of the air flow) of the natural exhaust ventilation system and at the same time reducing material consumption and labor costs are achieved when using one vertical exhaust ducts per apartment through the use of combined ventilation units. An example of a solution for a combined ventilation unit combined with a sanitary cabin is shown in Fig. 3.
Rice. 3. Combined ventilation unit combined with a plumbing cabin
1 - “hood” with ventilation block; 2 - the bottom of the engineering cabin; 3 - sealing gasket; 4 - wire stops, 5 - interfloor covering
The use of two combined or combined and separate ventilation units in zoned apartments leads, as a rule, to excessive intensification of air exchange and is therefore undesirable.
When using two ventilation units in the same vertical of apartments, it is necessary to ensure the same conditions for the exhaust of ventilation air into the atmosphere (in particular, the emission mark in the case of independent mines).
4.14. The use of identical ventilation units along the height of the building determines the unevenness of air removal along the vertical of the apartments.
Increasing the uniformity of air flow distribution is achieved by increasing the resistance of the entrance to the ventilation unit or ensuring that the resistance value of the entrance to the ventilation unit varies along the height of the building. The latter can be achieved using ventilation grilles with mounting adjustment (for example, the design of TsNIIEP engineering equipment) or special linings (for example, made of hardboard) with holes different sizes at the entrance to the ventilation block.
Expanding the scope of application of ventilation units for buildings of different heights and changing their nominal performance (see clause 4.2) is possible with the help of specially designed linings.
4.15. The design and installation technology of ventilation units must provide for the possibility of sealing their interfloor joints.
The tightness of the ventilation network is of particular importance for natural exhaust ventilation. The presence of leaks not only leads to excessive air exchange in apartments on the lower floors multi-storey buildings, but also to the emissions of polluted air through them from the collection channel into the apartments of the upper floors. Projects must include special technology sealing interfloor joints of ventilation blocks using elastic gaskets.
4.16. Sustainable removal of air from apartments on the upper floors is ensured by the correct selection of ventilation units for buildings of a specific number of floors and attic design.
Installation exhaust fans at the entrance to the ventilation unit of the two upper floors, provided for by SNiP, worsens the air exchange in the apartments, since the fans are not designed for permanent job, and during periods of inactivity they make it difficult to remove air due to excessive resistance.
4.17. Designs of transit sections of ventilation units passing through cold or open attics, as well as ventilation shafts on the roof must have a thermal resistance no less than the thermal resistance of the external walls of residential buildings in a given climatic region. To reduce the weight and dimensions of these structures, as provided for in this paragraph, thermal resistance can be achieved by effective thermal insulation. The same applies to the ventilation sections of sewer risers and garbage chutes.
According to regulatory documentation: SNiP and safety standards for the creation of ventilation systems, the frequency of air exchange is regulated in terms of the amount of toxic components.
Process description
For effective assessment of air exchange characteristics in a building industrial use the value used is “kV”. This air exchange rate is the ratio of the total volume of air that comes “L” (m 3 \ h) to the total volume of cleaned space in the room “Vn” (m 3). The calculation is carried out for the accepted time period.
If during design, all calculations and the project itself are organized correctly, according to standards, then the air exchange rate for industrial premises will range from 1 to 10 units.
In addition to the calculation formulas and theoretical basis, to determine the required indicator, experts advise conducting studies of natural conditions at similar operating enterprises where there is actual data on the release of toxic vapors, gases, etc.
To determine the multiplicity index, industry documents, SNiPs, and sanitary standards are used.
Air circulation in industrial buildings
When constructing and planning buildings for future industrial needs, it is necessary to correctly calculate the ventilation routes in the premises and determine the process of air circulation. To do this, you will need such a characteristic as the air exchange rate, which is determined from tabular data on the presence of toxic substances in the space: oxides, acetylene oxides, etc.
When calculating the process of air circulation in a building, the amount of heat generated is taken into account so that the resulting amount, greater than the norm, can be removed year-round, without difficulties or obstacles.
To reduce excess heat, aeration is used. This process has received widespread in the chemical industry, for example, in thermal production areas. In this case, the air exchange rate in the warm season reaches 40-60 points due to aeration.
With such indicators of air exchange, the organization of airways, meteorological standards provided for by sanitary standards are achieved.
Thus, the direct arrangement and construction of premises subsequently affects the calculated air exchange rate; for this purpose, special working openings are provided that can be opened, guaranteeing the possibility of workers receiving fresh air and removal of unfavorable elements.
Determination of the multiplicity index
When performing production and technological calculations for the main premises, the established large equipment. For example, if pumping units are installed at the main production site, without specialized exhaust ventilation, then the amount of harmful gases in the atmosphere will be 6-7 times higher than those limited by official standards.
In auxiliary, additional production premises, except for washing departments, the air exchange rate is calculated based on the exchange rate indicators.
The production must have a system emergency ventilation, which ensures prompt removal of high concentrations of harmful and toxic particles from industrial buildings. Such a system is relevant when departing from established standards production route and in emergency situations. In order to exclude the possibility of the passage of unfavorable components through the connecting paths in the building, it is recommended to organize emergency exit paths without a compensatory inflow component.
Multiplicity table
Regulatory documents for calculating air exchange
The air exchange rate of the hood communication system is formed based on industry safety data and regulated sanitation standards. The air exchange rate is set individually for a specific room, according to the calculated information in the project.
In SNiP, TB and specialized standards of each specific industry and industrial design and construction, different information is given on the frequency of air exchange (hourly). All values are given depending on the type of industrial premises:
- additional auxiliary premises;
- working shop areas.
Thus, the corresponding SNiP regulates the characteristics numeric values(calculated) for production-type auxiliary premises.
Also, the values of the air exchange rate are listed in SNiP P-92-76 for secondary buildings.
With the constant formation of an industrial zone in space toxic gases and increasing degrees, the maximum prescribed value is taken as the multiplicity norm for each type of unfavorable industrial hazardous emissions.
So, having the value of the total volume of the room (m 3) and the rate of air exchange, using simple mathematical formulas, you can calculate the required volume of incoming air for a certain zone, per hour.
L = n * S * N, Where:
L- required productivity m3/h;
n- air exchange rate;
S- room area, m2;
N- room height, m.
Air exchange standards for industrial premises
For industrial buildings, a general ventilation system is provided, the needs of which are calculated based on the conditions of a specific production and the availability of a certain quantity:
- heat;
- liquid or condensate;
- harmful particles.
If there is equipment with gas or steam emissions in the room, the amount of required air exchange is calculated taking into account the emissions:
- from this equipment;
- laid communications;
- provided fittings.
All necessary indicators are included in technical documentation premises, otherwise the data is taken from the actual parameters. This calculation is regulated by VSN21-77 and the corresponding SNiP.
If during calculations the air exchange rate exceeds ten times, it is necessary to make an adjustment to one of the construction sections of the documents. Thus, to reduce the level of industrial harmful and toxic particles, it is necessary to provide additional measures around the perimeter of the entire room.
Sanitary standards for the design of industrial enterprises
According to the rules of SNiP, allocated to industrial premises any unfavorable elements such as moisture and heat are taken into account from the calculations of the technological part of the design documentation.
If such data is not included in the technological design standards, the number of production harmful substances, allocated in the room, can be taken based on the natural collected facts of the study. Also, the required value is indicated in the passport papers of the purchased specialized equipment.
Emissions of toxic substances into space occur through concentrated and dispersed devices of the general ventilation system.
The calculation of emitted substances should include their quantity not exceeding:
- The maximum value for the city and settlements.
- Indicators of the maximum amount in the air that penetrates into residential buildings through windows using the principle of natural ventilation (30% of the established limit on the amount of concentration of harmful, toxic substances in the work area).
Determining the coefficient of dispersion into the working space of toxic elements present in the system at the time of release is part of the ventilation design of the enterprise. So, according to the standards, in industrial premises, provided the air volume per subject is 20 m 3, it is necessary to take into account the process of supplying outside air. So in total it should be up to 30 m3/h for each subject located in the premises. If there are more than 20 m3 per person, the amount of air supplied from outside should be at least 20 m3/h for each subject.
For a work area in which the air volume is more than 40 m 3, subject to the location ventilation windows and transoms and in the absence of toxic elements, the standards provide for a working (active) natural ventilation system.
When creating a project for a work area for industrial production purposes, in which there is no natural ventilation, and with the supply of outside air only through existing mechanical ventilation, the total amount of air must be at least 60 m 3 / h per subject. The indicator can vary within the tabular data, but at the same time be at least one multiple of the air exchange flow per hour.
Issues related to the requirements for the design of ventilation, air conditioning, methods of aerodynamic testing of ventilation systems, monitoring ventilation efficiency, etc., are set out in the following regulatory documents:
SNiP 41-01-2003 Design standards. Heating, ventilation, air conditioning;
GOST 12.1.005-88. SSBT. General sanitary and hygienic requirements for the air in the working area;
GOST 12.1.016-79. SSBT. Work area air. Requirements for methods for measuring the concentration of harmful substances;
GOST 12.3.018-79. SSBT. Ventilation systems. Aerodynamic test methods;
GOST 30494-96 Interstate standard. Residential and public buildings. Indoor microclimate parameters.
SanPiN 2.2.4.548-96. Hygienic requirements for the microclimate of industrial premises;
SP 2.2.1.1312-03 Hygienic requirements for the design of newly built and reconstructed industrial enterprises
Sanitary and hygienic control of ventilation systems of industrial premises. Guidelines No. 4425-98, etc.
Production and auxiliary premises must be equipped with supply and exhaust ventilation in accordance with the requirements of SNiP 41-01-2003. Natural ventilation can also be used for ventilation. The use of one or another ventilation must be justified by calculation and defined in the project.
The air in the working area must comply with the sanitary and hygienic requirements of GOST 12.1.005-88.
Air intake for the supply ventilation system should be carried out from an area where the content of radioactive and toxic substances, as well as dust, in the atmospheric air is no more than 0.1 MAC and 0.3 MAC for work premises.
The amount of air required for general ventilation of industrial premises should be calculated for each harmful factor: moisture, heat, dust, gas, as well as by the number of workers and take into account the largest value obtained in the calculation.
The air in the work area must contain at least 20% oxygen by volume and no more than 0.5% carbon dioxide.
Ventilation units installed after reconstruction or overhaul, must be tested to determine their effectiveness and reliability in operation.
For each ventilation system, a passport must be drawn up indicating the technical parameters and the procedure for its operation and maintenance must be determined.
Ventilation systems must be tested:
When assessing newly commissioned systems to determine compliance with design data;
During a routine inspection of sanitary and hygienic working conditions (at least once every three years);
When investigating cases of occupational poisoning;
At the request of state supervisors;
If there are disturbances in the normal operation of the system, etc.
During work technological equipment all main supply and exhaust ventilation units must operate continuously. If the ventilation systems are faulty, the operation of technological equipment, the operation of which is accompanied by the release of dust and gas, is prohibited.
If the ventilation unit is stopped or the concentration of harmful substances increases above sanitary standards, work in the room must be immediately suspended and people removed from the room.
Air sampling to determine temperature, humidity and air velocity in workplaces should be carried out systematically both under normal operating conditions and in cases of change technological mode after reconstruction and overhaul of ventilation units in accordance with MU No. 4425-98.
Heating
Heating involves maintaining in all industrial buildings and structures (including crane operator cabins, control panels and other isolated rooms, permanent workplaces and work areas during main and repair and auxiliary work) a temperature that meets established standards.
The heating system must compensate for heat loss through building fences, as well as ensure heating of the cold air entering and leaving the room, raw materials, materials and workpieces, as well as these materials themselves.
Heating is arranged in cases where heat loss exceeds
increase heat generation in the room. Depending on the coolant, heating systems are divided into water, steam,
air and combined.
Systems water heating the most acceptable from a sanitary and hygienic point of view and are divided into systems with water heating up to 100°C and above 100°C (superheated water).
Water is supplied to the heating system either from the enterprise’s own boiler house, or from a district or city boiler house or thermal power plant.
System steam heating Suitable for enterprises where steam is used for the technological process. Steam heating devices have high temperature, which causes dust to burn. Radiators, finned pipes and registers made of smooth pipes are used as heating devices.
In industrial premises with significant dust emissions, devices with smooth surfaces are installed, allowing them to be easily cleaned. Finned radiators are not used in such rooms, since the settled dust due to heating will burn, emitting a burning smell. Dust at high temperatures can be dangerous due to the possibility of ignition. The temperature of the coolant when heating with local heating devices should not exceed: for hot water- 150°C, water vapor - 130°C.
Air system heating, characterized by the fact that the air supplied to the room is preheated in heaters (water, steam or electric heaters).
Depending on the location and design, air heating systems can be central or local. IN central systems, which are often combined with supply ventilation systems, heated air is supplied through an air duct system.
Local An air heating system is a device in which an air heater and a fan are combined in one unit installed in a heated room.
The coolant can be obtained from a central water or steam heating system. It is possible to use electric autonomous heating.
Often used in administrative premises panel heating, which works as a result of heat transfer from building structures, in which pipes with coolant circulating in them are laid.
Air and air-heat curtains(air curtains with air heating) are provided at permanently open openings in the external walls of premises, at gates and openings in external walls without vestibules and opening more than five times or for at least 40 minutes per shift, at technological openings of heated buildings and structures under construction in areas with a design outdoor temperature for heating design of 15 degrees. C and below, as well as with appropriate justification and at higher design temperatures of outside air and for any duration of opening of gates and other openings.
Ventilation - technical means, which completes the system of measures to improve the air environment of working premises (the most important prerequisite for preventing air pollution in industrial premises is rational organization production processes: sealing and process continuity with remote control and monitoring, automation and mechanization).
Ventilation, heating and air conditioning of industrial premises and structures (including crane operator cabins, control panel rooms, etc. isolated premises) are arranged to provide at permanent workplaces and in the work area during the main and repair and auxiliary work necessary in accordance with hygienic requirements meteorological conditions, air purity at work (temperature, relative humidity and air speed, maximum permissible concentrations of harmful substances and dust). Industrial ventilation ensures the fight against excess heat and moisture by creating a general air exchange, as well as removing harmful gases, vapors, dust entering the air of working premises through the use of local, localized ventilation units (see also “SSBT. Gas-cleaning dust collection equipment.” GOST 4.125 -84; “SSBT.Blowout prevention equipment”.
During the sanitary examination of ventilation projects, the expert conclusion reflects the following main issues:
1) characteristics of the system and the correctness of its choice; 2) assessment of the supply system: a) place and method of intake of supply air and devices for its cleaning, heating and humidification, b) location and arrangement of supply openings in the premises, temperature and supply speed of supply air, c) assessment of the sufficiency of air exchange according to the supply (test calculation), d) cubic capacity of the room per person, air cube and exchange rate, e) recirculation, its admissibility and scale; 3) assessment of local air supply units: direction of air shower inflow, supply air temperature, air supply speed; 4) assessment of the exhaust ventilation system: a) design and location of general exhaust ventilation openings, b) arrangement of localizing shelters, c) initial speed of air movement in the openings, d) device for cleaning the air removed from the room, e) assessment of the location of the exhaust air release, f) air exchange through the hood (test calculation);
5) characteristics and assessment of the ventilation system as a whole: the ratio of the places of intake of supply air and the places of exhaust air, the ratio of the location of supply and exhaust openings in the room, the air balance of the room (i.e. the ratio total number supply and exhaust air). For a detailed description of the requirements, see “Sanitary standards for the design of industrial enterprises” (SN 245-71) and the section “Heating, ventilation and air conditioning” (SNiP 11-33-75), industry design guidelines (issued by individual departments with mandatory approval from Main Sanitary and Epidemiological Directorate of the USSR Ministry of Health).
In the absence of industrial emissions, air exchange must be organized in rooms with a cubic capacity of less than 40 m3 per worker.
The amount of air required to ensure the required air parameters in the working area is determined engineering calculation. At the same time, the uneven distribution of harmful substances, heat and moisture along the height of the room and in the working area is taken into account, namely for rooms with heat emissions - according to excess sensible heat; for rooms with heat and moisture releases - based on excess sensible heat, moisture and latent heat, checking to prevent moisture condensation on the surfaces of building structures and equipment. In those rooms where there are gas emissions, the amount of air that needs to be supplied to the room should provide dilution chemical substances up to the maximum permissible concentration. The amount of harmful emissions is taken either according to the technological part of the project or technological design standards, or according to data from natural surveys of similar enterprises, or by calculations. If there are simultaneously several harmful substances, heat, and moisture in the room, the amount of supply air when designing ventilation is taken to be the largest, obtained from calculations for each type of industrial emissions.
Emissions cleaning. Technological emissions and emissions of air removed by local suction, containing dust, poisonous gases and vapors, and unpleasant-smelling substances, must be arranged in such a way as to ensure the dispersion of these substances and so that their concentration does not exceed:
a) in the atmospheric air of populated areas - maximum permissible one-time values; b) in the air entering buildings through openings of ventilation and air conditioning systems and through openings for natural supply ventilation - 30% of the maximum permissible concentration of harmful substances in the working area of industrial premises.
Ventilation air removed by general ventilation and containing the above-mentioned impurities must be purified before being released into the atmosphere, taking into account that in places of air intake by ventilation and air conditioning systems, the content of harmful substances in the outside air does not exceed 30% of the maximum permissible concentration for the working area of production premises. If ventilation emissions contain low concentrations of harmful substances, then cleaning may not be carried out, but the dispersion of harmful substances in the atmospheric air under the most unfavorable conditions weather conditions must meet the above requirements.
Forced ventilation. Recycle. In production premises with a volume per worker of less than 20 m3, a supply of outside air in an amount of at least 30 m3/h per worker must be organized, and in premises with a volume per worker of more than 20 m3 - at least 20 m3/h per worker. every worker. If there is more than 40 m3 of room volume per worker in the presence of windows and lanterns and in the absence of the release of harmful and unpleasantly smelling substances, it is allowed to provide periodic natural ventilation - opening the casements of windows and lanterns. When designing buildings, premises and their separate zones(areas) without natural ventilation (airing) with the supply of mechanical ventilation only from outside air; the volume of outside air should be at least 60 m3/h per 1 worker, but not less than one air exchange per hour throughout the entire volume of the room (for air conditioning with recirculation - with a calculated air exchange rate of 10 times or more). With a lower design air exchange rate and when recirculation is used, the volume of outside air supply should be at least 60 m3/h per 1 worker, but not less than 20% of the total air exchange (the volume of outside air supply is up to 10% if the air exchange rate is less than 10 and recirculation - if more 120 m3/h of outside air per 1 worker.
When designing general supply and exhaust ventilation of premises without natural ventilation, at least two supply and two exhaust units must be provided, each with a capacity of at least 50% of the required air exchange (with one installation - backup fans).
When designing ventilation and air heating, recirculation can be allowed during the cold and transition periods of the year (for air conditioning systems - at all times of the year). For recirculation, you can use room air where there are no harmful emissions or if the released substances belong to hazard class IV and their concentration in the room air does not exceed 30.% of the maximum permissible concentration. The use of air recirculation for ventilation, air heating and air conditioning is prohibited in rooms in which:
a) the air contains microorganisms;
b) there are pronounced unpleasant odors; c) substances of hazard classes I, II and III are released in the air.
Air and air-heat curtains must be installed at gates that open at least 5 times per shift or at least 40 minutes per shift. These curtains are also installed at technological openings of heated buildings and structures in areas with a design outside air temperature for heating design of 15 °C or lower in the absence of airlock vestibules. When opening gates, doors and technological openings, the air temperature at permanent workplaces when operating curtains should not be lower than: 14 °C for light physical work, 12 °C for moderately heavy work, 8 °C for heavy work (in the absence of permanent workplaces near gates and openings - up to 5 °C).
The temperature of the air mixture passing through the gate or openings must meet the specified standards.
Exhaust ventilation. Merging into a common exhaust unit Suction of dust and easily condensable vapors, as well as substances that, when mixed, produce harmful mixtures or chemical compounds, is prohibited. Local exhaust systems for removing harmful substances of hazard classes 1 and 11 must be interlocked with process equipment so that it cannot operate when local exhaust ventilation is inactive (with the exception of installing backup fans for local exhaust units with automatic switching). When installing local exhaust ventilation, it is necessary to observe the following requirements: 1) sources of harmful emissions must be covered as much as possible; 2) the design of the suction air intake and its location - take into account the natural movement of emissions (convection air flows, the direction of the dust stream, the direction of gas movement, etc.); 3) the breathing zone of workers - to be outside the shelter; 4) the flow of the technological process and the ease of servicing the equipment - not to be disturbed; 5) in the shelter, by suctioning air, a vacuum must be created to prevent the entry of harmful emissions into the air of the room.
General ventilation. To dilute to the maximum permissible concentration that part of the production emissions that cannot be removed using local exhaust ventilation, general mechanical ventilation is installed. The location of the air exhaust zone depends on the nature of the harmful emissions. In the presence of heat emissions or light gases and vapors, the joint release of heat and chemicals, the exhaust air is removed from the upper zone of the room; Air removal (usually partially) from the lower zone is carried out in the event of the release of heavy specific gravity gases and vapors. Air is removed from the upper and lower zones when it is simultaneously contaminated with a mixture of gases and vapors, one of which is lighter and the other is heavier than air. You draft receivers should be located in areas of the highest temperatures and the greatest air pollution.
Supply air is usually supplied to the work area in the following cases: a) during the release of heat and the joint release of heat and gases; b) when installing exhaust from an area with the highest dust concentrations above the working area (welding shops, etc.). To the upper area of the premises supply air produced in the absence of significant excess heat and local exhaust ventilation suction of dust and gases, with lower exhaust in rooms with the release of vapors of volatile solvents or dust, in rooms with excess heat when cold air is supplied. In the presence of moisture release, supply air is supplied to two zones - the upper (heated) and the lower.
Local influx is arranged to create limited zones with a favorable microclimate and low concentrations harmful impurities air (air showers, air oases).
In industries where a sudden entry into the air of the working area is possible large quantities hazardous substances (except dust), emergency (usually exhaust) ventilation should be provided in accordance with the requirements of SNiP and departmental standards. If departmental standards do not contain instructions on the air exchange of emergency ventilation, then together with the existing ventilation it must provide an air exchange of at least 8 exchanges per 1 hour in the internal volume of the room. It is recommended to provide for blocking emergency ventilation with gas analyzers that determine permissible concentrations of harmful substances. To start emergency ventilation, remote devices must be installed in accessible places and outside the room.
Ventilation, air conditioning and heating installations should not create noise above permissible values (see noise standards).
Heating. For heating buildings and structures, systems, devices and coolants must be used that do not create additional industrial hazards. The use of radiant heating with infrared gas emitters is permitted provided that combustion products are removed to the outside. In heating systems, the average temperature of the heating surface should not be higher than:
a) on the heated floor surface 26 °C (in lobbies and rooms with temporary occupancy of people 30 °C); b) on the heating surface of the ceiling at a height of 2.5-2.8 m 28 ° C; at a height of 2.9-3 m 30 ° C; at a height of 3.1-3.4 m 33 ° C;
c) on the heating surface of partitions and walls at a height of up to 1 m from the floor 35 °C, from 1 to 3.5 m 45 °C. Heating devices in rooms with significant dust emissions they should have a smooth surface, which makes them easier to clean.
Supply heating and ventilation equipment and air conditioners that serve the premises without recirculation are placed in isolated rooms.
Each enterprise must have a designated person responsible for the operation and condition of ventilation, heating, and air conditioning. All ventilation units, both newly equipped and put into operation after reconstruction or major repairs, are subject to instrumental acceptance tests to determine efficiency.
Each enterprise must establish a procedure for operating ventilation and heating in accordance with specially developed instructions and passports (for ventilation units). The instructions contain instructions on how to regulate the operation of each unit (system) in relation to the operating mode of the workshop (department) and technological equipment (during the working day, during the seasons of the year and in different time days depending on meteorological conditions); timing of cleaning air ducts, fans, dust and gas cleaning devices; timing of scheduled preventive maintenance, etc. For all ventilation units, a passport is drawn up in a certain form, in which all changes in the installation, the results of tests carried out at the request of the sanitary-epidemiological station are entered. An operation log must be kept for each ventilation system (kept by the workshop manager). In rooms where chemicals, dust and other harmful substances may be released into the air, it is necessary to systematically test the air for the content of harmful substances within the time frame determined by local sanitary inspection authorities.
Control of ventilation units. The effectiveness of ventilation is determined only on a working ventilation unit. IN air handling unit The air heaters must be in good working order, the valves and openings for air intake must be open. Check the water temperature and the addition of steam entering the heaters, the purity of the supplied air; determine the temperature and speed of air flowing out of the supply pipes into the working room.
When checking exhaust devices, special attention is paid to the tightness of the air ducts and, first of all, in the places where the pipes are connected to shelters and main air ducts. It is important to check the tightness of the connections in the flanges of the air ducts; dust and dirt are not allowed to accumulate in them; the suction openings must be open, and the devices for cleaning the air removed from the room must be in good working order. To assess the effectiveness of ventilation, the content of dust and chemicals in the air of working areas during work is determined production equipment at full capacity. Along with this, the performance (volume of supplied or removed air per 1 hour) of ventilation units is checked and its compliance with design data using either anemometers or pneumometric tubes with a draft gauge. In this case, the speed of air movement in the duct is multiplied by the area vent(in m2) and by 3600 (number of seconds); get installation performance in cubic meters air in 1 hour.
If there are grilles in the air duct opening, then to obtain the volume of air passing through the exhaust openings, the result obtained is multiplied by a factor of 0.8. To determine the volume of air passing through the supply openings with grilles, instead of the area of the air duct opening, take half the sum of the overall area of the opening and the free cross-sectional area of the grille. It is impossible to measure the speed of air movement in the air duct with an anemometer, since this changes the nature air flow(pneumometric tubes with a draft gauge are used). These studies are carried out by specially trained personnel of ventilation laboratories or SES groups or special laboratories of departments and enterprises.
