Local exhaust ventilation of industrial premises: requirements and classification

Ventilation is a technical means that completes the system of measures to improve the air environment of working premises (the most important prerequisite for the prevention of air pollution production premises is the rational organization of production processes: sealing and continuity of processes with remote control and monitoring, automation and mechanization).

Ventilation, heating and air conditioning of production premises and structures (including crane operator cabins, control panel rooms, and other similar isolated rooms) are arranged to ensure that at permanent workplaces and in the work area during basic 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". GOST 12.2.11586).

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 the general exhaust ventilation openings, b) arrangement of localizing shelters, c) initial speed of air movement in the openings, d) device for purifying the air removed from the room, e) assessment of the location of the release of the removed air, 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 supply air intake 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 of the total amount of 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 work area is determined by engineering calculations. 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 ensure the dilution of chemicals 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 atmospheric air settlements- maximum permissible maximum 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 individual zones (sections) without natural ventilation (airing) with mechanical ventilation supplied 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 according to the entire volume of the room (with 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. Application 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 during operation of the curtains should not be lower than: 14 °C at light physical work, 12 °C - for moderate 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. The combination of dust and easily condensable vapors, as well as substances that, when mixed, produce harmful mixtures or chemical compounds, into a common exhaust system 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, the following requirements must be observed: 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.). Supply air is released into the upper zone of the premises in the absence of significant excess heat and dust and gases are sucked out by local exhaust ventilation, 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 inflow is arranged to create limited zones with a favorable microclimate and low concentrations of harmful air impurities (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 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 overhaul, are subjected to instrumental acceptance tests to determine effectiveness.

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. For each ventilation system an operation log must be kept (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. The air supply unit must have air heaters in working order, 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 is determined when production equipment is operating 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 air duct is multiplied by the area of ​​the ventilation opening (in m2) and by 3600 (the number of seconds); get the installation productivity in cubic meters of air per 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 of the 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.

To organize exhaust ventilation in a private house or cottage, it is necessary to install exhaust ventilation ducts during the construction of the house.

Very often, construction organizations violate even the minimum requirements that must be observed when organizing exhaust ventilation in a house.

Below we list the requirements for exhaust ventilation ducts of private houses and cottages:

1. Each bathroom or bathroom must have its own exhaust duct.

2. The kitchen should have 2 exhaust channels: one for the kitchen umbrella (the diameter depends on the umbrella used, but not less than 125 mm), the second channel is a natural draft channel in case of gas leakage.

3. The minimum diameter of the exhaust duct is 125 mm, the minimum cross-sectional area of ​​a rectangular duct is 0.0123 m2 (this corresponds to dimensions 100x120, 110x110, 105x125, etc.)

4. You cannot combine some exhaust ducts with other exhaust ducts. In particular, you cannot combine exhaust ducts from bathrooms, even those located on different floors.

5. The boiler room must have 2 exhaust channels: one for the boiler (the diameter depends on the power of the boiler), the second channel is a natural draft channel in case of gas leakage. The diameter of the natural channel must be no less than the diameter of the exhaust channel from the boiler. That is, if a 160 mm ventilation duct is used under the boiler, then the natural draft duct must be at least 160 mm.

6. An air flow must be organized into the boiler room in a volume that ensures normal operation of the boiler burner. The required volume of combustion air is indicated in technical specifications boiler The air flow must be organized using air infiltration valves (at the rate of 1 valve per 20 kW of boiler power) or using a flow grille in the outer door or external wall. There is no air supply through the boiler room window.

7. All ventilation ducts must reach the roof of the house above the ridge. A cap (umbrella or deflector) must be provided at the top of the ventilation duct to prevent snow, rain and debris from entering the exhaust duct. The design of the head should not impede the exit of air from the house in any weather conditions. The outlet cross-section of the head must be at least twice the cross-section of the ventilation duct.

8. Exhaust ventilation ducts are laid only vertically and should not have horizontal parts, turns, offsets, etc.

9. Exhaust ducts passing through cold rooms must be additionally insulated, as the draft may deteriorate and condensation may form.

10. Exhaust ducts are best made from stainless or galvanized air ducts. It is prohibited to use plastic air ducts or sewer pipes for this purpose. Exhaust ducts made of brick must be lined with metal air ducts to improve draft.

11. Do not use a brick exhaust duct for exhaust from the boiler. This channel must be lined with a metal air duct. The joints of metal air ducts must be sealed.

12. An exhaust ventilation duct must be installed in every room of the house that does not have opening windows.

Approximate cost of the exhaust device