Types of ventilation. Types of natural and mechanical air ventilation

The presence of a ventilation system is necessary to ensure air exchange inside the building by removing excess moisture, heat, harmful substances. Its presence is one of the main conditions for life support.

If there are no any types of ventilation systems in the room, it harms human body, leads to the formation of fungi, because. Condensation will form if there is no air exchange.

We propose to understand existing types ventilation systems and how they work.

Systems are classified according to different criteria:

• submission method;
• appointment;
• air exchange method;
• constructive performance.

The type of ventilation is determined at the design stage of the building. At the same time, both economic and technical aspects as well as sanitary and hygienic conditions are taken into account.

Types of ventilation system according to the method of supply

If based on the methods of supplying and removing air from the room, 3 categories of ventilation can be distinguished:

• natural;
• mechanical;
• mixed.

If possible, in addition to the second ventilation option, partially use the first one, mixed ventilation is included in the project. residential buildings air flow occurs through the windows, and exhaust equipment is located in the kitchen and in the sanitary room. Therefore, it is important to establish good air exchange between rooms.

In some cases, at the mouth exhaust channels mount deflectors - special nozzles. They operate by using wind energy. Deflectors do a good job of removing dirty and overheated air masses from small rooms. They are also used for local extraction.

The normal operation of the ventilation driven by the pressure difference is ensured by a minimum difference between the intake point and the exhaust outlet of 3 m.

For the effective functioning of ventilation, experts recommend that when laying air ducts, do not make horizontal sections longer than 3 m. The air in them should move at a speed of no more than 1 m / s

Characteristics of mechanical type ventilation

The ventilation system, with the help of which air is supplied and removed using additional stimuli over impressive distances, is called mechanical. There are other names for this type of ventilation - forced and artificial.

It is used both to ensure technological processes in various industries, and to create comfortable conditions for a person.

An easy-to-install and operate device that extracts exhaust air from bathrooms, kitchens and bathrooms in private houses is a ventilation system with an automatic microprocessor:

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Mechanical ventilation, unlike natural ventilation, does not depend on external conditions. It is completely controlled and managed. The air supplied to the room is processed and, with a well-functioning system, all its parameters meet the standards. Emissions also enter the atmosphere already cleaned of harmful inclusions to the required extent.

Conclusions and useful video on the topic

This video is a kind of educational program about ventilation. Here the very concept of ventilation is considered in detail and all issues related to its competent design are covered:

Master class on the installation of the ventilation system:

Both business leaders and private developers must understand that the normal life of those for whom they are responsible depends on the efficiency of ventilation. Sometimes people's lives are at stake. You can not miss this moment and save on it.

Ventilation systems are provided in all modern buildings to remove polluted air. However, often such exhaust systems do not cope with air purification. This problem is especially acute when it is necessary to remove heavily polluted air from storage facilities, workplaces in factories and other large premises with sources of air pollution. It is also common to install hoods in domestic conditions, for example, in the kitchen, in the smoking room or dressing room.

Forced ventilation

Supply systems are designed to supply clean air to the premises instead of polluted. The supply air, if necessary, can be subjected to such types of treatment as cleaning, heating, humidification, etc.

The supply ventilation system consists of:

This system includes air handling units using 100% outside air supply. They are both industrial (used at industrial facilities) and domestic (ventilation of apartments).

Air handling units can be monoblock and type-setting. Type-setting systems are assembled from separate components, and the main advantage of such systems is the ability to ventilate any premises - from small apartments and offices to trading floors, supermarkets and entire buildings. But their disadvantage is the need for professional calculation and design and in large dimensions. Monoblock systems are housed in a single soundproof housing. The advantage of such a system over typesetting is a much lower noise level, which allows them to be placed in residential premises.

Supply and exhaust ventilation

Supply and exhaust ventilation is a combination of supply and exhaust systems, which allows it to combine the advantages of both systems. This system allows you to organize the most correct air exchange.

mechanical ventilation

Mechanical ventilation involves the use of fans, air heaters, dust collectors and other energy-consuming installations designed to move air over long distances. This type ventilation is used where there is insufficient natural ventilation.

Natural ventilation.

Unlike forced ventilation and air conditioning systems, the main advantage of natural ventilation is cost-effectiveness, since the system does not use energy-intensive ventilation equipment and the naturalness of the air entering the room. Equally important advantages of natural ventilation are compactness, since the system does not clutter up the area, and low cost - does not require large installation and maintenance costs.

Channel and non-duct ventilation

According to the design, ventilation systems are divided into 2 types: ducted and non-ducted.

Channel-type ventilation systems have networks of branched air ducts that allow fresh air to be supplied or polluted air to be removed in different parts the same room or in different rooms.

Channelless ventilation systems are installed on the roof directly above the ventilated room (for example, in large industrial premises) or in door and window openings. The ductless ventilation system does not have a network of branched air ducts, and therefore such ventilation does not require large electrical costs. Also, unlike a duct system (ventilation), a ductless type ventilation system is easy to install and operate.

Duct ventilation and beskonalnaya ventilation can be both mechanical and natural. The disadvantage of a natural ducted or non-ducted ventilation system is that such ventilation is not controlled - it is designed to prevent suffocation for people in the room.

local ventilation

Local, or localizing, ventilation removes harmful substances from the premises directly in the place where their greatest accumulation occurs.

local ventilation is inlet and outlet.

General ventilation

General ventilation is installed when it is necessary to remove heat, moisture, gases, dust, odors or vapors from the air of the entire room or most of it. General exchange ventilation systems are used only in cases of insignificant emission of harmful factors and their uniform distribution throughout the entire volume of the room.

General ventilation is supply and exhaust.

General supply ventilation used to remove excess heat and moisture, as well as to dilute harmful impurities in ventilated air. In addition, general exchange supply ventilation is designed to ensure the calculated sanitary and hygienic standards, designed to ensure free breathing of a person in the working area.

In case of insufficient air temperature in the room, general exchange supply ventilation is installed with a mechanical drive, which allows you to heat the air and, as a rule, clean it from dust.

When harmful emissions enter the air of the workshop, the amount of supply air must fully compensate for general and local exhaust ventilation.

General exhaust ventilation designed to remove polluted air from a ventilated room. The simplest example of general exhaust ventilation is a separate axial-type fan with an electric motor on one axis, which is located in a window or wall opening. This installation removes air only from the zone of the room closest to it, thereby carrying out only general air exchange.

Some other installations of this type have an exhaust duct. With a duct length of more than 30-40 meters and a pressure loss of more than 30-40 kg/m2, a centrifugal fan is installed. If harmful emissions in workshops or other ventilated premises are heavy gases or dust and no heat from the equipment, exhaust ducts are laid on the floor or in the form of underground channels.

Ventilation of industrial buildings, where there are heterogeneous harmful emissions (heat, moisture, gases, vapors, dust, etc.) and their entry into the room occurs in various conditions(concentrated, dispersed, at different levels, etc.) is produced with the help of both exchange and exhaust ventilation.

IN certain cases ventilation of industrial premises, along with mechanical ventilation systems, use systems with natural impulses, for example, aeration systems.

Every building must be equipped with an efficient ventilation system, because constant air exchange is as important as good system heating or quality water. Scientists have long established a connection between the development in the houses of a number of negative phenomena and improper ventilation. Thus, good indoor air exchange is necessary not only to extend the life of the building, but also to maintain our health.

Why is ventilation needed?

The main purpose of ventilation is the organized supply of fresh air to the premises and the subsequent replacement (or removal) of polluted air. Air exchange should be carried out with a certain frequency. In buildings with poor ventilation, a lot of dust, microscopic chemicals accumulate (regular use of products household chemicals). high humidity contributes to the formation of mold, and in the air there is a high concentration of fungal spores.

A person working or living in such a building may complain of burning eyes, headaches, trouble concentrating, and fatigue. High humidity in buildings and poor ventilation indoors leads to condensation and the formation of moisture droplets on ceilings and walls.

Such conditions become ideal for the development of fungi that negatively affect human health and lead to the gradual destruction of the building. Also, these factors are very often the cause of most respiratory diseases, and for people prone to allergies, they pose a serious threat to their health.

Classification of ventilation systems

Ventilation systems are classified in four main ways:

1. According to the method of creating an air flow for circulation:

• artificial ventilation;
• with natural drive.

2. By appointment:

• exhaust systems;
• supply.

3. By service area:

• general exchange systems;
• local.

4. By design:

• channelless systems;
• channel.

The main types of ventilation

There are the following main types ventilation systems:

1. Natural.
2. Mechanical.
3. Exhaust.
4. Supply.
5. Supply and exhaust.
6. Local.
7. General exchange.

natural ventilation

As you might guess, such ventilation is created naturally, without the use of ventilation units, but only through natural air exchange, wind flows and the temperature difference between the street and the room, as well as due to fluctuations in atmospheric pressure. Such types of ventilation are relatively inexpensive in cost, and most importantly, they are easy to install. However, such systems are directly dependent on climatic conditions, therefore they are not able to cope with all problems.

Mechanical

When the forced replacement of the exhaust air with a fresh stream is carried out, this is mechanical ventilation. In this case, special equipment is used that allows you to remove and supply air to the room in the required volume, regardless of changing climatic conditions.

In such systems, the air, if necessary, is subjected to various types processing (humidification, dehumidification, cooling, heating, cleaning and much more), which is almost impossible to organize in natural ventilation systems.

In practice, mixed types of ventilation are often used, which simultaneously combine mechanical and natural systems. For each specific case, the most best way ventilation in sanitary and hygienic terms, as well as that it is technically and economically rational. The mechanical system can be installed both for the entire room (general exchange), and at a specific workplace (local ventilation).

Supply

Through the supply systems, a clean air flow is supplied to the ventilated premises, which replaces the polluted one. If necessary, the supply air is subjected to special treatment (humidification, heating, cleaning, etc.).

exhaust

Such a system is designed to remove polluted air from the premises. In most cases, the premises provide for both exhaust and supply types of ventilation. It is important that their performance is balanced, taking into account the possibility of air flow from adjacent rooms or into adjacent rooms.

Also, only the supply or only the exhaust system can be installed in the premises. In this case, air enters the room from adjacent rooms or outside through special openings, or flows into adjacent rooms, or is removed from this room to the outside.

local ventilation

This is a system in which the air flow is directed to a certain place (local supply system), and polluted air is removed from the places of accumulation of harmful emissions - local exhaust (ventilation).

Local supply system

Air showers (concentrated air flow with increased speed) refer to local supply ventilation systems. Their main task is to supply clean air to permanent workplaces, reduce the air temperature in their area, and blow air to workers who are exposed to intense thermal radiation.

Air curtains (at stoves, gates, etc.) are also local ventilation systems, they change direction or create air barriers. Such a ventilation system, in contrast to the general exchange, requires lower costs. In industrial premises, when emitting harmful substances (heat, moisture, gases, etc.), it is usually used mixed scheme ventilation: local (inflow and local suction) - for and general - to eliminate harmful air in the entire volume of the room.

Local exhaust system

When hazards (dust, gas, smoke) and heat are emitted locally, for example, from a stove in a kitchen or a machine in production, a local exhaust ventilation system is used. It captures and removes harmful emissions, preventing their subsequent spread throughout the entire volume of the room.

These systems include local and onboard suction, and much more. Also, local exhaust ventilation includes air curtains - air barriers that prevent air flow from the street into a room or from one room to another.

General ventilation

Such a system is designed to ventilate the room as a whole or a significant part of it. The general exchange exhaust ventilation scheme provides for the removal of air from the entire serviced premises evenly, and the general exchange supply system supplies the air flow and distributes it throughout the volume of the premises.

Natural or mechanical system: which one to choose?

For a comfortable existence, a person needs not only heat, but also clean, fresh air. Moreover, a person needs fresh air constantly and in in large numbers. The volumetric velocity of the air flow in the room is also important. At natural system the speed is much lower than with mechanical ventilation.

But the air exchange, which is achieved through a mechanical system, is much higher than with natural ventilation.

In addition, with a mechanical system, compared to natural ventilation, they are smaller. This is due to the normalized speed of air flow in ventilation systems. According to SNiP "Heating, ventilation and air conditioning", for a mechanical system, the air velocity should be from 3 to 5 m / s, for natural ventilation - 1 m / s. In other words, in order to pass the same volume of air through the system, natural ventilation will have duct sizes 3-5 times larger.

Very often, when building buildings, there is simply no way to skip such large channels. In addition, with a natural system, the length of the air ducts cannot be large, since the pressure created by the difference in air densities is very small. In this regard, when large areas simply can not do without mechanical ventilation.

Room ventilation - the main components

The composition of heating, ventilation and air conditioning includes a mass of units that provide highly efficient circulation of air masses in the room. It is important that the ventilation project, as well as the placement of devices, be carried out in accordance with the current rules and regulations (TKP, SNiP).

Ventilation systems may or may not have ducts - it all depends on design features premises.

It is important to remember that ventilation is a serious and significant element, so both the design and selection of equipment must be approached competently. It is also worth noting that universal and a wide variety of units are used to organize controlled air exchange. Fans are considered the most affordable and simple - they can be radial, axial and diametrical.

In addition, indoors can be installed ventilation units, which are mounted in special channels - air ducts, or on the roof of buildings. It also includes a device air valves, dampers, distribution elements and gratings, which allow you to make the movement of air flow in the room as efficient as possible.

Main parameters of ventilation systems

1. Performance. When calculating this parameter, it is necessary to take into account the number household appliances, the number of people living in the house, as well as the area of ​​\u200b\u200bthe premises. It should be calculated how much time and how much volume the ventilation system will need to remove polluted air and then fill it with clean air. For cottages, the most optimal value of air exchange is considered to be from 1000 to 2000 m 3 / h. To calculate the area of ​​\u200b\u200bthe room is multiplied by its height and by 2.
2. Noise level. The higher the ventilation speed, the higher the noise level. No need to purchase too "fast" systems. If the first point is calculated correctly, then you will be able not only to save your budget, but also to have a restful sleep. In this case, the installation of ventilation will be correct. Also, do not buy air ducts with low performance, as they will be difficult to install correctly, and they will not be able to withstand the load during operation. Suitable for a cottage average speed air flow is from 13 to 15 m/s.
3. Another important parameter is power. The temperature of the air entering the room is regulated by the heater. According to SNiP "Heating, ventilation and air conditioning", the temperature should not exceed +16°C. Depending on the intended installation location of the device, the power of the heater is calculated. It is important that it can work even at sub-zero temperatures in winter period time. When choosing power, you should focus on the maximum plus and minus temperature indicators. If the street is maximum subzero temperature-10°C, the heater must heat the air by at least 26°C. For example, for office space up to 50 kW of power can be used, 1-5 kW is quite enough for an apartment.

scheme and installation - the main stages

Even at the design stage, it is necessary to determine the attachment points for ventilation equipment, both main and auxiliary. In this case, there are some restrictions - it is not recommended to install the equipment above heat sources (stove, fireplace, etc.). It is important that the ventilation project fully complies with the requirements that apply to regulatory and technical documentation.

The device of the ventilation system involves the following main steps:

1. Preparation.

• The marking of the places of the proposed installation is in progress ventilation devices.
• Taking into account the margin (2-3 centimeters), holes are hollowed out. The stock is required for comfortable installation of the system.
• The edges of the holes are cleaned.

• The front part of the fan is installed in the pipeline section.
• Then the design is placed in the hole.
• The space between the fan and the wall is filled with foam.

3. Electrical installation.

• Grooves are made in the wall for the cable.
• The cable to the fan is laid in the resulting holes.
• The cable is fixed with brackets.

4. Finishing work.

• A protective box is installed on the fan switch.
• All joints of the ventilation system are smeared with sealant.
• Furrows with wiring, as well as the junction of the system to the wall, are plastered and puttied.

The system is completely ready to start. This is a simple ventilation, the price of such a system will depend on the cost of the fan.

Conclusion

Heating, ventilation and air conditioning systems are an integral part modern office, house or any other property. These systems consist of the most innovative and modern units, designed depending on the design features of the building, allowing you to save a lot on heating.

It is important to remember that a well-designed and installed ventilation system is the key to creating an optimal microclimate in the room.

Entering any room, be it an apartment, office, production, medical or educational institution, without noticing it ourselves, we determine whether the ventilation system works well. Of course, the first words will not be “how bad the ventilation works”, but “oh, what a heavy air in this room.” And when the ventilation is in good working order and works well, a person does not smell foreign odors, he feels good.

Types of ventilation: a general approach

So, ventilation is an engineering system that is designed to provide air exchange that maintains a certain temperature and humidity regime. Unlike other systems, ventilation is able to function without the use of any equipment and devices, based on physical laws. Its main purpose is to supply clean air filled with oxygen into the room and remove exhaust air saturated with carbon dioxide.

The need to maintain a certain regime in any room makes the ventilation system the most demanded of all engineering systems. Existing classification divides ventilation systems into four categories:

1. By the action of air exchange (natural, forced).
2. Mixed (supply, exhaust).
3. Zonal (general exchange, local).
4. By construction (with channels, without channels).

Ventilation and its types have their own characteristics, although they all have the same purpose - to create a favorable microclimate for comfortable living and work of a person. The question of which system will be supplied to the construction site is considered at the design stage.

In order to understand what is the purpose of ventilation of a certain type, you need to understand their features. After all, from right choice conditions depend correct operation. For a certain room, building codes have their own special regime of humidity and temperature.

Purpose of supply and exhaust ventilation: advantages and disadvantages

The most common ventilation system is with natural air movement. It perfectly copes with its functions of supplying air supplied with oxygen and removing spent masses, if nothing interferes with their movement. The principle of its operation is based on physical laws:

• the difference in temperature and pressure inside the room and outside it;
• pressure difference between room and place installed hood(usually on the roof);
• wind pressure.

Advantages supply and exhaust system are that its device does not require special equipment. The absence of ventilation devices does not provide for their maintenance, energy costs.

Disadvantages:

Firstly, the presence of factors that interfere with the correct operation of the system:

• Metal-plastic or wooden sealed windows and doors.
• The ventilation duct is clogged with debris, snow, waste products of birds, their nests.
• Freezing, therefore, reduction or complete blockage of the exhaust pipe in the cold season.
• Incorrectly arranged hood above the roof, because of which it falls into the zone of wind backwater. Therefore, the exhaust pipe must rise above the roof ridge by at least 50 cm.
• IN high-rise building- neighbors can break the ventilation box during repairs.
• Reverse thrust can be "organized" by a powerful kitchen hood, which interrupts the flow of exhaust air towards the sanitary rooms and begins to draw not only gases and vapors from the kitchen, but also from the ventilation openings.

Secondly, since the principle of operation is based on the temperature difference, the ventilation works correctly only in the cold season or at night.

Important! Such a ventilation system is installed during construction apartment buildings. Exhaust openings, in accordance with building codes, are placed in the kitchen, bathroom and toilet rooms.

Mechanical and mixed ventilation: their brief description

mechanical system

Mechanical ventilation is an improved natural one, that is, supply and exhaust processes are carried out using special equipment (fans, electric air heaters, filters, recuperators, sometimes ionizers). The disadvantages of such systems are: expensive equipment; complex installation; dependence on the voltage in the network; electricity costs.

The main advantage is correct operation at any time of the year, regardless of temperature. In addition, the air coming from the street is cleaned of harmful impurities and heated to a comfortable temperature (if there is an air heater or a heat exchanger in the system).

Combisystem

Mixed ventilation is supply and exhaust, in which one of the processes of natural flows is replaced by forced ventilation. Supply ventilation helps to improve the process of supplying fresh air into the room. For it, mechanical (window or wall) are used. supply valves) or electrical (fans, air handling units).

Exhaust fans are the extraction equipment. They are installed in the ventilation openings in the sanitary rooms, they are also mounted in the kitchen, in the wall with access to the street. Such devices significantly improve air exchange. An elementary hood for a private house consists of: a valve; fan; exhaust shaft; electric motor; air duct; deflector.

Important! The ventilation system with mechanical stimulation is effective for installation in private houses, where it is difficult to maintain the required microclimate on several floors. Such a system works successfully in rooms with a swimming pool.

Zonal ventilation: types

This is a fairly specific system with several areas of application. What is the peculiarity of the system types?

The local supply ventilation system delivers clean air to specific workplaces, lowers the temperature in a given area. With the help of such an inflow, air partitions are reproduced or the direction of air flows is changed.

The general exchange inflow assimilates excess heat and moisture, dilutes harmful fumes that are not removed by the zonal exhaust. If the incoming air is not warm enough, then a heater is installed. Such systems work where it is necessary to ensure circulation throughout the room or in most of it.

Local exhaust is used to remove waste and polluted air flows from certain places. It is used in production shops, entertainment centers, where it is important that carbon monoxide, dust, smoke did not get into other rooms. As equipment of the exhaust system use:

• side suctions;
• umbrellas;
• veils;
• casings;
• cabinets.

General exchange hood - an exhaust unit with a powerful fan that removes exhaust air masses from the premises where it is installed.

Important! Zone ventilation systems are installed in industries where there are harmful emissions. It is not advisable to install them in apartments or private houses.

The designs of ventilation systems differ in the presence of channels for air exchange and without it when the devices are built in (wall, window). Channelless systems mainly correct the incorrect operation of natural ventilation in apartments. The channel is installed in cottages, industrial premises, offices. Air moves through channels, consisting of air ducts and fittings.

Ventilation is a set of measures and devices used in the organization of air exchange to ensure a given state of the air environment in rooms and workplaces in accordance with SNiP (Building Codes).

Ventilation systems ensure the maintenance of acceptable meteorological parameters in rooms for various purposes.

With all the variety of ventilation systems, due to the purpose of the premises, the nature technological process, type of harmful emissions, etc., they can be classified according to the following characteristic features:

• According to the method of creating pressure to move air: with natural and artificial (mechanical) stimulation.
• By appointment: supply and exhaust.
• By service area: local and general exchange.
• By design: channel and channelless.

Natural ventilation.

The movement of air in natural ventilation systems occurs:

• due to the temperature difference between the outdoor (atmospheric) air and indoor air, the so-called aeration;
• due to the pressure difference of the "air column" between the lower level (served room) and top level - exhaust device(deflector) installed on the roof of the building;
• as a result of the so-called wind pressure.

Aeration is used in workshops with significant heat emissions, if the concentration of dust and harmful gases in the supply air does not exceed 30% of the maximum allowable in the working area. Aeration is not used if, according to the production technology, pre-treatment of the supply air is required or if the inflow of outside air causes the formation of fog or condensate.

In rooms with large excesses of heat, the air is always warmer than the outside. Heavier outdoor air, entering the building, displaces less dense warm air from it.

In this case, air circulation occurs in the enclosed space of the room, caused by a heat source, similar to that caused by a fan.

In natural ventilation systems, in which air movement is created due to the pressure difference of the air column, the minimum height difference between the level of air intake from the room and its discharge through the deflector must be at least 3 m. 3 m, and the air velocity in the air ducts must not exceed 1 m/s. The impact of wind pressure is expressed in the fact that on the windward (facing the wind) sides of the building an increased pressure is formed, and on the leeward sides, and sometimes on the roof, a reduced pressure (vacuum).

If there are openings in the building fences, then on the windward side atmospheric air enters the room, and with the leeward - leaves it, and the speed of air movement in the openings depends on the speed of the wind blowing the building, and, accordingly, on the magnitude of the resulting pressure differences.

Natural ventilation systems are simple and do not require complex expensive equipment and flow. electrical energy. However, the dependence of the efficiency of these systems on variable factors (air temperature, wind direction and speed), as well as a small available pressure, does not allow solving all complex and diverse tasks in the field of ventilation with their help.

mechanical ventilation.

In mechanical ventilation systems, equipment and devices (fans, electric motors, air heaters, dust collectors, automation, etc.) are used that allow air to be moved over considerable distances. The cost of electricity for their work can be quite large. Such systems can supply and remove air from local areas of the room in the required amount, regardless of changing ambient air conditions. If necessary, the air is subjected to various types of treatment (cleaning, heating, humidification, etc.), which is practically impossible in systems with natural motivation.

It should be noted that in practice so-called mixed ventilation is often provided, i.e., both natural and mechanical ventilation.

Each specific project determines which type of ventilation is the best in sanitary and hygienic terms, as well as economically and technically more rational.

Forced ventilation.

Supply systems are used to supply clean air to ventilated rooms instead of the removed one. supply air in necessary cases undergoes special treatment (cleaning, heating, moistening, etc.).

Exhaust ventilation.

Exhaust ventilation removes polluted or heated exhaust air from the room (workshop, building).

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, air enters the given room from the outside or from adjacent rooms through special openings, or is removed from the given room to the outside, or flows into adjacent rooms.

Both supply and exhaust ventilation can be arranged at the workplace (local) or for the entire room (general exchange).

local ventilation.

Local ventilation is one in which air is supplied to certain places (local supply ventilation) and polluted air is removed only from places where harmful emissions are formed (local exhaust ventilation).

Local supply ventilation.

Local supply ventilation includes air showers (concentrated air flow at an increased speed). They must supply clean air to permanent workplaces, reduce the ambient air temperature in their area and blow on workers exposed to intense thermal radiation.

Local supply ventilation includes air oases - areas of premises fenced off from the rest of the premises by movable partitions 2-2.5 m high, into which air with a low temperature is injected.

local supply ventilation also used in the form air curtains(at gates, stoves, etc.), which create, as it were, air partitions or change the direction of air flows. Local ventilation is less expensive than general ventilation. In industrial premises, when hazards (gases, moisture, heat, etc.) are released, a mixed ventilation system is usually used - common to eliminate hazards throughout the entire volume of the premises and local (local suction and inflow) to service workplaces.

Local exhaust ventilation.

Local exhaust ventilation is used when the places of harmful emissions in the room are localized and it is possible to prevent their spread throughout the room.

Local exhaust ventilation in industrial premises ensures the capture and removal of harmful emissions: gases, smoke, dust and heat partially released from the equipment. To remove hazards, local suctions are used (shelters in the form of cabinets, umbrellas, side suctions, curtains, shelters in the form of casings near machine tools, etc.).

The main requirements they must meet are:

• The place of formation of harmful emissions should, if possible, be completely covered.
• The design of the local suction must be such that the suction does not interfere with normal operation and did not reduce productivity.
• Harmful emissions must be removed from the place of their formation in the direction of their natural movement (hot gases and vapors must be removed upwards, cold heavy gases and dust - downwards).

The designs of local suctions are conditionally divided into three groups:

• half open blowjobs ( fume hoods, umbrellas). Air volumes are determined by calculation.
• Open type (onboard suction). Removal of harmful emissions is only achieved with large volumes of exhausted air

The main elements of such a system are local exhausts - shelters (MO), a suction duct network (VS), a fan (B) of a centrifugal or axial type, VSh - an exhaust shaft.

When installing local exhaust ventilation to trap dust emissions, the air removed from the workshop, before being released into the atmosphere, must be preliminarily cleaned of dust. The most complex exhaust systems are those in which very a high degree air purification from dust with the installation of two or even three dust collectors (filters) in series.

Local exhaust systems are usually very effective, as they allow you to remove harmful substances directly from the place of their formation or release, preventing them from spreading indoors. Due to the significant concentration of harmful substances (vapours, gases, dust), it is usually possible to achieve a good sanitary and hygienic effect with a small amount of air removed.

However, local systems cannot solve all the problems facing ventilation. Not all harmful secretions can be localized by these systems. For example, when harmful emissions are dispersed over a large area or volume; air supply to certain areas of the room cannot provide the necessary conditions the air environment, the same if the work is done on the entire area of ​​​​the room or its nature is associated with movement, etc.

General exchange ventilation systems - both supply and exhaust, are designed for ventilation in the room as a whole or in a significant part of it.

General exchange exhaust systems relatively evenly remove air from the entire serviced premises, and general exchange supply systems supply air and distribute it throughout the volume of the ventilated room.

General supply ventilation.

General exchange supply ventilation is arranged to assimilate excess heat and moisture, dilute harmful concentrations of vapors and gases that are not removed by local and general exchange exhaust ventilation, as well as to ensure the calculated sanitary and hygienic standards and free breathing of a person in the working area.

With a negative heat balance, i.e., with a lack of heat, general exchange supply ventilation is arranged with mechanical stimulation and with heating of the entire volume of supply air. As a rule, before supplying the air is cleaned of dust.

When harmful emissions enter the air of the workshop, the amount of supply air must fully compensate for general and local exhaust ventilation.

General exhaust ventilation.

The simplest type of general exhaust ventilation is a separate fan (usually of an axial type) with an electric motor on one axis, located in a window or wall opening. Such an installation removes air from the room zone closest to the fan, performing only general air exchange.

In some cases, the unit has an extended exhaust duct. If the length of the exhaust duct exceeds 30-40 m and, accordingly, the pressure loss in the network is more than 30-40 kg / m2, then instead of axial fan a centrifugal fan is installed.

When harmful emissions in the workshop are heavy gases or dust and there is no heat from the equipment, exhaust ducts are laid along the floor of the workshop or made in the form of underground channels.

IN industrial buildings, where there are heterogeneous harmful emissions (heat, moisture, gases, vapors, dust, etc.) and their entry into the room occurs under different conditions (concentrated, dispersed, at different levels, etc.), it is often impossible to manage which - either by one system, for example, local or general exchange.

In such rooms, to remove harmful emissions that cannot be localized and enter the air of the room, general exchange exhaust systems are used.

In certain cases, in industrial premises, along with mechanical ventilation systems, systems with natural motivation are used, for example, aeration systems.

Channel and non-channel ventilation.

Ventilation systems have an extensive network of air ducts for moving air (duct systems) or channels (air ducts) may be absent, for example, when installing fans in a wall, in a ceiling, with natural ventilation, etc. (non-duct systems).

Thus, any ventilation system can be characterized according to the above four features: by purpose, service area, air mixing method and design.

Ventilation systems include groups of a wide variety of equipment:

• Fans.
  • axial fans;
  • radial fans;
  • crossflow fans.
• Fan units.
  • channel;
  • roof.
• Ventilation units:
  • supply;
  • exhaust;
  • supply and exhaust.
• Air-thermal curtains.
• Silencers.
• Air filters.
• Air heaters:
  • electrical;
  • water.
• Air ducts:
  • metal;
  • metal-plastic;
  • non-metallic.
  • flexible and semi-flexible;
• Locking and control devices:
  • air valves;
  • diaphragms;
  • check valves.
• Air distributors and air outlet control devices:
  • gratings;
  • slotted air distribution devices;
  • shades;
  • nozzles with nozzles;
  • perforated panels.
• Thermal insulation.