What is mechanical supply and exhaust ventilation. Ventilation systems: types, design, purpose. Mechanical supply ventilation systems

Mechanical ventilation systems are used where natural ventilation is insufficient. Mechanical systems use equipment and devices (fans, filters, air heaters, etc.) to move, purify and heat air. Such ventilation systems can remove or supply air to ventilated areas regardless of environmental conditions.

Mechanical ventilation systems can also be ducted or non-ducted. The most common are channel systems. The energy costs for their operation can be quite large. Such systems can supply and remove air from local areas of the room in the required quantity, regardless of changing environmental air conditions.

The advantage of mechanical ventilation over natural ventilation is the ability to provide stable required air exchange regardless of the time of year, external meteorological conditions, as well as wind speed and direction. It allows you to process the air supplied to the premises, bringing its meteorological parameters to the values required by the standard, and purify the air from harmful impurities before being released into the atmosphere. The disadvantages of a mechanical ventilation system include high energy costs, but these costs quickly pay off.

If the heat, moisture, gases, dust, odors or vapors of liquids released in the room enter directly into the air of the entire room, then general ventilation is installed. General exchange exhaust systems remove air relatively evenly from the entire serviced room, and general exchange supply systems supply air and distribute it throughout the entire volume of the ventilated room. In this case, the volume of exhaust air is calculated so that after replacing it with supply air, air pollution would drop to the maximum permissible concentration (MAC) values.

Typically, the same amount of air is extracted from the room as is supplied to it. However, there are cases when the total air flow is not equal to the exhaust. For example, from rooms where odorous substances or toxic gases are emitted, more air is extracted than supplied through the supply system, so that harmful gases and odors do not spread throughout the building. The missing volume of air is pumped through open openings in external fences or from neighboring rooms with cleaner air.

General supply ventilation

Supply systems serve to supply clean air to ventilated rooms to replace the removed air. If necessary, the supply air is subjected to special treatment (cleaning, heating, humidification, etc.).

The supply mechanical ventilation diagram (Fig. 1) includes: air intake device 1; air filter 2 ; air heater (heater) 3; fan 5; duct network 4 and supply pipes with nozzles 6 . If there is no need to heat the supply air, then it is passed directly into the production premises through bypass channel 7.

Premises can only be equipped with fresh air ventilation systems. In such cases, a calculated amount of air is supplied to the room. Air removal can occur in an unorganized manner through leaks in building fences or through openings specially provided for this purpose.

Rice. 1. Supply ventilation diagram

In a steady state, the amount of supply air is always equal to the amount of exhaust air, regardless of the total area of leaks or openings in building structures. As a rule, the cleanest rooms are equipped with supply systems, since the air moves from these rooms, and not vice versa.

Local supply ventilation

Local supply ventilation systems supply fresh air directly to the workplace or rest area. In the system's coverage area, conditions are created that differ from the conditions in the entire room and satisfy the requirements. Local supply ventilation includes air showers and oases. An air shower is a local air flow directed at a person. In the area of effect of the air shower, conditions are created that are different from the conditions in the entire volume of the room. With the help of an air shower, the following parameters can be changed: human mobility; temperature; humidity; concentration of one or another harmfulness. Air showers are most often used in hot shops, in workplaces exposed to thermal radiation.

Local supply ventilation also includes air oases - areas of premises fenced off from the rest of the room by movable partitions 2.0 - 2.5 meters high, into which air with a low temperature is pumped.

Local ventilation requires less cost than general ventilation.

General exhaust ventilation

Exhaust ventilation is used to remove contaminated or heated exhaust air from an industrial or residential premises (workshop, building). If premises are equipped only with an exhaust ventilation system, air is removed from the premises in an organized manner. The influx occurs unorganized or through leaks in building structures, or through openings specially provided for this purpose.

Exhaust ventilation (Fig. 2) consists of a cleaning device 1, a fan 2, a central 3 and suction ducts 4.

Unlike supply ventilation systems, in rooms with only exhaust systems, the pressure is set below atmospheric or lower than in neighboring rooms.

If there is only an exhaust ventilation system in the room, as in the case of supply ventilation, air flows from a zone of high pressure to a zone of low pressure. Thus, the movement of air in the opposite direction is eliminated or hampered. The most “dirty” rooms are equipped with exhaust ventilation systems when it is necessary to prevent or reduce the spread of air from them into neighboring rooms.

Rice. 2. Diagram of the exhaust ventilation system

Local exhaust ventilation

Local exhaust ventilation is used in a situation where the places where harmful substances are released 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, suspended matter and heat partially released from equipment. To remove harmful substances, local suction is used (shelters in the form of cabinets, umbrellas, side suction, shelters in the form of casings for machine tools, etc.).

Basic requirements that they must satisfy:

If possible, the place of formation of harmful emissions should be completely covered;

the design of the local suction must be such that the suction does not interfere with normal work and does not reduce labor 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 upward, cold heavy gases and dust - downward).

The air removed from the room during local exhaust ventilation must first be cleared of dust before being released into the atmosphere. The most complex exhaust systems are those that provide for a very high degree of air purification from dust with the installation of two or even three dust collectors (filters) in series.

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

Supply and exhaust ventilation

The supply and exhaust ventilation system is based on the creation of two counter flows. Such a system can be created either on the basis of independent air supply and exhaust subsystems - with their own fans, filters, etc., or on the basis of one corresponding installation operating both for supply and exhaust. The diagram of the supply and exhaust ventilation system is shown in Fig. 3.

Rice. 3. Supply and exhaust ventilation system: 1 - air distributors; 2 - air intake devices (grills); 3 - dampers; 4 - fan (supply, exhaust); 5 - filter; 6 - air heater; 7 - air valve; 8 - outer grille; 9 - exhaust hood; 10 - supply air duct; 11 - exhaust air duct

The convenience of such systems is not only in ease of installation and installation, but also in operation, as well as in the additional properties of such systems. One of these properties is heat recovery - a process in which a partial increase in the temperature of the supply air occurs due to the heat of the exhaust air. In this case, energy is spent only on organizing air flows, i.e. is not spent on heating the incoming air. Heating of incoming air due to recuperation can be supplemented by an electric or water heater. Supply and exhaust ventilation provides forced replacement of air in the room; performs the necessary air treatment (heating, purification); Some systems also provide air humidification within certain limits.

Composition of ventilation systems

The composition of the ventilation system depends on its type. Supply artificial (mechanical) ventilation systems are the most complex and frequently used, so it is their composition that we will consider.

Typically, a supply mechanical ventilation system consists of the following components (located in the direction of air movement, from inlet to outlet):

Air intake device. Air intake devices in mechanical ventilation systems are made in the form of holes in the fences of buildings, attached or free-standing shafts (Fig. 4).

When air is taken from above, air intake devices are placed in the attic or top floor of the building, and the channels are discharged above the roof in the form of shafts.

The location and design of air intake devices are selected to ensure the purity of the intake air and meet architectural requirements. Thus, air intake devices should not be located near sources of air pollution (emissions of polluted air or gases, chimneys, kitchens, etc.).

The height relative position of the inlet openings should be determined taking into account the volumetric mass of released contaminants. Openings for air intake should be placed at a height of more than 1 m from the level of stable snow cover, determined according to data from hydrometeorological stations or calculations, but not lower than 2 m from the ground level.

Fig.4. Air intake devices: A- in the outer wall; b- at the outer wall; V- on the roof

Architectural requirements are met by appropriate choice of hole location and design.

The outer walls of exhaust ducts and shafts are insulated to prevent condensation of water vapor from the extracted moist air and the formation of ice.

The speed of air movement in the supply channels and shafts is assumed to be within the range of 2 - 5 m/s, in the channels and shafts of exhaust devices - 4 - 8 m/s, but not less than 0.5 m/s, including for natural ventilation.

Air valve. To protect premises from cold outside air entering through ventilation ducts when ventilation is not working, air intake devices are equipped with multi-leaf insulated valves with manual or mechanical drive. In the latter case, the valve is blocked with the fan and closes the holes when it stops. At a low design temperature of the outside air, the valves are equipped with an electric heating system in order to protect their valves from freezing. Electric heating is turned on for 10-15 minutes before starting the fan.

Filter. An air filter is a device in ventilation systems that serves to clean supply air, and in some cases, exhaust air. The filter is necessary to protect both the ventilation system itself and the ventilated premises from the ingress of various small particles, such as dust, insects, fluff, etc. The design of the air filter is determined by the nature of the dust (pollution) and the required air purity.

Breakthrough coefficient (R,%) - characteristic of a filter or filter material, equal to the percentage of particle concentration after the filter WITH P WITH D

Efficiency (E,%) - characteristic of a filter or filter material, equal to the percentage difference in particle concentration to WITH D and after filter C P to the particle concentration before the filter WITH D

The most penetrating particle size is the particle size corresponding to the minimum efficiency of the filter material.

Filter performance (air flow) is the volume of air per unit time passing through the filter.

Aerodynamic resistance (pressure drop across the filter) is the difference in total pressure before and after the filter at a certain filter performance.

Filters are classified according to purpose and efficiency into:

general purpose filters - coarse filters and fine filters;

filters that provide special requirements for air purity - high-efficiency filters and ultra-high-efficiency filters.

Designations of filter classes are shown in table. 1.

Table 1

Designations of filter classes (GOST R 51251-99 )

Filter group	Filter class

Coarse filters
Fine filters
High efficiency filters
Ultra High Efficiency Filters
Notes 1 General purpose filters are used in any ventilation and air conditioning systems. 2 High and ultra-high efficiency filters ensure that special air cleanliness requirements are met, including in clean rooms.

The classification of general purpose filters is given in table. 2.

table 2

Classification of general purpose filters according to the efficiency of particles captured

Filter group	Average efficiency, %
Filter group	E c	E a
Coarse filters	E With < 65
	65 ≤ E With < 80
	80 ≤ E With < 90
	90 ≤ E With
Fine filters		40≤ E a < 60
		60 ≤ E a < 80
		80 ≤ E a < 90
		90 ≤E With < 95
		95 ≤ E a
Designations: E c . - efficiency determined from synthetic dust by the gravimetric method (by the difference in the mass concentration of particles before and after the filter); E A - efficiency determined by atmospheric dust.

Structurally, filters are divided into roll filters (non-woven filter material is used), cell filters (metal mesh, vinyl plastic mesh, foam rubber, and special material such as FPP are used).

Pocket-type filters FYaK purification class G3-F9 are designed to clean air from dust from external recirculated air in supply ventilation and air conditioning systems. Filters are manufactured according to TU 4863-015-04980426-2003, GOST R 51251-99. FyaK can be operated at operating temperature from minus 40 °C to plus 70 °C. The environment and filtered air must not contain aggressive gases and vapors.

The filter (Fig. 1) consists of a metal frame 1 and filter material sewn in the form of pockets 2.

Rice. 1. Pocket filter FyaK

The opposite surfaces of the pockets are tightened with limiters, which prevents strong swelling and sticking together of adjacent pockets. At the end of the pockets there is a braid 3, with the help of which the pockets are connected to each other and do not “fly apart” under the pressure of the air flow. The filter pockets are made of high quality synthetic filter material.

The sizes of the pockets are selected so that the air flow is uniform over the entire surface of the filter. The special shape of the pockets allows them to inflate without touching each other, dust accumulates evenly over the entire surface of the pockets and every square centimeter of filter material is optimally used.

Pleated cell filters of the FyaG type are designed for cleaning external and recirculated air in supply ventilation and air conditioning systems for premises for various purposes in domestic, administrative and industrial buildings. FyaG filters (Fig. 2) consist of a frame (1) made of cardboard or galvanized steel, inside of which filter material (2) is laid in the form of corrugations, resting on the air outlet side on a corrugated (wavy) mesh (3).

Rice. 2. FyaG filter circuit

To eliminate unpleasant odors in residential areas, filters made of a material with an ultramicroscopic structure are used, which makes it possible to extract gases from the air. The most common absorber of gases, vapors and odors is activated carbon.

Mechanical ventilation systems use equipment and devices (fans, electric motors, air heaters, dust collectors, automation, etc.) that allow air to be moved over significant distances. The energy costs for their operation can be quite large. Such systems can supply and remove air from local areas of the room in the required quantity, regardless of changing environmental air conditions. If necessary, the air is subjected to various types of processing (cleaning, heating, humidification, etc.), which is practically impossible in systems with natural impulse.

Rice. 3.2. Mechanical ventilation unit.

It should be noted that in practice, so-called mixed ventilation is often provided, that is, both natural and mechanical ventilation. In each specific project, it is determined which type of ventilation is the best in sanitary and hygienic terms, as well as economically and technically more rational.

Forced ventilation

Supply systems serve to supply clean air to ventilated rooms to replace the removed air. If necessary, the supply air is subjected to special treatment (cleaning, heating, humidification, etc.)

Exhaust ventilation

Exhaust ventilation removes polluted or heated exhaust air from the room (workshop, building). In general, both supply and exhaust systems are provided in the room. Their performance must be balanced taking into account the possibility of air flow into or from adjacent rooms.

The premises may also have only an exhaust or only a supply system. In this case, air enters this room from the outside or from adjacent rooms through special openings, or is removed from this room to the outside, or flows into adjacent rooms. Both supply and exhaust ventilation can be installed at the workplace (local) or for the entire room (general).

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 ventilation requires less cost than general ventilation. In industrial premises, when hazardous substances (gases, moisture, heat, etc.) are released, a mixed ventilation system is usually used - general to eliminate hazardous substances throughout the entire volume of the room and local (local suction and influx) to service workplaces.

air showers(concentrated air flow at increased speed). They must supply clean air to permanent work areas, reduce the ambient temperature in their area, and provide ventilation to workers exposed to intense heat 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 pumped.

Local supply ventilation is 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 exhaust ventilation

Local exhaust ventilation is used when the places where harmful substances and emissions are released in the room are localized and their spread throughout the room can be prevented. Local exhaust ventilation in industrial premises ensures the capture and removal of harmful emissions: gases, smoke, dust and heat partially released from equipment. To remove harmful substances, local suction is used (shelters in the form of cabinets, zones, side suctions, curtains, shelters in the form of casings for machine tools, etc.) Basic requirements that they must satisfy:

If possible, the place of formation of harmful secretions should be completely covered.

The design of the local suction must be such that the suction does not interfere with normal operation and does not reduce labor 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 upward, cold heavy gases and dust - downward).

The designs of local suction systems are conventionally divided into the following groups:

Semi-open exhaust hoods (fume hoods, see Fig. 3.3).

Fig.3.3. Half-open suctions.

Open type (on-board suction). Removal of harmful emissions is achieved only with large volumes of sucked air (Fig. 3.4).

Fig.3.4. Onboard suctions.

Umbrella-visors for heating furnaces: a) at the slot opening when combustion products are released from it; b) at an opening equipped with a door for the release of combustion products through gas windows.

A system with local suction is shown in Fig. 3.5.

Fig.3.5. Local suctions.

The main elements of the system (Fig. 3.5) are local suction - shelters (MO), a suction network of air ducts (VN), a centrifugal or axial fan (V), (VSh) - an exhaust shaft.

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

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

However, local ventilation systems cannot solve all the problems facing ventilation. Not all harmful emissions can be localized by these systems. For example, when harmful emissions are dispersed over a large area or volume, the air supply to individual rooms cannot provide the necessary air conditions. The same applies if the work is carried out over the entire area of the room or its nature is associated with movements, etc.

General ventilation

General ventilation systems - both supply and exhaust, are designed to provide ventilation in the room as a whole or in a significant part of it. General exchange exhaust systems remove air relatively evenly from the entire serviced room, and general exchange supply systems supply air and distribute it throughout the entire 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 not removed by local and general exchange exhaust ventilation, as well as to ensure the calculated standards and free breathing of a person in the work area.

With a negative heat balance, that is, with a lack of heat, general supply ventilation is arranged with mechanical stimulation and heating of the entire volume of supply air. As a rule, the air is cleaned of dust before being supplied. When harmful emissions enter the workshop air, 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 axial type) with an electric motor on a single axis (Fig. 3.6. A), located in a window or wall opening.

Fig.3.6. The simplest exhaust ventilation schemes: 1- insulated valve; 2- fan; 3- fan blades; 4-exhaust shaft; 5- gate; 6- electric motor; 7-exhaust air duct network.

This installation removes air from the area of the room closest to the fan, performing only general air exchange. In some cases, the installation has a long exhaust duct. If the length of the exhaust air duct exceeds 30-40 m and, accordingly, the pressure loss in the network is more than 30-40 kg/sq.m., then a centrifugal type fan is installed instead of an axial fan.

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

In industrial buildings where there are various harmful emissions (heat, moisture, gases, vapors, dust, etc.), and their entry into the premises occurs under different conditions (concentrated, dispersed, at different levels, etc.), It is often impossible to get by with any one system, for example, local or general exchange. In such premises, general exhaust systems are used to remove harmful emissions that cannot be localized and enter the room air. In certain cases, in industrial premises, along with mechanical ventilation systems, systems with natural impulse are used, for example, aeration systems.

Duct and ductless ventilation

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

Mechanical ventilation more advanced compared to natural ventilation, but requires significant capital and operating costs.

Mechanical ventilation ensures that incoming air is taken from places where it is cleanest; allows air treatment - heating, humidification or drying; allows you to supply air to any workplace or equipment, as well as remove it from any place with cleaning. Cleaning the exhaust air to prevent air pollution is important, since Soviet legislation strictly protects the cleanliness of the atmosphere in cities and towns. Mechanical ventilation can be performed in the form of supply, exhaust or supply and exhaust. To ensure normal meteorological conditions in industrial premises, when designing industrial enterprises, along with natural ventilation, mechanical ventilation is provided.

With mechanical ventilation, air exchange is achieved using a fan. Therefore, this type of ventilation allows you to change the parameters of the air entering the room - heat, cool, dry and humidify, as well as purify polluted air emitted into the atmosphere. ventilation air recirculation

According to the place of action, mechanical ventilation is divided into:

- general exchange;
- local.

General ventilation designed to reduce the concentration of harmful impurities in the volume of the entire room to a standardized value. It can be supply, exhaust and supply and exhaust.

The most effective is supply and exhaust ventilation(diagram 1), consisting of two separate systems - supply and exhaust, which simultaneously supply clean air into the room and remove polluted air from it.

Scheme 1. Supply and exhaust ventilation with air recirculation: a - supply system; b - exhaust system; 1 - air intake device; 2 - air purifier; 3 - centrifugal fan; 4 - heater; 5 - humidifier-cooler; 6 - distribution pipeline; 7- supply nozzles; 8 - local suction; 9- dust collector; 10- ejection device; 11 - air duct; 12- valves; 13 - production premises; 14 - fan

Supply and exhaust systems in the room must be placed so that fresh air enters those parts of the room in which the amount of harmful emissions is minimal or completely absent, and the exhaust system is installed where emissions are maximum.

Natural ventilation, depending on the outside temperature and wind speed, cannot always provide the necessary air exchange. Therefore, where it is necessary to remove a strictly defined amount of air from a room and replace it with the same volume, mechanical ventilation is widely used.

With mechanical ventilation, the required amount of air at a predetermined temperature and humidity is supplied to the workshop or directly to the workplace in order to provide conditions for a normal technological process or to meet the requirements of sanitary standards.

Exhaust mechanical ventilation systems remove dusty or gas-contaminated air at any distance from the workplace or workshop, and also clean the air of dust before releasing it into the atmosphere. Supply and exhaust systems can be turned on and off at any time, their operation is controlled by maintenance personnel. Due to these advantages, mechanical ventilation is more widely used than natural ventilation.

General supply ventilation

Supply systems serve to supply clean air to ventilated rooms to replace the removed air. If necessary, the supply air is subjected to special treatment (cleaning, heating, humidification, etc.).

Rice. 1. Supply ventilation diagram

With all the variety of ventilation systems, due to the different purposes of premises, the different nature of technological processes, types of harmful emissions and other factors, they can be classified according to the following criteria:

Depending on what method of creating pressure for ventilation processes is used. They can be with natural or mechanical motivation.
Depending on the purpose, the system can be supply, exhaust or supply and exhaust.
Depending on the area served by the system - local and general exchange.
Depending on the design, ventilation can be ducted or non-ducted.

Considering these varieties, various combinations of ventilation systems are possible. For example, a general exchange duct system with supply and exhaust ventilation and mechanical drive (this is a standard ventilation used for large climate systems) or a ductless local exhaust ventilation system with natural drive (this is air exhaust without the use of a fan, working naturally by air convection).

Natural ventilation

This type of ventilation works thanks to:

temperature differences between ambient air and indoor air (aeration);
the difference in pressure of the air column between the serviced room and the exhaust device;
influence of wind pressure.

Aeration is used in workshops with large heat releases, provided the permissible concentration of harmful gases and dust in the supply air in the work area is not exceeded.

Aeration is not used if, according to the conditions of the workshop technology, it is necessary to pre-treat the supply air or if condensation or fog is formed due to the influx of atmospheric air.

In ventilation systems in which air moves due to the pressure difference of the air column, the height difference (minimum) between the level of internal air intake and its outlet through the exhaust device must be at least 3 m.

The recommended horizontal length of air duct sections should not be more than 3 m, and the speed of air movement in the air duct should not exceed 1 m/sec. If these requirements are not met, ventilation will simply not work effectively.

The effect of wind pressure is expressed in the fact that on the windward sides of the building (facing the wind) increased pressure is formed and, conversely, on the leeward sides - decreased (rarefaction).

If there are openings in the building enclosures, then the outside air enters the room from the windward side and leaves it from the windward side, while the speed of its movement in the openings depends on the speed of the wind blowing the building and, accordingly, on the difference in pressure that occurs.

The natural ventilation system is simple and does not require electricity or expensive equipment. But since the efficiency of using this system depends on external variable factors (air temperature, wind direction and speed), more complex functions in the field of ventilation cannot be solved with their help.

Mechanical ventilation

These ventilation systems use equipment and devices (electric motors, dust collectors, air heaters, automation, etc.) that allow air masses to be moved over long distances.

The electrical energy consumption for operating this equipment is usually quite high.

Thanks to mechanical ventilation, air can be supplied and taken in the required quantity from local areas of the room, regardless of changing atmospheric conditions outside the building. If necessary, the air can be subjected to various processing methods (cleaning, humidification, heating, etc.), which is impossible in a system with natural impulse.

It should be noted that very often in practice so-called combined ventilation is provided - this is the simultaneous use of natural and mechanical systems. This can significantly improve ventilation efficiency and reduce resource costs.

Forced ventilation

Supply ventilation serves solely to supply air masses into the ventilated room. If necessary, the air is subjected to special treatment before it is supplied to the room - humidification, purification, heating, cooling, etc. Its removal occurs due to the occurrence of excess pressure in which excess air is displaced and replaced with fresh air. Air leaves the room through opening doors and leaks in building envelopes.

Exhaust ventilation

The task of exhaust systems is to remove contaminated or heated treated air from a room (production, workshop, building) to create a vacuum in it. Due to rarefaction, outside air enters through the doors and leaks in the enclosures.

Supply and exhaust ventilation

Depending on the desired effect, only a supply system or only an exhaust system can be used. But in most cases, both systems are provided in the premises at once.

Using supply and exhaust equipment, room ventilation has the following advantages:

there is no residual pressure in the ventilated room;
there are also no drafts.

On the one hand, this type of ventilation is quite powerful and is capable of providing the necessary air exchange. On the other hand, air handling units are not very expensive in terms of electrical energy consumption and operating costs.

General and local ventilation

The purpose of general ventilation— ensuring air exchange throughout the room. With such a system, all the necessary air mass parameters are maintained throughout the entire volume of the room. In addition, its tasks include the removal of pollutants, excess heat and humidity that were not eliminated by local ventilation to the permitted standard.

The local ventilation system is as follows: clean air is supplied to specific places (this is supply ventilation), and polluted air is removed only from places where unacceptable harmful emissions are formed (this is exhaust ventilation). Such a system can be suitable for a large room with a small number of people in it; in this case, air exchange is carried out only in areas where working people are located.

Duct and ductless ventilation systems

Ventilation systems may have a large, extensive network of channels (ducts) that are designed to move air. Such a system is called a channel system. Also, these channels may be absent, in which case the ventilation is called ductless.

Installation of a system with a channel network is used mainly in large rooms. As for ductless, it is used when installing small-sized systems, for example, a home fan.

The choice of ventilation system should be made at the design stage of the building (structure). And this, of course, should be done by professionals.