WO1991014827A1

WO1991014827A1 - Method and installation for air treatment in the area of a traffic route for motor vehicles

Info

Publication number: WO1991014827A1
Application number: PCT/SE1991/000230
Authority: WO
Inventors: Anders Krantz
Original assignee: Airchitect I Söderhamn Ab
Priority date: 1990-03-29
Filing date: 1991-03-27
Publication date: 1991-10-03
Also published as: SE9001155D0; SE9202801D0; SE9202801L; EP0555217A1; AU7560591A

Abstract

An installation for air treatment in the area of a traffic route for motor vehicles (30) emitting air-polluting exhaust gases comprises an elongate shell (1) which completely or partly encapsulates the traffic route and in which outlets (19) are arranged for evacuating the air present in the shell and polluted by the exhaust gases from the vehicles passing through the shell. The outlets (19) communicate with filters (22) positioned in air treatment stations (11) spaced from each other in the longitudinal direction of the shell, for cleaning the exhaust air before it is discharged into the atmosphere.

Description

METHOD AND INSTALLATION FOR AIR TREATMENT IN THE AREA

OF A TRAFFIC ROUTE FOR MOTOR VEHICLES

Field of the Invention This invention relates to a method for air treatment in the area of a traffic route for motor vehicles emitting air-polluting exhaust gases, comprising the steps of first completely or partly encapsulating the traffic route in an elongate shell, and thereafter evacuating the air present in said shell and polluted by the exhaust gases from the vehicles passing through the interior of the shell. Description of the Prior Art

In many densely built-up areas, motorism is a grow¬ ing problem, not only because of the difficulties of con- trolling the traffic and of providing sufficient space for it, but also because of the air pollution problems involved. Thus, today's gasoline- and diesel fuel-powered motor vehicles emit substantial quantities of exhaust gases constituting a serious health hazard to all living beings, including man, and having a destructive polluting impact on the local environment. These air pollution pro¬ blems become especially noticeable when an urban area, e.g. a town, is intersected by a main road or other major thoroughfares, or through routes, which at times are heavily trafficked not only by private cars, buses and other local vehicles, but also by heavy-duty road vehicles with high fuel consumption. These problems become the more pronounced if the urban area - while having one or more busy through routes - is situated on a low level in rela- tion to its surroundings, e.g. in a valley surrounded by mountains. In such cases, the exhaust gases will accumu¬ late, especially when the weather is bad, at the bottom of the valley from where they cannot be efficiently dispersed and thinned by the ambient atmosphere. As a result, the concentration of noxious constituents in the air will rise far above maximum permissible values. Thus, the people living in such urban areas are subjected at times to a very heavy pollution strain.

Town planners and politicians are now looking for effective solutions to the problems related above. A natural solution to these problems in urban areas with heavily trafficked through routes is to relocate these routes outside the central area so as to divert at least the through traffic, thus reducing exhaust gas emissions. Theoretically, this solution may in some cases be con- sidered an acceptable solution of the acute air pollution problems in urban areas, but many times it cannot be put into practice because of the extremely high costs in¬ volved. Relocating an existing through route from a medium-size urban area (with 50,000-200,000 inhabitants) to a place at a safe distance therefrom, may thus easily involve costs of several billions of Swedish crowns. Besides, this alternative is not an ideal solution since much of the local traffic will be concentrated on the old through route, which means that the amount of air pollu- tions in the area of this route may remain very consider¬ able. Also, the indicated solution is less attractive when taking into account that vehicles such as light pri¬ vate cars, buses and heavy-duty goods vehicles are likely in the near future to be powered other than by exhaust- producing internal combustion engines. In the long run, the construction of new expensive by-pass routes may thus prove to be a bad investment for society. Last, but not least, remains the irrefutable fact that the solution now described will not overcome the problem of an increasing total amount of air pollutions with increasing traffic intensity.

In order to solve the above-mentioned problems, it has been suggested in DE-OS-2,509,279 to encapsulate heavily trafficked through routes in a covering shell, in the roof of which are mounted ventilating units, each containing a motor-powered fan. By means of this fan, it is possible either to blow outdoor air into the space defined by the shell or, by reversing the fan motor, to exhaust air from the interior of the shell to evacuate it into the ambient atmosphere. Irrespective of the direc¬ tion in which the air is passed through the ventilating unit, it will not be treated in any way whatever. The inventive concept disclosed in DE-OS-2,509,279 thus resides in replacing conventional, axially-feeding so- called air jet ventilators of the type used in tunnels, with a transverse-feed system in which the ventilating units suck in and/or blow out air at spaced locations along the shell instead of blowing air from end to end as is the case in air jet ventilating arrangements used in tunnels. The solution suggested in DE-OS-2,509,279 does not pay any regard whatever to the local environment out- side the covering shell, since the polluted air produced by the vehicles passing through the interior of the shell is directly exhausted into the ambient atmosphere without being treated in any respect. This means that only the environment in the shell is improved, whereas the ambient atmosphere is subjected to exactly the same air pollution strain as were the traffice route completely open or without any encapsulation. Summary of the Invention

The present invention aims at solving the above-dis- cussed problems in an entirely new way at a cost consider¬ ably below the costs for constructing new by-pass routes. A basic object of the invention thus is to provide means for drastically reducing the amount of air pollution in the vicinity of a traffic route for motor vehicles. Another object is to implement this basic object by means considerably less expensive than relocating traffic routes. A further object is to eliminate, or at least sub¬ stantially reduce, the traffic noise generated in the vicinity of heavily trafficked arterial roads. Also, it is an object of the invention to create an architectonically attractive environment in conjuction with a traffic route. Further, it should be possible to utilise the last-men- tioned two objects, when implemented, for achieving an improved living environment in the immediate vicinity of the traffic route. Yet another object of the invention is to create an improved environment along the traffic route, with enhanced road safety and improved travelling comfort as a result.

According to the invention, these and other objects are achieved by a method characterised more specifically by causing the evacuated exhaust air to pass through fil- ters in which it is cleaned before being discharged into the atmosphere.

In addition to the method, the invention also relates to an installation for air treatment in the area of an arterial road. The features of this installation appear from the accompanying subclaims 4-16. Description of other Prior Art

From EP 0,237,625 it is previously known to use an air jet type ventilating system for tunnels of the type comprising a number of spaced-apart air jet ventilators mounted in the tunnel and serving to produce an axial air flow from one end of the tunnel to the opposite end there¬ of. Although some of these air jet ventilators include filters for filtering the air, they are in practice so- called smoke eaters drawing in polluted air in one end and blowing out filtered in the other end. It is true that the smoke eaters filter a certain quantity of the polluted air produced by vehicles passing through the tunnel, but in practice the air blown out at the other end of the tunnel will in all likelihood be highly polluted, since the indi- vidual smoke eaters do indeed not have the capacity to almost completely clean the entire amount of air passing through the tunnel. Thus, such smoke eaters can only affect a fraction of the entire flow of air passing through the tunnel. As opposed to the tunnel ventilating system described in EP 0,237,625, the present invention is based on the idea that the polluted air in a road-covering shell should be evacuated through a plurality of spaced-apart air treatment stations which are provided with filters and each serve only a quite short section of the road, more specifically in such a manner as to evacuate the exhaust air in this road section through the filters arranged in the air treatment station concerned, before the air is discharged into the atmosphere. Thus, no axial feed of the air takes place from one end of the shell to the other, which means that substantially all the air which is eva- cuated from the shell will be practically completely cleaned. It is only by such a solution that the basic problem can be considered to have been adequately solved.

In this context, it should also be emphasised that the device of EP 0,237,625 is not devised for solving the air pollution problems existing in conventional open roads or traffic routes, since it does not state or even suggest the idea of encapsulating a traffic route in a special shell.

Brief Description of the Drawings In the drawings,

FIG. 1 is a schematic top plan view of part of an installation according to the invention, FIG. 2 is an enlarged cross-section taken along the line II-II in Fig. 1, FIG. 3 is a side view of an exhaust air treatment station included in the installation, FIG. 4 is a perspective view of the station shown in

Fig. 3, FIG. 5 is an enlarged cross-section taken along the line V-V in Fig. 1, and

FIG. 6 is a top plan view of an alternative embodiment of the installation according to the invention. FIG. 7 is a perspective view of a road-covering instal¬ lation according to the invention combined with a housing area,

FIG. 8 is a schematic view of a heat exchanger unit included in the installation of Fig. 7, and FIG. 9 is a cross-section showing a further alternative embodiment of the invention. Description of the Preferred Embodiment

In Figs 1-5, an elongate shell generally designated 1 is adapted to encapsulate or enclose a traffic route, pre¬ ferably a thoroughfare or through route, which is gene¬ rally designated 2 and in known manner includes two paral¬ lel roadways 2', 2" for traffic travelling in opposite directions. The shell 1 (see especially Figs 2 and 5) com- prises two separate, substantially vertical outer walls 3, 4 located on both sides of the traffic route 2, and a roof generally designated 5 including at least two slanting roof panels 6, 7 converging into a common ridge 8. In the illustrated embodiment, the shell also comprises a parti- tion 9 defining, together with the roof and the outer walls, two separate spaces or compartments 10, 10', one for each roadway 2', 2". In practice, the shell can be constructed in many different alternative ways. One con¬ ceivable, preferred alternative is to erect a framework of metal sections, e.g. aluminium sections, and cover the framework with panels, at least some of which, especially the wall-forming panels, are transparent, consisting e.g. of thermosetting plastic. Preferably, both the wall panels and the roof panels are made of transparent material to create an impression of spaciousness.

The shell 1 may have a highly varying length. How¬ ever, it should always extend along the stretch of a traffic route which runs through the centre of the urban area. Preferably, the shell however extends from the point of entry of the traffic route into the urban area to its point of exit therefrom. In actual practice, the shell may thus have a length of several kilometres or more. At points where other traffic routes intersect the main route over which the shell is placed, there are pro- vided suitable openings in the outer walls of the shell to permit vehicles to enter or leave the main route, and also to permit vehicles crossing the main route to pass straight through the shell. The major part of the traffic will however run in the elongate shell covering the main route 2.

As shown in the top plan view of Fig. 1 , there are provided, in the longitudinal extent of the shell, a plu¬ rality of spaced-apart treatment stations 11 for cleaning exhaust air sucked off from the interior of the shell. In practice, the distance between the treatment stations 11 should be in the range of 50-200 m, suitably 75-100 m. With particular reference to Figs 2-4, a separate treatment station 11 will now be described. The station comprises a house generally designated 12 which, in the illustrated embodiment, is mounted at the roof 5 of the shell. By means of a roof-structure like partition plate 13, the house 12 is divided into an upper chamber 14 and a lower chamber 15. At the bottom, the lower chamber 15 is defined by two inclined panels or metal sheets 16, 16' converging into a duct 17 defined by two vertical walls 18, 18'. The walls 18, 18', which are parts of the above- mentioned partition 9, terminate at a certain distance above the roadways 2', 2", thus forming an outlet 19 for sucking off exhaust air from the interior of the shell. Although the duct 17 in the illustrated embodiment opens into a single downwardly-facing outlet, the walls 18, 18' may extend as far as the roadway, in which case the out¬ lets or exhaust openings are provided in each of the two opposing walls 18, 18'. The lower chamber 15 is also pro¬ vided with outlets 20, 20' arranged at the end walls of the house and serving to suck off exhaust air from the interior of the shell at relatively elevated points, more specifically from air currents flowing substantially in the longitudinal direction of the shell. In this case, the upper chamber 14 is provided with two containers or cas¬ ings 21, 21' each comprising two sets of filters 22, 22'. Advantageously, these filters may be of the type described in W084/04467 and consist of tubes containing in known manner a plurality of strips having a prefiltering func- tion. Exhaust air is supplied to the casings 21, 21' from the lower chamber 15 through grilles or openings 13' in the partition plate 13 and is caused to pass through the filters 22 in an outward direction, leaving through the cylindrical walls of the filters, such that pollutants in the air are deposited in the interior of the filter tubes. The air then passes through the filter tubes 22' in an inward direction such that air pollutants are deposited on the outside of the filter tubes. The filter tubes 22' may contain different types of absorbents, such as active car- bon or grains of the PURAFIL type. The exhaust air is sucked into the house and through the filter containers by means of one or more fans 23 arranged in the area between the filter containers 21, 21'. When the exhaust air has been sucked by the fans 23 through the filters 22, 22' and thus been cleaned, it is discharged into the atmosphere outside the shell, e.g. through chimney-like evacuation ducts 24.

To supply fresh air into the interior of the shell for replacing the exhaust air sucked off through the filters 22, 22' and cleaned therein, inlets are provided in the outer walls 3, 4 of the shell. More specifically, each of the outer walls 3, 4 is provided with both a lower inlet 25 and an upper inlet 26. In practice, each of the inlets 25, 26 may advantageously be equipped with one or more dampers 27 for controlling the amount of sup¬ ply air drawn into the shell from outside. By the pre¬ sence of inlets both at the bottom and at the top of the outer walls, there is produced in each of the two spaces or compartments of the shell, not only a lower air cur¬ rent flowing directly from a lower inlet 25 to the outlet 19 located at the bottom of the partition, but also an upper, substantially arcuate air current flowing through the upper portion of each compartment, more specifically from the upper inlet 26 to the outlet 19 at the bottom of the partition. The flow pattern is indicated by arrows in Fig. 2. As illustrated in Fig. 1, at least the upper supply air inlets 26 extend only in the area between adjacent exhaust air treatment stations 11, while the lower inlet 25 suitably extends throughout the entire length of the shell 1. The supply of fresh air into the interior of the shell normally takes place by natural ventilation, i.e. fresh air is automatically sucked from outside into the interior of the shell as a result of the negative pressure produced by the evacuation of exhaust air by means of the fans 23. In case the exhaust fans 23 should unintentional¬ ly stop functioning, two measures have been taken to avoid that poisonous exhaust gases remain in the shell. First, the roof 5 is provided with doors 28 (see Fig. 5) which can be automatically opened as soon as the content of air pollutants in the interior of the shell exceeds a certain threshold value, for temporarily discharging the polluted air without being cleaned so as to reduce the amount of air pollutants in the shell. Secondly, independently ope¬ rating fan blowers 29 are evenly distributed along the length of the shell and serve to positively blow supply air into the interior of the shell in such cases of emer¬ gency when the evacuation doors 28 have been opened. The fan blowers 29 are suitably connected through ducts (not shown) to the above-mentioned supply air inlets. The installation described above operates in the following manner. Air charged with pollutants from the exhaust gases emitted by vehicles 30 travelling through the shell is sucked off from the two shell spaces or com¬ partments 10, 10', both through the outlet 19 at each treatment station 11 and through the outlets 20, whereupon the thus evacuated exhaust air is caused, as described above, to pass through the filters 22, 22' and eventually be discharged into the ambient atmosphere in the cleaned state. Since the outlets 19 at the different stations 11 are located on a low level, i.e. adjacent the roadway, the flow of exhaust air being sucked off will also efficiently entrain gases and constituents, such as sulphur dioxide, carbon dioxide (destroying the ozone layer), nitric oxide, nitrogen dioxide, lead etc., which are contained in the exhaust gases from the vehicles and which are heavier than the air. In this manner, no layer of heavy gases or con- stituents will be left on the roadway/roadways. While the polluted exhaust air is evacuated from the interior of the shell, fresh air is supplied from outside through the inlets 25, 26, it being possible to control the supply of fresh air thanks to the provision of the dampers 27 of these inlets. More precisely, such a control can be per¬ formed individually for the two air currents (upper and lower) established in each of the two compartments of the shell.

In practice, it is of course possible to equip the installation now described with a number of supplementary means in addition to those mentioned above. Thus, guard rails 32 for preventing vehicles from running into the shell walls can be arranged in association with the road¬ ways 2', 2". Further, it is conceivable to provide elec- trie heating in the roof 5 of the shell, e.g. electic resistance wires, serving to heat, as desired, the roof panels to remove snow and ice therefrom. For this purpose, the roof base can be specially designed such that melted snow and ice can be taken care of immediately so as not to drop onto pavements outside the shell.

Fig. 6 illustrates an alternative embodiment of the inventive installation. In this case, the shell 1' has four arms or branches 33, 33', 33", 33'" extending sub¬ stantially at right angles to each other and merging into a central shell portion 34. Depending on the length of the individual arms 33, one or more exhaust air treatment sta¬ tions 11 can be provided in the installation. In the illu¬ strated embodiment, the arms are assumed to have such a length that each arm requires a treatment station of its own. For shorter arms, it is conceivable to use only one treatment station arranged at the central portion 34. The illustrated installation is intended for use in connection with an intersection with heavy traffic where idling is frequent.

It is also conceivable to design the shell shown in Figs 1-5 in a manner analogous with that of the embodiment shown in Fig. 6. Thus, transverse arms or branches can be connected to the elongate shell in Figs 1-5 at intersect¬ ing streets or roads.

Fig. 7 illustrates an embodiment in which the road- encapsulating shell 1 is partly covered with a number of buildings 35, 35' which in practice can advantageously have the shape of dwelling houses and/or office buildings. The free space which is formed above the finished road- encapsulating shell 1 can thus advantageously be used to construct useful buildings, which can be done because the air in the area of the traffic route concerned is filtered and cleaned. In such embodiments, it is conceivable to build in the air treatment stations included in the inven¬ tive installation in one or more bridging houses, although it is still possible to arrange the stations in separate houses 12 as described above.

Fig. 8 illustrates how an air treatment station included in the inventive installation can be advan¬ tageously integrated in a building connected to the road- encapsulating shell. In the Figure, a schematically shown outer wall of e.g. the building 35 is designated 36. The road-encapsulating shell 1 formed under the building and covering the traffic route or roadway 2 includes an exhaust air outlet 19' which communicates with an air treatment station generally designated 11' . An outdoor air intake is designated 37 through which fresh air can be drawn in from outside and be supplied by a fan 38 as sup¬ ply air into the interior of the building via a piping system designated 39. The passage or duct through which the outdoor air passes is designated 40. In this duct there is mounted a set of filters 41 (one or more fil¬ ters), for example of the type described above and dis¬ closed in W084/04467. A second passage or duct 42 intersecting the duct 40 is arranged to carry exhaust air from the interior of the shell 1 through an outlet 43 to the ambient atmosphere. In this second air duct 42 are arranged suitably cylinder- shaped casings 44 (e.g. cylindrical, thin metal sheets) enclosing the filters 41. The duct 42 accommodates a second set of filters 41' which are also enclosed by cas¬ ings 44'. In both cases, the casings 44, 44' are spaced from the actual filters, thereby forming between each casing and filter an air gap through which the air that has passed through the filters can flow. A second fan 45 sucks in the exhaust air from the interior of the shell 1 and expels it into the duct 42. Before the exhaust air reaches the fan 45 and the filters 41, respectively, it will be cleaned in the filters 41' . The exhaust air dis¬ charged from the interior of the shell 1 normally has a considerably higher temperature than the outdoor air drawn in through the intake 37, at least in the cold time of the year. By means of the arrangement shown, the com- paratively cold outdoor air which passes through the fil¬ ters 41 and is cleaned therein will be preheated by heat transfer through the casings 44 which enclose the filters, since the exhaust air flowing along the casings 44 has a higher temperature than the air in the duct 40. In this context it should be emphasised that the air currents in the two ducts 40 and 42 are completely isolated from one another, whereby no mixing of air can take place.

By means of the arrangement illustrated in Fig. 8, the heat content of the air from the interior of the shell 1 can thus advantageously be used to preheat the supply air which is later, in the clean, tempered state, distri¬ buted to the different rooms in the building.

The air passing through the duct 42 is discharged into the ambient atmosphere, directly or indirectly, through the outlet 43. The air has been cleaned by passing through the special exhaust air filters 41' . Fig. 9 illustrates an embodiment in which the shell 1 is provided with one or more inlets 46 located on a low level and adapted to supply comparatively clean outdoor air into the interior of the shell. More specifically, this outdoor air is blown in by means of a special supply fan 47 which draws in fresh air from outside via an intake 48 and conveys the air to the inlet 46 through a conduit 49. Thus, this supply of air is effected by the active assistance of the fan 47, contrary to the inactive supply of fresh air by natural ventilation which takes place in the embodiment illustrated in Figs 2-5. By this supply of fresh air, the polluted air inside the shell is of course thinned, while lowering the content of poisonous or nox¬ ious constituents. The exhaust air from the interior of the shell is evacuated through two different types of out¬ let, viz. a first type 19 which is located on a low level in the shell for evacuating heavy gases or constituents in the air, such as C0₂, ^N0 _/ S0₂ etc., and a second type 20 which is located on a high level in the shell for evacuat- ing lighter gases or constituents. The exhaust air can be evacuated through silencers 50. The thus discharged exhaust air is evacuated by means of the exhaust fan 23 after first having passed a set of filters 22 in the man¬ ner described above. For the sake of simplicity, the inlet 46 and the two outlets 19, 20 have been shown in one and the same plane of the drawing. In actual practice, the inlet 46 can how¬ ever be axially displaced relative to the outlets 19, 20, for example in such manner that inlets are arranged in the area about midway between two treatment stations and their outlets, which are spaced apart in the longitudinal direc¬ tion of the shell. If the treatment stations and their outlets 19, 20 thus are positioned e.g. 100 m from one another, the inlet 46 can be located about 50 m from each station. In this manner, the polluted air will be thinned by means of fresh air in a particularly efficient manner. It should be pointed out in this context that the term "air treatment station" should be interpreted in its widest sense, since a set of filter elements 22 and the associated exhaust fan 23 can be common to two or more axially spaced outlets or evacuating positions, the air being transported between the outlets and the set of fil¬ ters through suitable ducts. Analogously, the exhaust fan 47 can be common to two or more axially spaced inlets 46 and connected therewith by means of longitudinal ducts. The invention offers several advantages. Thus, the invention makes it possible to completely eliminate or at any rate substantially reduce the air pollution produced in conjunction with heavily trafficked routes. The inven¬ tion thus affords a solution to the air pollution pro- blems, for instance in large or medium-size cities, with¬ out necessitating any expensive road constructions required when relocating through routes in urban areas. Another essential advantage of the invention is that traf¬ fic noise produced in connection with traffic routes can be minimised, whereby the environment in the vicinity of the traffic route can be considerably improved. Also the environment of the traffic route itself can be improved in that the roadways are always kept dry and thus are never slippery. This of course means improved road safety and travelling comfort.

It should finally be pointed out that it is known per se to arrange for ventilation in connection with roads or traffic routes passing through a tunnel. Gene¬ rally, this is done by providing fans sucking off air from the two opposite ends of the tunnel and discharging it through one or more shafts made in the rock at some point between the two tunnel ends. In that case, however, the air is not subjected to any filtering and thus is emitted into the ambient atmosphere in the uncleaned state. Thus, such ventilation of tunnels as suggested in the art - like the system disclosed in EP 0,237,625 - is no solution to the problems stated in the introduction to this specification. It would in fact be conceivable to solve these problems by placing, in accordance with the invention, a shell in existing tunnels and cleaning the air in the manner described above. Also, it should be pointed out that roads passing through tunnels are always constructed after the tunnel is finished, whereas the present invention is intended for use on existing roads or traffic routes, i.e. by applying a shell over the traffic route. It is obvious that the invention is not restricted to the embodiments described above and shown in the draw¬ ings. Thus, it is conceivable, for instance, to place the inventive shell over a traffic route having only one roadway or only a few roadways, in which case the outlets or exhaust air openings are arranged on one side of the shell. Furthermore, the treatment stations for cleaning the exhaust air can be modified in many different ways, both in respect of capacity and in respect of their geo¬ metrical configuration. When, in connection with the invention, it is said that the cleaned exhaust air from the interior of the shell is discharged into the atmos¬ phere, it should be understood that such discharge can be effected either directly from the respective treatment station, or indirectly through ducts from the station. Further, it should be emphasised that the treatment sta¬ tions need not necessarily work continuously during every hour of the day. Thus it is conceivable, in periods with a low degree of air pollution, to interrupt the operation of either all treatment stations or only some of them. Alternatively, in periods of low loads, the treatment stations can be operated at a reduced air flow capacity, thereby reducing the power consumption.

Claims

1. A method for air treatment in the area of a traf- fie route for motor vehicles emitting air-polluting exhaust gases, comprising the steps of first completely or partly encapsulating the traffic route in an elongate shell (1), and thereafter evacuating the air present in said shell and polluted by the exhaust gases from the vehicles (30) passing through the interior (10) of the shell, c h a r a c t e r i s e d in that the thus eva- . cuated exhaust air is caused to pass through filters (22, 22' ) in which it is cleaned before being discharged into the atmosphere. 2. Method as claimed in claim 1, c h a r a c t e r ¬ i s e d in that the polluted exhaust air is at least partially evacuated through outlets (19) located on a low level in the shell (1), i.e. close to the roadway/roadways (2,

2') of the traffic route, so as also to entrain heavy gases or constituents included in the exhaust air.

3. Method as claimed in claim 1 or 2, c h a r a c ¬ t e r i s e d in that comparatively clean outdoor air or fresh air is supplied into the interior of the shell through one or more inlets (25, 46) located on a low level in the shell for thinning the polluted air in the interior (10) of the shell, and that the exhaust air is evacuated through at least two different types of outlet (19, 20), viz. a first type (19) which is located on a low level in the shell for evacuating heavy gases or constituents in the air, such as C0₂, N0_χ, S0₂, and a second type (20) which is located on a high level in the shell for evacuating lighter gases or constituents.

4. Installation for air treatment in the area of a traffic route for motor vehicles emitting air-polluting exhaust gases, comprising an elongate shell (1) which completely or partly encapsulates the traffic route (2) and in which outlets (19) are provided for evacuating the air present in said shell and polluted by the exhaust gases from the vehicles passing through the interior (10) of the shell, c h a r a c t e r i s e d in that said outlets (19) communicate with filters (22, 22') for clean- ing the thus evacuated exhaust air before it is discharged into the atmosphere.

5. Installation as claimed in claim 4, c h a r a c ¬ t e r i s e d in that it comprises a plurality of air- treatment stations (11) spaced from each other in the longitudinal direction of said shell and each comprising at least one outlet (19) and a fan (23) cooperating there¬ with and serving to draw exhaust air from a point located on a low level in said shell, i.e. close to the roadway/ roadways (2', 2") of the traffic route, and a set of exchangeable filters (22, 22') mounted in a house (12), said outlet communicating with said house through a duct (17).

6. Installation as claimed in claim 4 or 5, c h a r a c t e r i s e d in that it comprises one or more inlets (25, 46) located on a low level in the shell for supplying comparatively clean outdoor air or fresh air into the interior of the shell, for thinning the polluted air therein, and at least two types of outlet (19, 20), viz. a first type (19) which is located on a low level in the shell for evacuating heavy gases or constituents in the air, such as C0₂, N0_χ, S0₂, and a second type (20) which is located on a high level in the shell for evacuat¬ ing lighter gases or constituents.

7. Installation as claimed in claim 5 or 6, c h a - r a c t e r i s e d in that the set of filters (22, 22' ) is arranged between said outlet (19) and said fan (23).

8. Installation as claimed in any one of claims 5-7, c h a r a c t e r i s e d in that the outlet (19) is located in the area between two parallel roadways (2' , 2" ) for traffic travelling in opposite directions.

9. Installation as claimed in any one of claims 4-8, c h a r a c t e r i s e d in that the house (12) accom¬ modating said set of filters (22, 22') is arranged in a roof (5) of said shell (1), and that inlets (25, 26) for supplying fresh air into the interior of said shell are arranged in walls (3, 4) of the shell.

10. Installation as claimed in any one of claims 5-9, c h a r a c t e r i s e d in that the distance between adjacent exhaust air treatment stations (11) is in the range of 50-200 m, suitably 75-100 m.

11. Installation as claimed in any one of claims 4-10, c h a r a c t e r i s e d in that the shell (1) comprises two separate, substantially vertical outer walls (3, 4) located on both sides of the roadway/roadways (2', 2"), and a roof (5) comprising two slanting roof panel units (6, 7) converging into a common ridge (8).

12. Installation as claimed in claims 8 and 11, c h a r a c t e r i s e d in that a partition (9) is arranged in the area between, for instance midway between said two outer walls (3, 4) of the shell, said partition separating said roadways (2' , 2") from each other and being provided at its lower end, at least in the area of an exhaust air treatment station (11), with said outlet (19).

13. Installation as claimed in any one of claims

4-12, c h a r a c t e r i s e d in the shell (1) is at least partly covered with one or more buildings (35, 35') such as dwelling houses and/or office buildings.

14. Installation as claimed in any one of claims 4-13, c h a r a c t e r i s e d in that the air treat¬ ment station (11') comprises a heat exchanger unit includ¬ ing two spaced-apart air passages or ducts (40, 42), of which a first (40) serves to supply the interior of a building with clean, tempered fresh air which is drawn in through and cleaned by one or more filters (41), while a second duct (42) communicates with the interior of the road-encapsulating shell (1) and serves to conduct the comparatively warm exhaust air therefrom past one or more casings (44) which enclose said filters (41) and through which heat transfer can be effected without the air cur¬ rents in the respective ducts contacting one another.

15. Installation as claimed in claim 14, c h a r ¬ a c t e r i s e d in that in front or upstream of said casings (44) there are arranged one or more filters (41') serving to clean the exhaust air from the interior of the shell (1) before it reaches said casings (44).

16. Installation as claimed in claim 13 and claim 14 or 15, c h a r a c t e r i s e d in that the heat exchanger unit (41, 44) is included in or adapted to serve at least one of the buildings (35, 35') covering the shell

(1).