CA2106582C - Element for sealing and monitoring a body, in particular a refuse dump - Google Patents

Abstract

The invention relates to an element for sealing and monitoring a body (1). Provision is made for two seals (4, 5) to be spaced apart by supporting elements (6), while at least one channel (7) remains free between the supporting elements 16). At the outlet openings of said channel one or more sensors (18) is or are disposed.
The seals (4, 5) are connected to each other at their edges. The supporting elements (6) consist of a material which is permeable but resistant to flow, preferably a material whose flow resistance perpendicular to the channel (7) is less than that parallel to the channel (7). The position of a leak (29) can be determined with the aid of two sensors (18), which in a refuse dump also determine whether the leak (29) is located in the lower or upper seal (4, 5).

Description

- FILE, ~N 11~ THIS AM~NDED ,~ 1 0 ~ 5 ~ TRANSLATION ~ ~ 2 Element for sealing and monitoring a body, in particular a refuse dump The invention relates to an element for sealing and monitoring a body having two seals, which at their edges are sealingly connected together, leaving free an inlet opening and an outlet opening for a medium, while at least one sensor can be connected to the outlet opening.
From DE 37 37 569 Al a device for the base sealing of deposits is known. Two seals extending over a large area are here sealingly connected together at their edges, leaving free an inlet opening and an outlet opening for a medium. The medium, which may be air, flows through the space between. The medium passes through the outlet opening to a sensor, in which a substance penetrating can be identified by gas-chromatography. With this device it can be determined whether a substance has penetrated into the cavity through a leak in one of the two seals. However, the leak cannot be located.
From BMT, volume 34, No. 4, April 1987, Pages 196 to 200, a simple seal consisting only of a sheet is known. A device for locating leaks is associated with this sheet. Since the leak locating device is situated in a filter layer, which usually consists of sand and has no homogeneous flow resistance, after a leak has occurred in the sheet a substance passing through the leak can travel through the filter layer until it is detected at an undetermined point. The known arrangement is not a handy element consisting of two seals, which has a reliable sealing action and would be easy to lay. On the contrary, it is a simple association of a sheet and a locating system.
A similar device to that from BMT, Volume 34, No.
4, April 1987, Pages 196 to 200, can also be seen in the Siemens leaflet "long-term refuse dump monitoring with LEOS", Order No. A 19100-U653-A222, July 1990. From this leaflet a device for sealing a refuse dump and for detecting and locating leaks is known. This provides for REPLACEMENT SHEET

~106~i82 WO 92/16316 - la - PCT/DE92/00236 the refuse dump to be equipped with a waterproof sheet, sealing sheeting (particularly of plastic material) or "seal". This seal may be disposed under the refuse body (base seal), so that no noxious matter can pass into the groundwater. The seal may however also be placed above the refuse body (surface seal), in order to prevent the penetration of rainwater and therefore to prevent noxious matter from being washed out of the refuse. In order to detect in good time a leak (damage) in this seal, provision is made with the known device to lay so-called LEOS hoses on the side of the seal remote from the refuse body. The LEOS hoses, which are laid in a meander pattern and are filled with air, and whose wall is permeable to various substances present in the refuse, are connected to a central monitoring system. In the case of a seal situated under the refuse body, a damaged point in the seal is located by detection of substances dissolved in the leakage water, while when the seal is placed above the refuse body, damage in it is located by detecting rising fermentation gases.
A LEOS hose and a device serving to operate it are known from German Patent Specification 24 31 907.
This relates to a hose which is permeable to noxious substances. At one end of the hose a pump is disposed, with which individual volumes of a medium, for example individual gas volumes, can be delivered one after the other through the hose at intervals of time. The hose is in this way flushed for some time at regular intervals of REPLACEMENT SHEET

2~0~582 time, that is to say with a constant flushing frequency.
Sensors sensitive to noxious substances are disposed at the other end of the hose. If a noxious substance comes into the vicinity of the hose, it will penetrate into the latter and be brought to the sensors by the next medium pumping operation. Since during this operation the medium flows at a known speed, the difference between the moment of time when the pump is switched on and the moment of time when the sensors react will make it possible to determine accurately the point where a noxious substance entered the hose between two flushings. In addition, the amount of noxious substance can be determined.
If a leak in the seal does not occur in the direct vicinity of the LEOS hose, the substance to be detected which has escaped is distributed over a larger area before it reaches the LEOS hose. In the event of different speeds of propagation in this area the substance may reach the LEOS hose simultaneously at more than one point. The substance to be detected may also reach the LEOS hose only at a point relatively distant from the leak. Moreover, between two flushings the substance may reach and diffuse into a relatively large portion of the hose. It will then only be possible to determine that the leak is situated somewhere in the region of that portion of the hose.
Determination of the location of the leak may consequently be subject to relatively considerable error. With the known device a leak in the seal cannot always be accurately located. Furthermore, the laying of the seal and that of the LEOS hoses constitute two operations.
The invention is based on the realization that it is appropriate to provide increased protection by means of a double barrier. This would be expedient both for the base seal and for the surface seal of a refuse dump. It is in addition based on the reflection that it is then also appropriate to provide a configuration such that it can be determined by measurement techniques whether one barrier or the other has a leak and where this leak is situated.
REPLACEMENT SHEET

~ 3 ~ 2 1 0 65 82 The problem underlylng the lnventlon ls that of lndlcatlng an element for seallng and monltorlng a body, wlth whlch the slte of a leak can be very accurately located and wlth whlch double leak protectlon ls ensured by the use of two barrlers. The element should be able to be lald qulckly and rellably.
Accordlng to the lnventlon there ls provlded element (2) for seallng and monltorlng a body (1), whlch element (2) comprlses two seals (4, 5) havlng edges, whlch two seals (4, 5) are seallngly connected together leavlng free an lnlet openlng and an outlet openlng for a medlum, whlle at least one sensor (18) can be connected to the outlet openlng, characterlzed ln that the two seals (4, 5) are spaced apart by supportlng elements (6), ln that between the seals (4, 5) and the supportlng elements (6) at least one channel (7) ls formed whlch connects together the lnlet openlng and the outlet openlng, and ln that the supportlng elements (6) are made of a materlal permeable but reslstant to flow for a substance to be detected, and havlng a known flow reslstance.
Wlth thls element the advantage ls achleved that after a leak has occurred ln one of the seals a substance to be detected ls passed to the channel ln a deflned manner. The substance does not flow through an envlronment whose structure ls unknown, but proceeds through the supportlng elements to the channel. The flow reslstance of the supportlng elements or of the cavltles ln the supportlng elements ls known and, at least ln the dlrectlon of each axis of the supportlng element, - 3a - 21 06582 is constant. The substance penetratlng flrst passes from the leak ln the seal lnto the channel by the shortest route, namely at rlght angles to the channel. Only then does the penetratlng substance arrlve at the channel at nelghborlng polnts. In the perlod of tlme between the occurrence of the leak and the next flushlng a substance dlstributlon ls formed ln the channel wlth a maxlmum whlch durlng flushlng and detectlon lndlcates the slte of the leak. Wlth a low flow reslstance of the supportlng element the dlfferences in tlme between arrlval via the direct route and arrlval vla the rather longer routes are very sllght. In the perlod of tlme between the occurrence of the leak and the next flushlng a wlde, flat ~L

~ 2106582 distribution of substance could then build up in the channel, with an undetectable maximum. However, owing to the fact that according to the invention the supporting elements are made of a material resistant to flow, the penetrating substance moves so slowly in a supporting element that the difference in time between arrival at different points in the channel is measurably large even when the difference between the paths followed is slight.
In the period of time between the occurrence of the leak and the next flushing, with a predetermined flushing frequency in the channel only a narrow, steep substance distribution can be formed, the maximum of which can be well recognized by the sensor. Consequently, it can easily be determined where the substance first reached the channel. The leak must then lie on a line at right angles to this point on the channel.
Only one sensor may be provided for a determined substance, or a plurality of sensors for different substances may be provided.
With the element according to the invention good location of a leak in the seal is possible.
Through the fixed connection between the seals and the channels the element according to the invention can be laid quickly in a single operation.
If different substances are to be expected below and above a laid element, the type of substance detected will make it possible to deduce whether the leak is in the top or the bottom seal. The nature of the substance can be detected by providing appropriate sensors. For example, an element according to the invention may seal a refuse dump. The penetration of almost pure water would then permit the assumption of a leak in the top seal facing away from the refuse dump body.
The channel may for example be in the form of a permeable hose. The hose known from German Patent Specification 24 31 907 may be suitable.
According to another example of embodiment the channel in the element may be separated from neighboring supporting elements by permeable diffusion layers. No - ?lOfi582 hose is then necessary.
The hose may be surrounded by a filling material.
A drying agent may be used as filling material, or as a component of the supporting elements, in order to eliminate residual moisture in the element. The accuracy of measurement of moisture penetrating through a leak can thus be improved. A moisture sensor is for example used to determine the penetration of water.
According to a further development the supporting elements have lower flow resistance at right angles to the channel than parallel to the channel. The advantage is thereby gained that the substance penetrating into the supporting element through a leak in a seal will spread out in the shape of an ellipse and not circularly. The longer axis of the ellipse is then directed at right angles to the channel. A still narrower, steeper substance distribution is consequently obtained in the channel than when use is made of a homogeneous flow-resistant material as supporting element, that is to say a material permitting the same speed of flow in all directions. The leak can thus also be located with greater accuracy.
The material of the supporting elements, which has lower flow resistance at right angles to the channel than parallel to the channel, may for example be a woven fabric directed at right angles to the channel. The material of the supporting elements may however also be constructed of capillaries, tubules or the like, directed at right angles to the channel.
The two seals may be sealingly connected together at their edges at the channel ends, but also in places where there are no channel ends, by means of sectional members fitted onto them. Such sectional members are easy to handle. The two seals may however also be welded together.
The inlet and outlet for the medium flowing through the channel may be connected together to form a circuit. The sensor and a pump are then disposed in the circuit. As long as no leaks occur, the medium flowing - 210~82 through the channel need not be continually replenished.
The circuit has for example a closable feed opening and a closable outlet opening. Between the outlet opening and the feed opening the circuit should be completely or partially closable. Medium can then be introduced and drawn off as required. The circuit can be interrupted, so that all the medium introduced can be drawn off again. Instead, with a partially closed connection between the outlet opening and the feed opening, only a part of the medium in the circuit may be replaced.
In the outlet or in a bypass around the outlet a filter is for example disposed, which can remove substances penetrating into the circuit through a leak.
A filter of this kind may be a catalytic filter.
Particularly when the filter is disposed in a bypass around the outlet, it can be replaced or cleaned without impairing the intactness of the circuit. In certain circumstances it is appropriate to measure the substances removed from the filter in the cleaning operation. For this purpose the filter may be connected to a cleaning device and to a sensor in order to permit sensitive, integral measurement.
In addition to immediate determination of penetrating noxious substances by means of the sensor, it is also possible to determine in the manner described, the penetration of noxious substances between two filter changes. In the event of the failure of the sensor, it can thus at least be ascertained whether a leak existed between two filter changes.
For the purpose of cleaning the filter to remove retained substances, the filter may be provided with a heating system. This heating system serves the purpose of freeing the retained substances by heating. The filter may also be able to be charged with water vapor or water.
By this means also the substances retained in the filter can be freed again.
A plurality of the elements described for sealing and monitoring a body can preferably be sealingly 2106~82 connected together to form a panel. In this case the outlet opening of the channel of the one element is connected to the inlet opening of the channel of another element. With an arrangement of this kind the advantage is gained that for the purpose of sealing a large area, for example a refuse dump, it is not necessary to provide a large one-piece cover element which would be difficult to transport and to handle. The advantage is gained that with simple means it is possible to form quickly, from handy individual elements, a panel which can take over the duty of a very large element for sealing and monitoring a body.
The adjoining elements may for example be welded together to form a panel. They may however also be joined in other ways. For example, a sectional member, which is disposed on the edge of one element and which holds the two seals of that element, may also be provided with devices for holding the seals of the adjoining element.
Only one sealing sectional member is thus then situated between two adjoining elements. In order to ensure a particularly leakproof connection, a weld seam may nevertheless be necessary.
The channels of adjoining elements may for example be joined together by means of plug-in connections. However, other forms of connection, for example welded joints, are also possible.
The individual elements can be joined together to form a panel in such a manner than only one channel passes through the entire panel, covering the whole panel in a meander pattern. The entire panel then has only one feed inlet and only one outlet and needs, for all the elements, only one common sensor, which may also be in the form of a double sensor, for example for water and methane gas.
With an element according to the invention the advantage is achieved that a leak in one of its seals can be detected and accurately located. In addition, kncwing which substance has penetrated makes it possible to ascertain whether the substance detected comes from the ~lQ6582 interior of the space monitored or comes from outside.
For this purpose sensors responding to different substances or a plurality of sensors for different substances, for example for noxious substances or gases such as methane gas and for water, are necessary.
Examples of embodiment of the invention will be explained more fully with reference to the drawing, in which:
Figure 1 shows a refuse dump sealed at top and bottom, for which respective flexible panels composed of sealing and monitoring elements are used;
Figure 2 is a section through an element according to the invention;
Figure 3 shows another embodiment of an element according to the invention;
Figure 4 shows a device with a channel lead-through for connecting together two elements, the drawing being turned by 90~ relative to Figure 2;
Figure 5 shows a connection, without a channel lead through, between two adjoining elements;
Figure 6 shows a panel comprising a plurality of elements, with an appertaining installation for its operation, and Figure 7 shows the flow pattern starting from a leak in an element.
According to Figure 1, a refuse dump comprising a refuse body 1 is sealed at the top and at the bottom by a device having a configuration according to the invention. This device comprises a top panel Fl and a bottom panel F2, each panel consisting of monitorable double seals, which hereinbelow will be referred to as ~elements" 2. These elements 2, each of which has two parallel longitudinal channels 7, are connected together at respective joints 50. By means of the upper panel F1 the penetration of water from above into the refuse body 1 and the escape of refuse gas in the upward direction from the refuse body 1 are monitored, and a corresponding leak is located. By means of the bottom panel F2 the escape of refuse gas from the refuse body 1 in the 21Qfi582 g downward direction and the penetration of moisture from below upwards into the refuse body 1 are monitored, and a corresponding leak is indicated. Each panel F1, F2 comprises two barriers for gas and moisture, as will become clear later on. The monitorable upper panel F1 is covered with earth and the monitorable panel F2 rests on a mineralogical sealing layer.
According to Figure 2 an element 2 consists of a bottom seal 4 and a top seal 5. The two impermeable sheets, sealing sheetings, coverings or seals 4 and 5, which for example consist of polyethylene or other plastic material, are spaced apart by supporting elements 6. Between the seals 4 and 5 and the supporting elements 6 a channel 7 is left free, which extends through the element 2 at right angles to the plane of the drawing.
Two (see Figure 1) or more channels 7 could also be provided in each element. Except for the inlet opening and the outlet opening of the channel 7, the element 2 is sealingly closed on all sides at its edges, the top seal 5 being for example welded to the bottom seal 4. The weld joint is designated 45. In Figure 2 a permeable hose 8 is laid in the channel 7 and corresponds to the hollow duct according to German Patent Specification 24 31 907. It consists in particular of a LEOS hose. It can effectively convey gas and water vapor over great lengths. The hose 8 is surrounded by a filling material 8a, for example sand or a drying agent.
The supporting elements 6 consist of a material permeable but resistant to flow. By this is meant a material which leads to not too rapid but also not too slow spreading-out of water vapor and/or refuse gas. The supporting elements 6 may also consist of a material which has a lower flow resistance at right angles to the channel 7 than parallel to the channel 7. Such a material may be an aligned woven fabric. The material may also consist of capillaries or tubules extending parallel and aligned at right angles to the channel 7. It may for example be made of polyethylene or other plastic material. The filling material 8a is a material which ~Ofi58~

retains moisture. The filling material 8a is however not completely indispensable.
The width b of the elements 2 according to Figure 2 may for example amount to from three to five meters.
Its length may for example amount to 50 meters. Such sheets are flexible and relatively simple to lay and then to join to one another.
According to Figure 3 it is also possible to dispense with the hose in the channel 7. The channel 7 is then separated from the adjoining supporting elements 6 by permeable diffusion layers or diffusion walls 9. The channel 7 then corresponds to the hollow ducts according to German Patent Specification 24 31 907. In principle the walls 9 can also be dispensed with.
According to Figure 4 the two seals 4 and 5 of a first element 2A are connected together at their right-hand edge by a sectional member 10 having a central opening and fitted onto said seals. The sectional member 10 serves at the same time to hold the seals 4 and 5 of an adjoining identical second element 2B. The sectional member 10 thus joins together the left-hand edges of the seals 4 and 5. The elements 2A, 2B are thus also joined together at the joint 40. In this way a plurality of elements 2 can be joined together in modular fashion to form an array or a panel. For the purpose of connecting the channels 7 or hoses 8 of the two elements 2A and 2B
which are to be joined together, the sectional member 10 has a through opening 11. A rigid sleeve 12 is disposed therein. Said sleeve is welded fast in the through opening 11. The hoses 8 can be connected on both sides to the sleeve 12, for example by means of clips 13. In this way the outlet opening 8A of the channel 7 of the left-hand element 2A is connected to the inlet opening 8B of the channel 7 of the right-hand element 2B. A medium, such as air, for example, can now flow from left to right, as indicated by arrows, through intermittent suction or pressure action. In the structure shown in Figure 4 weld seams 14 are necessary for sealing purposes at top and bottom.

~10678~

Where no connection is necessary between adjoining channels 7, adjoining elements 2 can be coupled or connected together at a joint 50 also by means of a simple weld seam 52, as shown in Figure 5. Figure 5 thus shows such a weld joint between adjoining elements 2A, 2B
outside a channel leadthrough. Instead of a weld seam 52 directly at the connection of the seals 4 and 5, the joint 50 may also consist of a cover plate 54 which is sealingly welded at the ends of the two adjoining elements 2A and 2B. The weld seams necessary for this purpose are designated 56. Instead of this, however, a sectional member 10 not provided with a through opening 11 may also be used (not illustrated).
According to Figure 6 an arrangement may be selected in which the elements 2 are joined together to form a panel F. The channels 7 are passed through the panel F in a meander pattern. For this purpose U-shaped connectors 16 are required for the rows of elements 2A, 2B. In principle, the channels 7 may also be disposed in a meander pattern in each element 2A, 2B. The channels 7 are components of a circuit for a suitable medium, which for example is dry air. A pump 17 and one or more detectors or sensors 18 for substances to be detected are arranged in the circuit. In the case of a plurality of sensors 18, these respond to different substances. Two sensors 18, which are for example connected in series, are preferably provided, as illustrated. One sensor 18 responds to gas (refuse gas, particularly methane gas), and the other sensor 18 detects moisture (water). In addition, a pressure gauge 19, a flow meter 20, a safety valve 21 and also a pressurizer 22 may be provided.
In the circuit the medium is passed through the elements 2A, 2B at regular intervals (intermittent operation), as is known from German Patent Specification 24 31 907. For this purpose pumping is continued for some time and then a waiting period follows until any material has accumulated through diffusion in the channel 7 of a defective element 2A, 2B. In the event of a leak in one of the elements 2A, 2B the penetrating substance is ?1 Qfi~82 detected in the double sensor 18 in the next pumping phase. The circuit has, for example, an inlet 23 for air and an outlet 24 for air, which are provided with valves 23a and 23b respectively. Between the inlet 23 and the outlet 24 the circuit can be partly or completely closed by means of another valve 25. A closed circuit, a partly open circuit or an open circuit are thus available at choice. The pump 17, instead of being a pressure pump downstream of the inlet 33, may also be disposed as a suction pump 17a upstream of the outlet 34. A filter 26 is disposed in a bypass in order to clean the medium in the circuit. The filter 26 may be a mechanical filter, a filter having an absorptive action (molecular sieve, carbon filter, silica gel, etc.) or a filter working with catalytic combustion. For cleaning purposes this filter 26 can be disconnected from the circuit by means of fittings 26a, 26b, 26c. A heating means 27 is provided for the filter 26 for cleaning purposes. The substances removed are taken off via a flushing line 28 or fed to other sensors for integral measurement. The flushing line 28 may also be fed with hot water or steam in order to drive off the substances which are to be detected.
Since the medium is passed through the circuit at fixed intervals of time (flushings), the moment of time when a substance is detected in the sensor 18 will enable the site of the leak in one of the elements 2A, 2B to be deduced. In the case of a leak in a seal 4 or 5 of the element 2A or B, the penetrating substance will after a certain period of time pass into the channel 7 and will be conveyed from the latter with the medium to the sensor 18. In addition, when two sensors 18 are used it can be determined whether the top seal 4 or the bottom seal 5 of an element 2 is defective. From the nature of the substance penetrating (for example gas or water) it can be determined whether this substance comes from above or from below.
Figure 7 shows that because of the supporting elements 6, which are made of material resistant to flcw, the penetrating substance spreads out from a leak 29 ~ t O fi ~ ~ 2 slowly in the form of a circle (see circle a) and uniformly. It is thereby ensured that the substance which penetrated at the leak 29 first reaches the channel 7 via the shortest route, that is to say at right angles to the channel 7. In addition, it is ensured that between the appearance of the leak and the next flushing of the channel 7 only a small portion of the channel will receive the substance. Directly before the next flushing a distribution 30 of the substance as as [sic] shown in Figure 7 will be obtained in the channel 7. K is here the concentration of the substance in the channel 7, and z is the place in the channel 7. This distribution K(z) passes to the single or double sensor 18 (Figure 6), in which, with a relatively wide distribution 30, the maximum and hence the location of the leak can be determined only relatively accurately. The accuracy can be improved if the material of the supporting elements 6 has a lower resistance to flow at right angles to the channel 7 than parallel to channel 7. The substance penetrating through the leak 29 will in fact then spread out in the form of an ellipse (see ellipse b), the longer axis of which lies at right angles to the channel 7. It follows therefrom that in the space of time between the occurrence of the leak and the next flushing of the channel 7 the substance reaches and acts on only a relatively small portion of the channel 7. Directly before the next flushing a distribution 31 having a sharp maximum is obtained in the channel 7. This maximum can be more accurately determined in the sensor 18 (Figure 6). The location of the leak can be determined with equal accuracy.
With an element 2 according to the invention a leak (or a plurality of leaks) in a seal 4, 5 can be located very accurately. Depending on the composition of the penetrating medium, it can also be distinguished whether the leak has occurred in the top seal 5 or in the bottom seal 4. The point in the channel 7 lying closest to the leak 29 can be determined.

Claims (23)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Element (2) for sealing and monitoring a body (1), which element (2) comprises two seals (4, 5) having edges, which two seals (4, 5) are sealingly connected together leaving free an inlet opening and an outlet opening for a medium, while at least one sensor (18) can be connected to the outlet opening, characterized in that the two seals (4, 5) are spaced apart by supporting elements (6), in that between the seals (4, 5) and the supporting elements (6) at least one channel (7) is formed which connects together the inlet opening and the outlet opening, and in that the supporting elements (6) are made of a material permeable but resistant to flow for a substance to be detected, and having a known flow resistance.

2. The element (2) as claimed in claim 1, characterized in that the channel (7) is separated from the adjoining supporting elements (6) by permeable diffusion layers (9).

3. The element (2) as claimed in claim 1, characterized in that the channel (7) is formed by a permeable hose (8) or contains such a hose (8).

4. The element (2) as claimed in claim 1, characterized in that the channel (7) contains a permeable hose (8).

5. The element (2) as claimed in claim 3 or 4, characterized in that the hose (8) is surrounded by a filling material (8a).

6. The element (2) as claimed in one of claims 1, 2, 3, 4 or 5, characterized in that the supporting elements (6) have a lower flow resistance at right angles to the channel (7) than parallel to the channel (7).

7. The element (2) as claimed in claim 6, characterized in that the material of the supporting elements (6) is a woven fabric directed at right angles to the channel (7).

8. The element (2) as claimed in claim 6, characterized in that the material of the supporting elements (6) is constructed from capillaries or tubules directed at right angles to the channel (7).

9. The element (2) as claimed in one of claims 1, 2, 3, 4, 5, 6 or 7, characterized in that the two seals (4, 5) are connected together at the edge by a sectional member (10).

10. The element (2) as claimed in one of claims 1, 2, 3, 4, 5, 6, 7, 8 or 9, characterized in that the inlet opening and outlet openings for the medium are connected together to form a circuit, and in that the sensor (18) and a pump (17, 17a) are disposed in the circuit.

11. The element (2) as claimed in claim 10, characterized in that the circuit has a closable inlet (23) and a closable outlet (24), and in that the circuit can be completely or partly closed between the inlet (23) and the outlet (24).

12. The element (2) as claimed in one of claims 1 to 10, characterized in that a filter (26) for receiving noxious substances is disposed in a line (33, 34) connected to the inlet or outlet opening or in a bypass in said line (33, 34).

13. The element (2) as claimed in claim 12, characterized in that the filter (26) is a catalytic filter.

14. The element (2) as claimed in one of claims 12 or 13, characterized in that the filter (26) can be disconnected from the line (33, 34) and preferably connected to a cleaning device and to a sensor for measuring the substances removed by the cleaning.

15. The element (2) as claimed in claim 12, 13 or 14, characterized in that the filter (26) is provided with a heating means (27).

16. The element (2) as claimed in one of claims 12, 13, 14 or 15, characterized in that the filter (26) can be charged with water vapor or water.

17. The element (2) as claimed in one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16, characterized in that two sensors (18) are provided, of which one sensor (18) reacts to gas and the other to moisture.

18. The element (2) as claimed in one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17, characterized in that it is sealingly connected to at least one other element (2) to form a panel (F1, F2; F).

19. The element (2) as claimed in claim 18, characterized in that the outlet opening of the channel (7) of the element (2) is connected to the inlet opening of the channel (7) of the at least one other element (2).

20. The element (2) as claimed in claim 18 or 19, characterized in that adjoining elements (2) are welded together at weld joints (14, 52, 56).

21. The element (2) as claimed in one of claims 18 or 19, characterized in that the channels (7) of adjoining elements (2) are connected together by plug-in connections.

22. The element (2) according to one of claims 18, 19, 20 or 21, characterized in that the channels (7) are arranged in a meander pattern in the panel (F1, F2; F).

23. The element (2) as claimed in one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22, characterized in that a pump (17, 17a) which acts intermittently is connected to the inlet or outlet opening, so that in the intervals between pumping periods substance can penetrate from the environment into the channel (7).