The present invention relates to a wall feedthrough fitting monitoring device. The present invention further relates to a sensor foil for a wall feedthrough fitting monitoring device, a fire-resistance and/or flame-retardance monitoring system, a use thereof and a method for monitoring the fire-resistance and/or flame-retardance of a building.

Wall feedthroughs are commonly used in building, and in particular in publicly accessible building. Such feedthroughs are generally used to lead pipes or cables through a wall, floor or ceiling in a building from one room to another. In view of fire-resistance and/or flame-retardance, it is desired to separate individual rooms in a building as much as possible. Wall feedthroughs do interconnect rooms and are thus undesirable from a fire- resistance and/or flame-retardance point-of-view.

To improve the fire-resistance and/or flame-retardance of the feedthroughs, fire- resistant and/or flame-retardant wall feedthrough fittings are known, which close-off the feedthrough when a fire would occur. For example, such fittings comprise a fire-resistant and/or flame-retardant foam that expands when heated, such that the flames are prevented from passing through the feedthrough.

To safeguard the working of the wall feedthrough fitting, it must remain intact after installation, since damaging of the fitting would cause it to no longer work. Accordingly, the conditions of the wall feedthrough fitting need to be monitored often, in order to be sure that it integrity remains safeguarded and that it remains in working order. Hence, when a new cable or pipe needs to be guided through the wall, one may normally be tempted to do this next to an existing cable or pipe.

Presently this monitoring is done by vision of an auditor in a periodic manner. However, such monitoring is labour-intensive and the periodic nature implies that a damaged wall feedthrough fitting remains unobserved for a certain period of time, namely until the next inspection.

It is therefore an object of the present invention to provide a way of monitoring a fire- resistant and/or flame-retardant wall feedthrough fitting in a way that does not have the drawbacks of the known monitoring, or at least in an alternative way. The present invention thereto provides a wall feedthrough fitting monitoring device for monitoring the integrity of a fire-resistant and/or flame-retardant wall feedthrough fitting, comprising: at least one sensor, which is configured to be mounted over a fire-resistant and/or flame-retardant wall feedthrough fitting, such that the integrity of the at least one sensor is representative for the integrity of the fire-resistant and/or flame-retardant wall feedthrough fitting, and a transmitter device, which is connected to the at least one sensor and which is configured to transmit a sensor signal that is representative for the integrity of the sensor.

The wall feedthrough fitting monitoring device is configured to monitor the integrity of the fire-resistant and/or flame-retardant wall feedthrough fitting in an automated manner. As such, it is no longer required to carry out manual inspections by an auditor in a periodic manner, but the monitoring may rather be carried out continuously and autonomously. The monitoring is thus less labour intensive and can be carried out more often, which enhances the certainty with which the fire-resistance and/or flame-retardance of the building can be assured.

The integrity of the fire-resistant and/or flame-retardant wall feedthrough fitting, e.g. in an intact and non-damaged condition, may be defined as a state in which the fitting is still operable to prevent the passage of flames and to work properly within the respective safety standards. As such, minor damages of the fitting may be acceptable and do not need to be detected. However, the monitoring device may be able to detect more severe damaging of the fitting that would cause the fitting to no longer work properly. An example of such severe damaging could be a through hole in the wall, adjacent to the existing wall feedthrough fitting, to allow for passage of another cable, pipe or the like.

The monitoring device comprises at least one sensor that is configured to be mounted at the respective wall in which the wall feedthrough fitting is provided. With the term wall, not only walls are meant, but also ceilings, floors or other building elements that may be equipped with fire-resistant and/or flame-retardant wall feedthrough fittings.

The at least one sensor will be mounted such, that it at least partially covers an area of the respective wall, behind/underneath which the fitting is provided. The at least one sensor may thereto be provided at one side of the wall, which is a particularly suitable location to detect newly-applied through holes in the wall. In case it is also desired to detect minor damages of the fitting, a sensor may need to be applied at both sides of the wall, in order to detect damages at both sides.

The at least one sensor is electrically connected to a transmitter device of the monitoring device, e.g. in a manner that allows transmission of a signal from the sensor towards the transmitter device. The transmitter device may as well be connected to more than a single sensor, for example to two sensors for the same fitting, but on opposite sides of the wall.

The transmitter device is configured to transmit a signal that is representative for the integrity of the sensor, and thus for the integrity of the respective wall feedthrough fitting on which the sensor is mounted. Hence, damaging of the wall feedthrough fitting from the outside would also cause damaging of the sensor that is mounted on top of the wall, e.g. over the fitting.

In an embodiment, the transmitter device is configured to transmit a reference sensor signal when the sensor is intact and configured to transmit a different sensor signal, not being the reference sensor signal, when the sensor is damaged. During normal operative conditions of the wall feedthrough fitting, the transmitted sensor signal thus remains substantially constant, e.g. at the reference sensor signal. An operator of the monitoring device can assure himself of proper functioning of the wall feedthrough fitting when the sensor signal is equal to the reference sensor signal. However, when the sensor signal is no longer the same as the reference sensor signal, the wall feedthrough fitting may be damaged and may need repair to function properly again.

In an embodiment, the at least one sensor comprises an electrode that is configured to be mounted on the wall and over the respective wall feedthrough fitting. This electrode is electrically connected to the transmitter device and has an electrical resistance.

This electrical resistance is a measure for the integrity of the sensor and thus also for the wall feedthrough fitting onto which the sensor is mounted. In particular, the intact sensor, e.g. the non-damaged sensor, may have a certain electrical resistance that can be measured by the transmitter device. On the basis of the electrical resistance of this intact sensor, the transmitter device can be set to transmit the reference sensor signal. Accordingly, one can be assured that the wall feedthrough fitting is intact as long as the transmitted sensor signal is equal to the reference sensor signal.

As soon as the sensor is damaged, the electrical resistance of the sensor will change. Accordingly, the sensor signal transmitted by the transmitter device may also change and will then no longer be the same as the reference sensor signal, since the sensor is no longer intact. This difference in sensor signal may be notified, indicating the damaging of the wall feedthrough fitting.

Such a notification may be sent automatically and requires no human input.

Accordingly, the integrity of the fire-resistant and/or flame-retardant wall feedthrough fitting may be monitored in real-time, either continuous or intermittently at certain predefined intervals, without requiring constant human monitoring. In an embodiment of the monitoring device, the sensor comprises a first electrode and a second electrode. The transmitter device may be connected to both of the electrodes and is configured to compute the electrical resistance between the first electrode and the second electrode. The transmitter device is further configured to transmit the sensor signal on the basis of the computed electrical resistance.

The electrical resistance may thereby depend on the overall electrical resistance of an electronic circuit from the transmitter device towards the first electrode, the second electrode and back towards the transmitter device. Upon damaging of the sensor, the electronic circuit may be broken in its entirety, giving rise to an infinitely high electric resistance and thus to a sensor signal that is no longer the same as the reference sensor signal.

However, the electric resistance of the sensor may also depend on a distance between the first electrode and the second electrode and/or on the electric resistivity of a material in between the first electrode and the second electrode. Upon damaging of the sensor, the distance between the first electrode and the second electrode may change, and may for example increase, which would give rise to an increase in electric resistance and therefor to a sensor signal that is no longer the same as the reference sensor signal either.

In a further embodiment, the sensor is a sensor foil, which is adapted to be mounted at least partially over the wall feedthrough fitting. Such a sensor foil may be a thin, flexible and generally flat foil, which can be plied to accommodate for the surface on which it is mounted, e.g. the surface of the wall in which the wall feedthrough fitting is located. The advantage of such a foil is that it can be applied on a wider range of surfaces, even rough or non-flat surfaces, while still forming a sufficiently accurate sensor for monitoring the integrity of the wall feedthrough fitting.

The sensor foil comprises a first conductive layer that forms the first electrode, a second conductive layer that forms the second electrode, and an electrical insulator layer. The foil thereby mainly extends in a plane, for example a flat plane, and is built out of the conductive layers and the insulator layer.

According to this embodiment, the first conductive layer is spaced from the second conductive layer and the electrical insulator layer is arranged in between the first conductive layer and the second conductive layer, thereby separating the first electrode and the second electrode from each other.

The electrical insulator layer in between the first conductive layer and the second conductive layer has a certain electrical resistance for the intact condition of the sensor foil. This electrical resistance of the insulator foil may be relatively large, especially when compared to the electrical resistance of the first conductive layer and the second conductive layer themselves. As such, the overall electrical resistance of the electronic circuit may be mostly determined by the insulator layer.

When the sensor foil were to be damaged, the insulator layer may be influenced, for example being reduced in thickness, compared to when the sensor foil were intact. This damaging thereby results in a reduced electric resistance of the sensor foil, which would result in sensor signal from the transmitter device that is no longer the same as the reference sensor signal.

Furthermore, the first electrode, e.g. the first conductive layer, and the second electrode, e.g. the second conductive layer, may be short-circuited when the sensor foil were to be damaged. For example, when the sensor foil were to be punctured by a metallic drill, for drilling a hole through the wall, the drill both protrudes the first conductive layer and the second conductive layer, thereby short-circuiting both. Accordingly, the drop in electrical resistance will result in a different sensor signal being transmitted by the transmitter device, no longer being the same as the reference sensor signal.

In a further embodiment, the first conductive layer is electrically connected to the transmitter device via a first terminal of the sensor foil and the second conductive layer is electrically connected to the transmitter device via a second terminal of the sensor foil. The transmitter device is thereby configured to compute the electrical resistance between the first terminal and the second terminal and is further configured to transmit the sensor signal on the basis of the computed electrical resistance.

By computing the electrical resistance over both terminals, the overall electrical resistance over both conductive layers and the insulator layer can be established by the transmitter device. On the basis of the computed electrical resistance, the transmitter device may transmit the reference sensor signal, when the sensor foil is intact, or may transmit a different sensor signal, when the sensor foil is damaged.

In an alternative or additional embodiment, the first conductive layer is printed onto a first surface of the insulator layer and the second conductive layer is printed onto an opposed second surface of the insulator layer.

During manufacturing of the sensor foil, the insulator layer is thereby provided first. The first conductive layer is thereafter printed at one side of the insulator layer, on the first surface thereof, and the second conductive layer is thereafter printed at another side of the insulator layer, on the second surface. The printing of the conductive layers may involve the deposition of a flat and even layer of electrically conductive material on both sides of the insulator layer, but may also involve printing of electrically conductive material in a certain conductor pattern such as in a grid pattern or a line pattern. The benefit of printing in such patterns may be that less conductive material needs to be used, when compared to a flat and even layer, but that the respective conductive layers may still have sufficient coverage across the insulator layer to ensure proper functioning of the sensor foil.

In an alternative embodiment, the sensor foil comprises a plurality of wires that extend parallel to each other in a planar direction of the sensor foil. The wires are, at one end, all electrically connected to a first terminal of the sensor foil and are all electrically connected to a second terminal of the sensor foil at their opposing ends.

In an intact condition of the sensor foil, all wires extend between the first terminal and the second terminal and are thus able to conduct electricity between the first terminal and the second terminal. In this intact condition, the sensor foil has a certain electrical resistance that corresponds to the combined electrical resistance of all wires. This overall electrical resistance may, upon computing with the transmitter device, thereby correspond to the transmitting of the reference sensor signal.

However, when the sensor foil is damaged, one or more of the wires may become broken. As a result, the overall electrical resistance between the first terminal and the second terminal may change. Hence, fewer wires are able to conduct electricity between the first terminal and the second terminal. This change in overall electrical resistance may be detected by the transmitter device and may result in a change of the sensor signal, which becomes different from the reference sensor signal.

In particular, the sensor signal may be proportional with the severity of the damaging of the sensor foil. Hence, a minor damage of the sensor foil may result in breakage of a single wire and thus to a small increase in the overall electrical resistance of the sensor foil and a minor change in sensor signal. On the other hand, more severe damaging of the sensor, e.g. breakage of several wires, may result in a larger increase in electrical resistance, and thus to a larger change in sensor signal.

In an embodiment, the first electrode and/or the second electrode is formed by a two- dimensional wire mesh, comprising one or more first wires, which are aligned in a first direction, and one or more second wires, which are aligned in a second direction, wherein the second direction is non-parallel with the first direction. The wire mesh thereby forms a planer electrode that is spanned by both sets of wires. The provision of several wires may provide the effect that, compared to a solid and even electrode, less conductive material may be used, but that the respective electrode may still have sufficient coverage across the entire surface of the sensor to ensure proper functioning of the sensor. This configuration may be in particular suited to detect short-circuiting between the one or more first wires and the one or more second wires. In a further embodiment, the first direction is at a right angle with the second direction. The one or more first wires thereby extend in a direction that is perpendicular to the direction in which the one or more second wires extend.

In an embodiment, the at least one electrode is made of a copper alloy material. Such a copper alloy material has a good electrical conductivity and a low electrical resistivity. Accordingly, a change in integrity of the sensor foil will, relatively spoken, result in a large change in electrical resistance of the entire sensor, due to the normally low resistivity of the copper.

In an embodiment, the sensor comprises an adhesive, with which the sensor is adapted to be mounted over the wall feedthrough fitting. The adhesive may be applied on the sensor and may, prior to the application of the sensor onto the wall, be covered with a release layer.

The adhesive is a heat-detachable adhesive, which is configured to detach when an ambient temperature reaches a predefined threshold temperature. The sensor may thus be firmly attached to the wall when the temperature is below the predefined threshold temperate, e.g. during normal conditions. However, when the temperature increases above the predefined threshold temperature, the bonding force of the adhesive is reduced and the sensor come loose from the wall.

This loosening is convenient in case a fire is present in the room. In such a situation, the wall feedthrough fitting is required to prevent flames from passing through the wall. It may then be desired to expose the fitting to the fire directly, without being covered by the sensor. The adhesive is thereby selected such, that the predefined temperature level is above normal ambient temperature conditions, for example being more than 50°C, but below temperature levels that typically occur when a fire is present in the room, for example being lower than 200°C. In that example, the adhesive at least detaches in case of a fire, when the temperature increases above 200°C, in order to ensure proper an non-obstructed functioning of the fire-resistant and/or flame-retardant wall feedthrough fitting, for example one that comprises a fire-resistant and/or flame-retardant foam that then is able to freely and efficiently expand when heated, such that the flames are prevented from passing through the feedthrough.

In an embodiment, the transmitter device comprises an antenna for establishing a wireless connection via which the sensor signal can be transmitted. The transmitter device may thereby be located a distance from a receiver device and does not necessarily need to be physically connected to the receiver device, such as with a wire. The present invention further provides a sensor for a wall feedthrough fitting monitoring device as described above. This sensor is configured to be mounted at the respective wall in which a wall feedthrough fitting is provided. The at least one sensor will be mounted such, that it at least partially covers an area of the respective wall underneath which the wall feedthrough fitting is provided. The at least one sensor may thereto be provided at only one side of the wall, which is a particularly suitable location to detect newly-applied through holes in the wall. In case it is also desired to detect minor damages of the fitting, a sensor may need to be applied at both sides of the wall, in order to detect damages at both sides.

The at least one sensor is electrically connectable to a transmitter device of the monitoring device, e.g. in a manner that allows transmission of a signal from the sensor towards the transmitter device. The transmitter device may as well be connected to more than a single sensor, for example to two sensors for the same fitting, but on opposite sides of the wall.

The transmitter device may be configured to transmit a signal that is representative for the integrity of the sensor, and thus for the integrity of the respective wall feedthrough fitting on which the sensor is mounted. Hence, damaging of the wall feedthrough fitting from the outside would also cause damaging of the sensor that is mounted on top of the wall, e.g. over the fitting.

The present invention further provides a fire-resistance and/or flame-retardance monitoring system for monitoring the fire-resistance and/or flame-retardance of a building, the system comprising: one or more monitoring devices as described above, a user dashboard, a control unit, connected to the user dashboard, and an alarm device, connected to the control unit.

The system is configured to establish a connection, in particular a wireless connection, between the transmitter device of the monitoring device and the user dashboard and the sensor signal of the transmitter device is transmittable from the monitoring device to the user dashboard over the connection.

The control unit is configured to compare the transmitted sensor signal with a reference sensor signal that is representative for the sensor in an intact condition and is configured to activate the alarm device to issue an alarm signal when the sensor signal is different from the reference sensor signal, in order to indicate a reduction in the integrity of the sensor and damaging of the fitting. The monitoring system thus is configured to monitor the integrity of the fire-resistant and/or flame-retardant wall feedthrough fitting in an automated manner and to issue an alarm signal when the wall feedthrough fitting is damaged. As such, it is no longer required to carry out manual inspections in a periodic manner, but the monitoring may rather be carried out continuously and autonomously.

With the system according to the invention, it may be even obsolete to have a person actively monitoring the sensor signals from all transmitter devices within the system for observing irregularities, e.g. non-reference signals, because alarm signals may now be issued automatically. The monitoring is thereby less labour intensive and less prone to failures, in particular human failures, which enhances the certainty with which the fire- resistance and/or flame-retardance of the building can be assured.

The transmitter device is configured to transmit a signal that is representative for the integrity of the sensor, and thus for the integrity of the respective wall feedthrough fitting on which the sensor is mounted. Hence, damaging of the wall feedthrough fitting from the outside would also cause damaging of the sensor that is mounted on top of the wall, e.g. over the fitting.

The user dashboard may comprise a cloud network and/or an application on a mobile device, in which the statuses of one or more of the wall feedthrough fittings are displayed, to quickly observe whether they are still intact and in working order, or whether they are damaged and in need of repair.

According to a further aspect, the present invention provides a method for monitoring the fire- resistance and/or flame-retardance of a building, comprising the steps of: providing a monitoring device as described above, mounting the sensor over a fire-resistant and/or flame-retardant wall feedthrough fitting that is to be monitored, establishing a connection, in particular a wireless connection, between the transmitter device and a user dashboard, transmitting, with the transmitter device, a sensor signal that is representative for the electrical resistance of the at least one electrode of the sensor, comparing, with a control unit, the transmitted sensor signal with a reference sensor signal that is representative for the electrical resistance of the sensor in an intact condition, determining whether the sensor signal differs from the reference sensor signal, in order to indicate a reduction in the integrity of the sensor, and in case the sensor signal differs from the reference sensor signal, activating an alarm device to issue an alarm signal, in order to flag damaging of the fire-resistant and/or flame- retardant wall feedthrough fitting. The method according to the invention may be carried out with the fire-resistance and/or flame-retardance monitoring system that is described above and enables detection of damages to fire-resistant and/or flame-retardant wall feedthrough fittings. The monitoring may be carried out autonomously by means of the sensor that is mounted on the wall and over the fire-resistant and/or flame-retardant wall feedthrough fitting, in order to reduce the human effort that is required in the manual prior art monitoring methods and to improve the accuracy of the monitoring.

In an embodiment, the method comprises the repeating of the steps of transmitting, comparing and determining until the sensor signal differs from the reference sensor signal. This repetition enables repeated monitoring of the wall feedthrough device, and can be carried out after each predetermined time interval. This may reduce the time between measurement, or, in the case of continuous measuring, even completely abates a waiting time in between subsequent measurements, in order to enhance the certainty with which the fire-resistance and/or flame-retardance of the building can be assured.

In an additional or alternative embodiment, the step of mounting the sensor comprises the mounting by means of an adhesive. The adhesive is a heat-detachable adhesive, which is configured to detach when an ambient temperature reaches a predefined threshold temperature. The sensor may thus be firmly attached to the wall when the temperature is below the predefined threshold temperate, e.g. during normal conditions. However, when the temperature increases above the predefined threshold temperature, the bonding force of the adhesive is reduced and the sensor come loose from the wall.

This loosening is convenient in case a fire is present in the room. In such a situation, the wall feedthrough fitting is required to prevent flames from passing through the wall. It may then be desired to expose the fitting to the fire directly, without being covered by the sensor. The adhesive is thereby selected such, that the predefined temperature level is above normal ambient temperature conditions, for example being more than 50°C, but below temperature levels that typically occur when a fire is present in the room, for example being lower than 200°C. In that example, the adhesive at least detaches in case of a fire, when the temperature increases above 200°C, in order to ensure proper and non-obstructed functioning of the fire-resistant and/or flame-retardant wall feedthrough fitting, for example one that comprises a fire-resistant and/or flame-retardant foam that then is able to freely and efficiently expand when heated, such that the flames are prevented from passing through the feedthrough. Finally, the present invention also provides the use of a fire- resistance and/or flame- retardance monitoring system, as described above, for monitoring the fire-resistance and/or flame-retardance of a building.

Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:

Figure 1 depicts a plan view on an embodiment of the wall feedthrough fitting monitoring device according to the present invention,

Figure 2 depicts an exploded-view on the sensor of the device in figure 1 ,

Figure 3 depicts an embodiment of a fire-resistance and/or flame-retardance monitoring system according to the present invention, and

Figure 4 depicts a wall feedthrough fitting monitoring device in an installed configuration.

Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

Figure 1 schematically depicts an embodiment of the wall feedthrough fitting monitoring device according to the present invention, to which is referred with reference numeral 1. The monitoring device 1 comprises a sensor foil 10 and a transmitter device 20. The sensor foil 10 and the transmitter device 20 are electrically connected to each other by means of a cable 2 that extends between both. In figure 1, the sensor foil 10 is displayed in an intact condition, not being damaged. The sensor foil 10 is, at least in figure 1, thin and flat and is therefore flexible, in order to be attached to both smooth walls and rough or uneven walls.

The transmitter device 20 is configured to transmit a sensor signal that is representative for the integrity of the sensor foil 10. In the present embodiment, the transmitter device 20 is configured to compute the electrical resistance of the sensor foil 10 and to transmit the sensor signal on the basis of the computed electrical resistance.

For the intact sensor foil 10, the transmitted sensor signal is a reference sensor signal. Should, however, the sensor foil 10 become damaged after installation over a wall feedthrough fitting, the electrical resistance of the sensor foil 10 may change. Accordingly, the transmitter device 20 will no longer transmit the reference sensor signal, but will rather transmit a different sensor signal.

In figure 2, the sensor foil 10 of figure 1 is displayed as an exploded-view image. The sensor foil 10 comprises a first conductive layer and a second conductive layer. The first conductive layer forms a first electrode 11 of the sensor foil 10 and the second conductive layer forms a second electrode 12 of the sensor foil 10. Both conductive layers comprise a copper alloy material, which allows for a low electric resistivity of the electrodes 11, 12.

In between the electrodes 11, 12, an electrical insulator layer 13 is provided. The insulator layer 13 has a large electrical resistivity, which prevents an electric current between the first electrode 11 and the second electrode 12. The insulator layer 13 has a size that substantially corresponds to the size of both electrodes 11, 12, which provides that electric contact between the electrodes 11, 12 is prevented across the entire sensor foil 10.

Although the various layers appear to be spaced from one another in the representation in figure 2, both electrodes 11, 12 are in fact in contact with the insulator layer 13. The insulator layer 13 thereby acts as a spacer in between the electrodes 11, 12, in order to set the electrodes 11, 12 at a distance from each other.

In the present embodiment, the first conductive layer and the second conductive layer are provided as flat sheets that closely abut the insulator layer 13. In an alternative embodiment, the first electrode 11 and the second electrode 12 are printed on the insulator layer 13. Such a printed structure may have the benefit that less conductive material may be used, when compared to the flat and even layers in figure 2, but that the respective conductive layers may still have sufficient coverage across the insulator layer to ensure proper functioning of the sensor foil.

It is further displayed in figure 2 that the cable 2 comprises a first wire 3 that extends towards the first electrode 11 and a second wire 4 that extends towards the second electrode 12. Both electrodes 11, 12 are thereby configured to be individually connected to the transmitter device 20. The transmitter device 20 is, in turn, configured to compute an overall electric resistance between the first electrode 11 and the second electrode 12.

In the intact configuration of figure 1 , the electrical resistance of the sensor foil 10 is relatively large. This is not attributable to the wires 3, 4 or the electrodes 11, 12, since those have a relatively low resistivity, for example being made of a copper alloy, but is rather due to the insulator layer 13 in between the electrodes 11, 12.

When the sensor foil 10 were to be damaged, the electrical resistance of the sensor foil 10 may change. The damaging may for example comprises an indentation at either side of the sensor foil 10, which causes the electrodes 11, 12 to be pressed towards each other. This pressure may cause compression of the insulator layer 13 and provides that the distance between the first electrode 11 and the second electrode 12 is reduced. Accordingly, this change in distance may effect a change in electrical resistance between the electrodes 11,

12, thereby causing a different sensor signal to be transmitted by the transmitter device 20.

Damage of the sensor foil 10 may also occur when, for example, the sensor foil 10 were to be punctured by a metallic drill. The drill would then both protrude the first electrode 11 and the second electrode 12, thereby short-circuiting both. Accordingly, the drop in electrical resistance will result in a different sensor signal, no longer being the same as the reference sensor signal.

In figure 3, an embodiment of the fire-resistance and/or flame-retardance monitoring system according to the present invention is displayed, to which is referred with reference numeral 30. The monitoring system 30 comprises a monitoring device 1 with three sensor foils. A first sensor foil 10’ is connected to the transmitter device 20 by means of a first cable 2’, a second sensor foil 10” is connected to the transmitter device 20 by means of a second cable 2” and a third sensor foil 10’” is connected to the transmitter device 20 by means of a third cable 2”’.

The monitoring system 30 further comprises a user dashboard, which is presently embodied as an application 31 on a mobile device, e.g. a smartphone 32. The transmitter device 20 comprises an antenna 21, which is configured to establish a preferably wireless connection with the smartphone 32, via which the sensor signal can be transmitted from the transmitter device 20 towards the application 31.

An operator may monitor the integrity of the sensor foils 10’, 10”, 10”’, and therefore the integrity of the respective wall feedthrough fitting on which they are mounted, remotely on the application 31. The operator does not need to physically examine the respective fitting, but is rather able to check the integrity on the application 31 on his smartphone 32. Apart from being less labour intensive, this remote monitoring may also be less prone to failures, in particular human failures, and can be carried more often or even continuously, which enhances the certainty with which the integrity of the fire-resistant and/or flame-retardant wall feedthrough fitting can be assured.

In figure 4, a wall feedthrough fitting monitoring device is schematically displayed in an installed configuration on a wall 100. The wall 100 comprises a hole, through which a pipe 101 extends. The pipe 101 is guided through the wall 100 by means of a fire-resistant and/or flame-retardant wall feedthrough fitting, of which a collar 102 is visible, being disposed against the wall 100.

The monitoring device 1 is mounted over the fitting which its sensor foil 10, which is attached to the wall 100 by means of an adhesive. The sensor foil 10 comprises an aperture 14 that inwardly protrudes from the side of the sensor foil 10. In the installed configuration, the sensor foil 10 is positioned with respect to the pipe 101 in such a manner, that the aperture 14 surrounds the pipe 101 and that remaining parts of the sensor foil 10 cover the fitting. The transmitter device 20 is also mounted on the wall 100 and is positioned adjacent to the sensor foil 10 and connected to the sensor foil 10 by means of the cable 2.