DE102009034633A1 - Sensor assembly useful in ventilation system of vehicle air-conditioner comprises housing having first and second measurement chambers that are gas-tightly separated in the housing, and electronic processor for evaluating all sensor data - Google Patents

Abstract

The sensor assembly (10) of a ventilation system of a vehicle air-conditioner comprises a housing (14), in which a first measurement chamber (18) is provided with a carbon monoxide sensor and/or a nitrogen oxide sensor and a second measurement chamber (28) is provided with a carbon dioxide sensor, and an electronic processor for evaluating all sensor data. The first and second measurement chambers are gas-tightly separated in the housing. An air humidification sensor and a temperature sensor are provided in the first and/or second measurement chambers. The sensor assembly (10) of a ventilation system of a vehicle air-conditioner comprises a housing (14), in which a first measurement chamber (18) is provided with a carbon monoxide sensor and/or a nitrogen oxide sensor and a second measurement chamber (28) is provided with a carbon dioxide sensor, and an electronic processor for evaluating all sensor data. The first and second measurement chambers are gas-tightly separated in the housing. An air humidification sensor and a temperature sensor are provided in the first and/or second measurement chambers. A gas sensor is provided in the first measurement chamber for detecting odorous substances perceptible from human. A third chamber is provided between the first and second chambers and is gas-tightly separated from the both measurement chambers. The sensor assembly has a common electrical connecting point. The first and second measurement chambers have gas entrance openings (16), which are arranged at opposite sides of the housing and flow into the associated measurement chambers. Independent claims are included for: (1) a ventilation system for a vehicle air-conditioner; and (2) a method for controlling a ventilation system for a vehicle air-conditioner.

Description

The The invention relates to a sensor assembly of a ventilation system a vehicle interior, such a ventilation system, in particular a vehicle air conditioning system, and a method for controlling a such ventilation system.

Ventilation systems, z. B. in the form of air conditioning systems, in particular HVAC systems, for vehicle interiors in diverse Designs known. In particular, air conditioners are known that use various sensor data are controlled. The sensors for detection This sensor data are at various locations in the vehicle interior arranged, reducing the construction and installation of the ventilation system are complex and expensive.

task The invention is a simplified sensor assembly for a ventilation system to accomplish. Further objects of the invention are a simply constructed ventilation system with a sensor assembly for controlling the ventilation system and a beneficial Specify method for controlling a ventilation system.

The object of the invention is achieved by a sensor assembly comprising a housing in which a first measuring chamber with a CO sensor and / or NO _x sensor and a second measuring chamber are provided with a CO ₂ sensor, wherein the first and the second measuring chamber in the housing are gas-tight separated. Such a sensor assembly enables the acquisition of various measurement data through a single sensor assembly, where multiple sensors are compactly housed in a single housing. The sensor assembly according to the invention can be installed as a self-contained, preassembled unit in a simple manner in a ventilation system.

advantageously, can additional sensors provided in the measuring chambers of the sensor assembly be, resulting in a variety of readings through a single sensor assembly can be detected. For example, an air humidity sensor be provided in the first and / or second measuring chamber.

It is possible, too, a temperature sensor is provided in the first and / or second measuring chamber is.

Furthermore can at least one gas sensor for the detection of human perceptible Odors are provided in the first measuring chamber. This allows the Control of the ventilation system dependent on of certain odorous substances, such as agricultural ones Smells, especially the smell of manure, or the smell of skunk.

According to one preferred embodiment an electronic processing unit for the evaluation of all sensor data intended. Thus it is not necessary to use the different sensors individually connected to a separate control unit of the ventilation system and The electronic processing unit can be optimally adapted to the existing ones Sensors are adapted and allows, for example, a direct evaluation of the sensor data and a related determination of control parameters for controlling the ventilation system.

A third chamber may be provided between the first and second measuring chambers be, each of which is gas-tight separated from the two measuring chambers. In this way, on the one hand, an arrangement of the electronic Arithmetic unit in the third chamber allows and on the other hand the Improved sealing between the first and second measuring chamber.

Preferably the sensor arrangement has a common electrical connection point on. this makes possible a simple connection of all sensors of the sensor assembly the ventilation system.

According to one preferred embodiment the first and second measuring chambers each gas inlet openings on that on opposite Sides of the case are arranged and open into the associated measuring chambers. This allows a simple embodiment the sensor assembly, in which the various measuring chambers on their respective gas inlet openings with different areas of the ventilation system or the vehicle interior can be connected.

In addition, the object of the invention by a ventilation system for a vehicle interior, in particular a vehicle air conditioner, having a fresh air duct and a sensor assembly described above, wherein the first measuring chamber via a gas inlet opening leading to the vehicle interior fresh air duct and the second measuring chamber via a gas inlet opening communicates with the vehicle interior. The ventilation system according to the invention thus enables a measurement of CO ₂ in the vehicle interior and a measurement of CO and / or NO _x in the fresh air duct. It can thus be determined with a single sensor module both the air quality in the vehicle interior and the air quality in the fresh air duct. Due to the ventilation system according to the invention, the housing of the system and the sensor assembly are a mounting unit.

The second measuring chamber can over a gas inlet opening with an air return channel and thus communicate with the vehicle interior.

According to one preferred embodiment of Invention is the sensor assembly in or on a wall of the fresh air duct arranged. this makes possible a direct connection of the first measuring chamber to the moving air in the fresh air channel.

For example the sensor assembly is disposed within a housing of the air conditioner. In this way, the sensor assembly in the housing of the air conditioning pre-assembled which allows the installation of the ventilation system into the vehicle is simplified.

According to one another embodiment is the sensor assembly in or on an outer wall of a housing of the Air conditioning arranged. this makes possible a simple connection of the second measuring chamber with the vehicle interior.

The Sensor assembly can with their second measuring chamber in the vehicle interior protrude, causing the coupling of the second measuring chamber with the vehicle interior is more direct.

advantageously, is the case the air conditioning attached to a vehicle spray wall. The sensor Can then possibly through the bulkhead in the vehicle interior protrude.

Preferably is the sensor assembly over one singular Wiring harness connected to a control unit of the ventilation system. This allows one simple and clear Wiring of the ventilation system.

The invention further relates to a method for controlling a ventilation system for a vehicle interior, in particular a vehicle air conditioning system, with an automatic control unit for a fresh air / recirculation flap, which according to the invention comprises the following steps: a CO ₂ concentration in the vehicle interior and a CO and / or NO _x concentration in a fresh air duct is measured. An at least partial opening of the fresh air / recirculating air flap takes place if the CO ₂ concentration is above a first predetermined CO ₂ concentration limit and the CO and / or NO _x concentration is below a predetermined upper limit of exhaust gas concentration; a closing of the fresh air / circulating air flap takes place if the CO and / or NO _x concentration is above the upper limit of the exhaust gas concentration; and an at least partial opening of the fresh air / recirculated-air flap takes place if the CO ₂ concentration is above a predetermined CO ₂ maximum. The control of the ventilation system thus takes place both as a function of the CO ₂ concentration in the vehicle interior and in dependence on the CO and / or NO _x concentration in the fresh air duct. On the one hand, the control makes it possible to automatically switch the ventilation system into the recirculation mode with a high exhaust gas concentration in the fresh air channel, for example if the vehicle is in a traffic jam or in a tunnel, and on the other hand to automatically switch the ventilation system to a fresh air supply, if the CO ₂ Concentration in the vehicle interior increases, whereby fatigue symptoms of the vehicle occupants are prevented at too high a CO ₂ concentration. Through the combined measurement of the CO ₂ and exhaust gas concentration, the controller can control the ventilation system at mean CO ₂ values as a function of the exhaust gas concentration.

According to one Another variant of the method is in a fresh air channel from the Humans perceivable odorant measured, and the control unit controls the fresh air / recirculation flap depending on the results Odor measurement, in particular by closing the Fresh air / recirculation flap on detection of the odorant. To this Way, a penetration of evil smelling odors, such as agricultural Smells, especially manure, or the smell of skunk through the ventilation system into the vehicle interior be prevented.

Preferably, in the recirculation mode of the ventilation system, the control unit opens the fresh air / recirculation flap at least partially, if no odorant is detected and the CO ₂ concentration is above a predetermined second CO ₂ concentration limit, the second CO ₂ concentration limit preferably below the first CO ₂ concentration limit and the CO ₂ maximum. In this way, at a predetermined CO ₂ concentration, in particular in the lower central region, an automatic switching between recirculation and fresh air operation of the ventilation system in response to a detected odorant can be performed.

The ventilation system is advantageously operated in the ground state in the recirculation mode. In this way, the ventilation system especially in a heating or cooling of the air energy-saving work, since in recirculation already heated or cooled air is heated or cooled from the vehicle interior.

Further Features and advantages of the invention will become apparent from the following Description and from the following drawings, to the reference is taken. In the drawings show:

1 a schematic sectional view through a sensor assembly according to the invention;

2 a perspective view of the sensor assembly according to 1 ;

3 the sensor assembly according to 2 with open housing;

4 a ventilation system according to a first embodiment of the invention;

5 a side sectional view of the ventilation system according to 4 along the sectional plane VV with several mounting positions of the sensor assembly; and

6 a ventilation system according to a second embodiment of the invention.

1 shows a sensor assembly 10 standing in a wall 12 is arranged. The wall 12 may be part of a housing of a vehicle air conditioner or a fresh air duct, for example. The sensor assembly 10 forms a self-contained, preassembled unit in the wall 12 is installed, in particular interchangeably attached to it.

The sensor assembly 10 includes a housing 14 with two gas inlet openings 16 , each on one side of the wall 12 on opposite sides of the housing 14 are arranged.

On the right side of the sensor assembly 10 is a first measuring chamber 18 provided over the right gas inlet opening 16 with the room to the right of the wall 12 connected is.

In the first measuring chamber 18 is a CO and NO _x sensor 20 attached, the a CO and NO _x concentration through the gas inlet opening 16 can measure incoming air. It may also be just a CO sensor or just a NO _x sensor instead of the combined CO and NO _x sensor shown 20 in the first measuring chamber 18 be provided. Of course, CO sensor and NO _x sensor can also be separate sensors.

Optionally, an additional sensor or can several different additional sensors in the first measuring chamber 18 lie. An additional sensor is in 1 shown with dotted line. This additional sensor can be a humidity sensor 22 , Temperature sensor 24 and / or a gas sensor 26 to detect human perceptible odors.

It can also several gas sensors for the detection of several different ones Odors are provided, for. B. for the determination of agricultural Smells, especially slurry smell, or from Skunk smell.

On the left side of the sensor assembly 10 is a second measuring chamber 28 provided, via the left gas inlet 16 with the room to the left of the wall 12 connected is.

In the second measuring chamber 28 is a CO ₂ sensor 30 provided that a CO ₂ concentration through the gas inlet opening 16 entering air from the room to the left of the wall 12 can measure.

An optional dotted-line additional sensor may be an air humidity sensor 22 and / or a temperature sensor 24 be.

A third chamber 32 is in the middle area of the housing 14 the sensor assembly 10 intended. The third chamber 32 lies between the first measuring chamber 18 and the second measuring chamber 28 and is from both chambers 18 . 28 through an intermediate wall 34 gas-tight or at least approximately gas-tightly separated.

In the third chamber 32 is an electronic processing unit 36 arranged. The electronic processing unit 36 is used to evaluate all sensor data from the CO and NO _x sensor 20 , the CO ₂ sensor 30 as well as the optional humidity sensors 22 , Temperature sensors 24 and the gas sensor 26 be detected for the detection of odors.

In 2 and 3 is a perspective view of the sensor assembly 10 in the wall 12 shown, the sensor assembly 10 in 2 with closed housing 14 and in 3 with the housing open 14 is shown. The different sensors are for the sake of clarity in the 2 and 3 Not shown.

At the housing 14 is on the left side of the wall 12 a common electrical connection point 38 intended. The electrical connection point 38 on the one hand supplies the electronic processing unit 36 and on the other hand, if needed, the various sensors 20 . 22 . 24 . 26 . 30 in the two measuring chambers 18 . 28 with power and on the other hand serves to transmit the sensor data and / or control parameters of the electronic processing unit 36 For example, on a control unit of a ventilation system.

4 shows a first embodiment of a ventilation system 40 for a vehicle interior, which is designed in the embodiment shown as a vehicle air conditioning system, in particular HVAC system.

A vehicle splash wall 42 separates a vehicle interior 44 from a vehicle exterior communicating with fresh air 46 For example, the engine compartment of the vehicle. A fresh air channel 48 leads from the vehicle exterior 46 to a fresh air / recirculation flap 50 ,

After the fresh air / circulating air flap 50 leads an air supply duct 52 the air to an air conditioner 54 in which the air can be filtered, heated or cooled and the humidity can be regulated, and by the air conditioning 54 in the vehicle interior 44 , The air conditioner 54 is with her case 55 at the vehicle splash wall 42 attached.

Optionally, a dotted line air return duct 56 the vehicle interior 44 with the fresh air / recirculation flap 50 connect.

A sensor assembly described above 10 is in the wall 12 of the fresh air channel 48 built-in. The sensor assembly 10 is arranged so that the first measuring chamber 18 with the fresh air duct 48 connected and the second measuring chamber 28 in the vehicle interior 44 protrudes and over its gas inlet opening 16 with the vehicle interior 44 connected is.

5 shows a side sectional view of the ventilation system 40 along the in 4 shown section plane VV. The fresh air / recirculation flap 50 is shown with a solid line in its closed position and with a dashed line in its open position.

The sensor assembly 10 is in a first preferred installation position 61 in the wall 12 of the fresh air channel 48 in front of the fresh air / circulating air flap 50 arranged. But there may be other installation positions 62 . 63 for a sensor assembly 10 be provided. The sensor assembly 10 is in the second installation position 62 after the fresh air / circulating air flap 50 with bypass for a fresh air supply through the fresh air / circulating air flap 50 or on a housing of the ventilation system 40 arranged. The sensor assembly 10 is in the third installation position 63 at the fresh air / circulating air flap 50 appropriate.

6 shows a second embodiment of a ventilation system 40 which is formed substantially analogously to the first embodiment. The sensor assembly 10 is in a wall 12 of the fresh air channel 48 in front of the fresh air / circulating air flap 50 provided, with the wall 12 at the same time the wall of the air return duct 56 is.

The first measuring chamber 18 is with the fresh air duct 48 connected while the second measuring chamber 28 with the air return duct 56 connected is. The sensor assembly 10 is in the air return channel 56 in front of the fresh air / circulating air flap 50 arranged, whereby the second measuring chamber 28 with the vehicle interior 44 connected is.

In particular, it is also possible that the fresh air / recirculated air flap 50 inside the case 55 the air conditioning 54 is arranged, causing the sensor assembly 10 inside the housing of the air conditioner 54 can be arranged. The sensor assembly 10 Also in or on an outside wall of the housing of the air conditioner 54 be arranged. With broken lines in this embodiment is the sensor assembly 10 shown. The housing 55 may possibly also the channels 52 . 56 and possibly 48 (see enclosure extension with broken lines in 6 )

The sensor assembly 10 is via a singular harness with a control unit of the ventilation system 40 connected. The control unit of the ventilation system 40 can be a locking mechanism of the fresh air / recirculation flap 50 and / or a control unit of the air conditioning 54 be.

The following is a method of controlling the ventilation system 40 for a vehicle interior 44 using the example of in 4 shown ventilation system 40 as well as the functioning of the in the 1 to 3 shown sensor assembly 10 explained.

In a first process step, a CO ₂ concentration in the vehicle interior 44 through the CO ₂ sensor 30 in the second measuring chamber 28 the sensor assembly 10 measured. At the same time, a CO and NO _x concentration is produced by the CO and NO _x sensor 20 in the first measuring chamber 18 the sensor assembly 10 in the fresh air duct 48 measured. The sensor data are processed by the electronic processing unit 36 the sensor assembly 10 detects an automatic control unit for the fresh air / recirculation flap 50 forms.

If the CO ₂ concentration is above a first predetermined CO ₂ concentration limit and the CO and NO _x concentration is below a predetermined exhaust gas upper concentration limit, the fresh air / recirculated air flap 50 at least partially open, and the vehicle interior 44 Fresh air is supplied to the CO ₂ concentration in the vehicle interior 44 to lower.

If the CO and / or NO _x concentration is above the upper limit of the exhaust gas concentration, the fresh air / recirculated air flap becomes 50 closed to suction of harmful CO and NO _x emissions through the ventilation system 40 to avoid.

If the CO ₂ concentration is above a predetermined CO ₂ maximum, the fresh air / recirculated air flap 50 regardless of the other sensor data, at least partially open to a high CO ₂ concentration in the vehicle interior 44 to avoid.

A high CO ₂ concentration can cause fatigue in the vehicle occupants. For example, a value of 2,500 ppm can be selected for the predetermined CO ₂ maximum, for example a value of 800 ppm for the first predetermined CO ₂ concentration limit. Of course, other CO ₂ concentrations for the CO ₂ maximum and the first predetermined CO ₂ concentration limit can be predetermined.

Is one or more optional gas sensors 26 for the detection of odors in the first measuring chamber 18 the sensor assembly 10 provided, are perceptible by humans odors in the fresh air channel 48 measured, in particular odors (agricultural odors, for example, manure smell and Skunkgeruch). The electronic processing unit 36 controls in this case the fresh air / circulating air flap 50 depending on the odor measurement, wherein upon detection of an odorant, the fresh air / recirculation flap 50 is closed.

Preferably, the control of the fresh air / circulating air flap takes place 50 by combining the sensor data of the CO ₂ sensor 30 and the gas sensors 26 for the detection of odors. The control unit opens in the recirculation mode of the ventilation system 40 the fresh air / circulating air flap 50 at least in part, if the CO ₂ concentration is above a predetermined second CO ₂ concentration limit and if no odorant is detected. The second CO ₂ concentration limit is preferably below the first CO ₂ concentration limit and the CO ₂ maximum.

In a particularly preferred control method for the ventilation system 40 becomes the ventilation system 40 in the ground state in recirculation mode, with closed fresh air / recirculation flap 50 , operated. In this way, energy is saved, in particular during operation of the ventilation system with a heating or cooling of the air, since in the recirculation mode already preheated or pre-cooled air is further warmed up or cooled.

For prolonged operation of the ventilation system 40 In recirculation mode, the CO ₂ concentration of the air inside the vehicle increases 44 due to the breathing gases of the vehicle occupants over time.

When the CO ₂ concentration reaches the second CO ₂ concentration limit, the control unit opens the fresh air / circulating air flap 50 on the condition that no unwanted, perceptible by humans odors in the fresh air duct 48 be detected. If, for example, liquid manure smell is detected, the fresh air / circulating air flap remains 50 closed.

With further increase in the CO ₂ concentration, the first predetermined CO ₂ concentration limit is reached, wherein the fresh air / recirculated air flap 50 by the control unit, under the condition that the CO ₂ and NO _x concentrations are below a respective predetermined exhaust gas concentration upper limit, is at least partially opened. In this way it is prevented that high, harmful exhaust gas concentrations through the ventilation system 40 in the vehicle interior 44 be directed.

If the CO ₂ concentration reaches the predetermined CO ₂ maximum, then the fresh air / recirculated air flap 50 regardless of the other sensor data at least partially open.

At CO ₂ concentrations in the vehicle interior 44 under the first predetermined CO ₂ -Konzentrationsgrenze the vehicle occupants are thus protected from exhaust gases and unpleasant odors, while at CO ₂ concentrations between the first predetermined CO ₂ concentration limit and the predetermined CO ₂ maximum, the vehicle occupants are protected only against harmful exhaust gases and a Odor nuisance in favor of a reduced CO ₂ concentration is accepted.

It is of course possible, the degree of opening of the fresh air / circulating air flap 50 and thus to control the proportion of fresh air relative to the circulating air by the control unit in dependence of all sensor data.

The sensor data of the humidity sensors 22 and temperature sensors 24 can also be used to the air conditioning 54 energy-saving with optimized performance.

Claims (21)

Sensor assembly ( 10 ) of a ventilation system ( 40 ) of a vehicle interior ( 44 ), in particular a vehicle air conditioning system with a housing ( 14 ), in which a first measuring chamber ( 18 ) with a CO sensor ( 20 ) and / or NO _x sensor ( 20 ) and a second measuring chamber ( 28 ) with a CO ₂ sensor ( 30 ) are provided, wherein the first and the second measuring chamber ( 18 . 28 ) in the housing ( 14 ) are separated gas-tight. Sensor assembly ( 10 ) according to claim 1, characterized in that a Luftfeuchtigkeitssen sor ( 22 ) in the first and / or second measuring chamber ( 18 . 28 ) is provided. Sensor assembly ( 10 ) according to claim 1 or 2, characterized in that a temperature sensor ( 24 ) in the first and / or second measuring chamber ( 18 . 28 ) is provided. Sensor assembly ( 10 ) according to one of the preceding claims, characterized in that at least one gas sensor ( 26 ) for the detection of human perceptible odors in the first measuring chamber ( 18 ) is provided. Sensor assembly ( 10 ) according to one of the preceding claims, characterized in that an electronic processing unit ( 36 ) is provided for the evaluation of all sensor data. Sensor assembly ( 10 ) according to one of the preceding claims, characterized in that a third chamber ( 32 ) between the first and second measuring chambers ( 18 . 28 ) is provided, each gas-tight from the two measuring chambers ( 18 . 28 ) is disconnected. Sensor assembly ( 10 ) according to one of the preceding claims, characterized in that the sensor assembly ( 10 ) a common electrical connection point ( 38 ) having. Sensor assembly ( 10 ) according to one of the preceding claims, characterized in that the first and second measuring chambers ( 18 . 28 ) each gas inlet openings ( 16 ) on opposite sides of the housing ( 14 ) are arranged and in the associated measuring chambers ( 18 . 28 ). Ventilation system ( 40 ) for a vehicle interior ( 44 ), in particular vehicle air conditioning system, with a fresh air duct ( 48 ) and a sensor assembly ( 10 ) according to one of the preceding claims, wherein the first measuring chamber ( 18 ) via a gas inlet opening ( 16 ) with the vehicle interior ( 44 ) leading fresh air channel ( 48 ) and the second measuring chamber ( 28 ) via a gas inlet opening ( 16 ) with the vehicle interior ( 44 ). Ventilation system ( 40 ) according to claim 9, characterized in that the second measuring chamber ( 28 ) via a gas inlet opening ( 16 ) with an air return duct ( 56 ). Ventilation system ( 40 ) according to claim 9 or 10, characterized in that the sensor assembly ( 10 ) in or on a wall ( 12 ) of the fresh air channel ( 48 ) is arranged. Ventilation system ( 40 ) according to one of claims 9 to 11, characterized in that the sensor assembly ( 10 ) in front of or in a fresh air / circulating air flap ( 50 ) is arranged. Ventilation system ( 40 ) according to one of claims 9 to 12, characterized in that the sensor assembly ( 10 ) within an enclosure of the air conditioner ( 54 ) is arranged. Ventilation system ( 40 ) according to one of claims 9 to 12, characterized in that the sensor assembly ( 10 ) in or on an outer wall of a housing of the air conditioner ( 54 ) is arranged. Ventilation system ( 40 ) according to one of claims 9 to 14, characterized in that the sensor assembly ( 10 ) with its second measuring chamber ( 28 ) in the vehicle interior ( 44 protrudes. Ventilation system ( 40 ) according to one of claims 9 to 15, characterized in that the housing of the air conditioning ( 54 ) on a vehicle spray wall ( 42 ) is attached. Ventilation system ( 40 ) according to one of claims 9 to 16, characterized in that the sensor assembly ( 10 ) via a singular cable harness with a control unit of the ventilation system ( 40 ) connected is. Method for controlling a ventilation system ( 40 ) for a vehicle interior ( 44 ), in particular for controlling a vehicle air conditioning system with an automatic control unit for a fresh air / recirculation flap ( 50 ), characterized by the method steps: a) Measurement of a CO ₂ concentration in the vehicle interior ( 44 ); b) Measurement of a CO and / or NO _x Concentration in a Fresh Air Channel ( 48 ); c) at least partially opening the fresh air / circulating air flap ( 50 ) if the CO ₂ concentration is above a first predetermined CO ₂ concentration limit and the CO and / or NO _x concentration is below a predetermined exhaust gas concentration upper limit; d) closing the fresh air / circulating air flap ( 50 ) if the CO and / or NO _x concentration is above the exhaust gas concentration upper limit; e) at least partially opening the fresh air / recirculating air flap ( 50 ), if the CO ₂ concentration is above a predetermined CO ₂ maximum. Method according to claim 18, characterized in that in a fresh air duct ( 48 ) a human perceptible odorant is measured and the control unit the fresh air / recirculation flap ( 50 ) depending on the smell material measurement controls, in particular by closing the fresh air / recirculation flap ( 50 ) upon detection of the odorant. A method according to claim 18 and 19, characterized in that the control unit in recirculation mode of the ventilation system ( 40 ) the fresh air / circulating air flap ( 50 ) opens at least partially, if no odorant is detected and the CO ₂ concentration is above a predetermined second CO ₂ concentration limit, wherein the second CO ₂ concentration limit is preferably below the first CO ₂ concentration limit and the CO ₂ maximum. Method according to one of claims 18 to 20, characterized in that the ventilation system ( 40 ) is operated in the ground state in the recirculation mode.

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