JP2007271636A - Gas detecting device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide gas detecting technique capable of easily detecting the presence of a volatile organic compound of a low concentration of from several ppm to several ppb, at high sensitivity. <P>SOLUTION: A gas detecting device comprises a sensor element having a heater layer for heating a gas detecting layer, which is formed by making an SnO<SB>2</SB>film as the gas sensing layer, on the surface of the gas sensing layer on the support substrate of a diaphragm structure in which a thin film-like support film is supported by a supporting member, and then by making a selective combustion layer on the surface of the gas sensing layer; an energizing and driving means for energizing and driving the heater layer so that the temperature of the gas sensing layer changes from the low-temperature state to the high-temperature state; and a sensing section for detecting the presence of the volatile organic compound from the electric resistance value when the temperature of the gas sensing layer changes to the high-temperature state, in which, after starting energizing and driving, the volatile organic compound is detected by using the electric resistance value in the range of a predetermined elapsed time, in which the detection sensitivity of the gas sensing layer to the volatile organic compound is meaningfully obtained to air. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a film-like oxide whose electrical resistance value varies depending on the presence or absence of a detection target gas on a support substrate having a diaphragm structure in which an outer peripheral portion or both end portions of a thin support film are supported by a support member, and A sensor element in which an energization heating body for heating the film-like oxide is formed; and an energization driving means for energizing and driving the energization heating body so that the temperature of the film-like oxide changes from a low temperature state to a high temperature state; A gas detection device including a detection unit that detects the presence or absence of the detection target gas based on an electric resistance value of the film oxide when the temperature of the film oxide is changed to a high temperature state, and the gas More particularly, the present invention relates to a gas detection device for detecting a volatile organic compound such as formaldehyde as a detection target gas.

The volatile organic compound (VOC) as described above is an organic compound having a boiling range of 0 to 380 ° C. As such a volatile organic compound, alcohols including ethanol and methanol, aldehydes including formaldehyde and acetaldehyde are used. And ketones containing acetone. Among them, volatile organic compounds such as formaldehyde, toluene, xylene, chloroform, and paradichlorobenzene have a concentration of several ppm to several ppb which is not felt by human olfaction. It has been pointed out that living in such an atmosphere for a long time causes health damage.
And along with recent high airtightness of houses, there is a problem that a low concentration of gaseous volatile organic compound exists in the air for a long time in the house.

  However, there is no effective gas detection device that can detect with high sensitivity that a low-concentration volatile organic compound is present in the air, and such a gas detection device is desired.

  Therefore, in view of the above circumstances, the present invention provides a gas detection technique that can easily and easily detect the presence of a low concentration volatile organic compound such as several ppm to several ppb in the air. The purpose is to provide.

[Configuration 1]
In order to achieve the above object, the gas detection device according to the present invention is such that the outer peripheral portion or both ends of the thin film-like support film are supported by the support member as described in claim 1 of the claims. An SnO ₂ film as a gas detection layer is formed on a support substrate having a diaphragm structure, and a selective combustion layer is formed on the surface of the gas detection layer, and a heater layer for heating the gas detection layer is provided. A sensor element;
Energization driving means for energizing and driving the heater layer so that the temperature of the gas detection layer changes from a low temperature state to a high temperature state;
Based on the electrical resistance value of the gas detection layer when the temperature of the gas detection layer is changed to a high temperature state, and a detection unit that detects the presence or absence of a volatile organic compound as a detection target gas,
After the start of energization driving to the heater layer by the energization driving means, the detection unit is within a predetermined elapsed time range in which the detection sensitivity of the gas detection layer with respect to the volatile organic compound is significantly obtained with respect to air. The volatile organic compound is detected using an electric resistance value of the gas detection layer.

In addition, the gas detection method according to the present invention for achieving the above object is suitably executed by the gas detection device having the above-described configuration 1, and as described in claim 7 in the column of claims. An SnO ₂ film as a gas detection layer is formed on a support substrate having a diaphragm structure in which the outer periphery or both ends of the thin support film are supported by a support member, and the selective combustion layer is formed of the gas detection layer. Using a sensor element comprising a heater layer formed on the surface and heating the gas detection layer,
The temperature of the gas detection layer is changed from a low temperature state to a high temperature state by energization driving means for energizing and driving the heater layer,
The electric resistance value of the gas detection layer when the temperature of the gas detection layer is changed to a high temperature state, and the gas detection layer with respect to the volatile organic compound as the detection target gas after the start of energization driving to the heater layer The volatile organic compound is detected by using the electric resistance value of the gas detection layer within a predetermined elapsed time range in which the detection sensitivity of the gas is significantly obtained with respect to air.

[Function and effect]
The inventors of the present application provide a gas detection layer which is a SnO ₂ film as a film-like oxide whose electric resistance value changes depending on the presence or absence of a volatile organic compound as a detection target gas in a sensor element with an extremely low heat capacity, The electric resistance value of the gas detection layer is volatile immediately after the start of energization driving to the heater layer as the energization heating body so that the gas detection layer is changed from the low temperature state where the detection layer is low temperature to the high temperature state where the gas detection layer is high temperature. It was discovered that when a large amount of organic compound is present, it is significantly reduced, and as a result, after the start of energization driving to the heater layer, the gas detection layer in the detection of volatile organic compounds within a predetermined elapsed time range. As a result, the present inventors have completed the present invention.

That is, according to the gas detection device and the gas detection method of Configuration 1, in the detection unit, the electric resistance value of the gas detection layer within the predetermined elapsed time range after the start of energization drive to the heater layer by the energization drive means. Can be used to detect volatile organic compounds.
Here, in the sensor element, a selective combustion layer is formed on the surface of the gas detection layer which is a SnO ₂ film. By the selective combustion layer, a specific gas is selectively burned, and the gas species reaching the gas detection layer is limited.
Therefore, when a low concentration volatile organic compound is present in the air, the volatile organic compound is highly sensitive due to a decrease in the electric resistance value of the gas detection layer within the predetermined elapsed time range after the start of energization driving. Can be detected.

[Configuration 2]
The gas detection device according to the present invention is, in addition to the configuration of the gas detection device of the above configuration 1, in addition to the configuration of the gas detection device of the above-described configuration 1, the sensor element includes the heater layer by the energization driving unit. The response time from the start of energization driving to the temperature of the gas detection layer becomes the high temperature state is configured to be 50 milliseconds or less,
After the start of energization driving to the heater layer by the energization driving means, the detection unit uses the electric resistance value of the gas detection layer within an elapsed time range of 20 milliseconds or more and 200 milliseconds or less, and the volatile organic It is configured to detect a compound.

Further, the gas detection method according to the present invention is suitably executed by the gas detection device having the above-described configuration 2, and as described in claim 8 in the column of the claims, the gas detection method having the above-described configuration 1 In addition to the configuration, the sensor element is configured such that the response time from the start of energization driving to the heater layer to the temperature of the gas detection layer being in the high temperature state is 50 milliseconds or less,
The volatile organic compound is detected using the electric resistance value of the gas detection layer within an elapsed time range of 20 milliseconds or more and 200 milliseconds or less after the start of energization driving to the heater layer. .

[Function and effect]
As described above, the reason why the detection sensitivity of the gas detection layer is significantly obtained for the volatile organic compound within the predetermined elapsed time range from the start of the energization drive to the heater layer is that the sensor element is in a low temperature state. The adsorbed volatile organic compound is desorbed from the sensor element by starting energization driving to the heater layer and shifting to a high temperature state, and further, the desorbed volatile organic compound within the predetermined elapsed time range. This is presumably because the concentration of the volatile organic compound near the gas detection layer temporarily increases because the organic compound stays in the vicinity of the gas detection layer.

  Accordingly, the response time from the start of energization driving to the heater layer by the energization driving means until the temperature of the gas detection layer reaches the high temperature state due to the large heat capacity of the sensor element or the heating amount of the heater layer is small. If it is relatively long, the volatile organic compound is gradually desorbed from the sensor element, and the temporary increase in concentration of the volatile organic compound is extremely small in the vicinity of the gas detection layer. Can no longer be detected.

  Therefore, according to the gas detection device and the gas detection method of configuration 2 above, the response time from the start of energization driving to the heater layer by the energization driving means until the temperature of the gas detection layer reaches a high temperature state is 50 milliseconds or less. Thus, by configuring the sensor element, the volatile organic substance is removed from the sensor element within an elapsed time range from the time 20 milliseconds after the start of energization driving to the heater layer to the time 200 milliseconds after the start of energization driving. The instantaneous desorption of the compound can cause a significant increase in the concentration of volatile organic compounds in the vicinity of the gas detection layer, which is good as a decrease in the electrical resistance of the gas detection layer. Therefore, even a low concentration volatile organic compound can be detected with high sensitivity.

  Furthermore, by starting the energization drive to the heater layer as described above and instantaneously shifting to a high temperature state, a significant increase in concentration occurs due to the volatile organic compound instantaneously desorbed from the sensor element in the vicinity of the gas detection layer. Thus, when detecting a volatile organic compound, it is preferable that a sufficient volatile organic compound is adsorbed on the sensor element in a low temperature state before shifting to a high temperature state. Therefore, the energization driving means starts the energization drive to the heater layer after setting the temperature of the gas detection layer to a low temperature state for, for example, 5 seconds or more, and sets the temperature of the gas detection layer to a high temperature state. It is preferable to configure.

[Configuration 3]
In the gas detection device according to the present invention, as described in claim 3 in the column of the claims, in addition to the configuration of the gas detection device of the above configuration 2, the energization driving means supplies the energization to the heater layer. After the drive is stopped and the temperature of the gas detection layer is set to the low temperature state, the energization drive to the heater layer is started to set the temperature of the gas detection layer to the high temperature state, and the volatile organic compound is reused. It is preferable to perform detection.
Further, the gas detection method according to the present invention is suitably executed by the gas detection device having the above-described configuration 3, and as described in claim 9 in the column of the claims, the gas detection method having the above-described configuration 2 In addition to the configuration, the energization driving means is used to stop the energization drive to the heater layer and set the temperature of the gas detection layer to the low temperature state, and then start energization drive to the heater layer. It is preferable to detect the volatile organic compound again with the temperature of the gas detection layer set to the high temperature state.
By starting energization driving to the heater layer as described above and instantaneously shifting to a high temperature state, a significant increase in concentration is caused by the volatile organic compound instantaneously desorbed from the sensor element in the vicinity of the gas detection layer. When detecting a volatile organic compound, it is preferable that a sufficient volatile organic compound is adsorbed on the sensor element in a low temperature state before shifting to a high temperature state. That is, it is desired that a sufficient volatile organic compound is adsorbed on the sensor element (gas detection layer) in the low temperature state before the transition to the high temperature state. Therefore, the energization driving means starts the energization drive to the heater layer after setting the temperature of the gas detection layer to a low temperature state for, for example, 5 seconds or more, and sets the temperature of the gas detection layer to a high temperature state. It is preferable to configure.

[Configuration 4]
In the gas detection device according to the present invention, as described in claim 4 of the column of claims, in addition to the configuration of any of the gas detection devices of the above configurations 1 to 3, the selective combustion layer is made of Pt. And a Pd catalyst are preferably supported.
In addition, the gas detection method according to the present invention is suitably executed by the gas detection device having the above-described configuration 4, and as described in claim 10 in the claims section, any one of the above-described configurations 1 to 3 can be used. In addition to the configuration of the gas detection method, the selective combustion layer preferably carries Pt and Pd catalysts.
In the sensor element, a selective combustion layer carrying Pt and Pd catalysts is formed on the surface of the gas detection layer which is a SnO ₂ film. The selective combustion layer burns the gas burned by the Pt and Pd catalysts, and limits the gas species that reach the gas detection layer.

[Configuration 5]
In the gas detection device according to the present invention, as described in claim 5 in the column of claims, in addition to the configuration of any of the gas detection devices according to the first to fourth configurations, the heater layer includes the diaphragm. It is preferably formed on the entire surface of the support substrate having the structure.

[Configuration 6]
In the gas detection device according to the present invention, as described in claim 6 of the column of the claims, in addition to the configuration of the gas detection device of any one of the above configurations 1 to 5, the volatile organic compound is It is preferably any one selected from the group consisting of ethanol, formaldehyde, acetaldehyde, acetone, toluene, xylene, chloroform and paradichlorobenzene.
Further, the gas detection method according to the present invention is suitably executed by the gas detection device having the above-described configuration 6, and as described in claim 11 in the column of claims, any one of the above-described configurations 1 to 4 can be used. In addition to the configuration of the gas detection method, the volatile organic compound may be any one selected from the group consisting of ethanol, formaldehyde, acetaldehyde, acetone, toluene, xylene, chloroform and paradichlorobenzene. preferable.

  Hereinafter, embodiments of the gas detection device according to the present invention will be described in detail.

[Sensor element]
FIG. 1 shows a structure of a thin film sensor element 20 used in the embodiment of the present invention.
The sensor element 20 is electrically connected with the presence or absence of a detection target gas on a support substrate having a diaphragm structure in which an outer peripheral part or both ends of a thin film-like support layer 5 (an example of a support film) are supported by a Si substrate 1 (support member). A film-like oxide gas detection layer 10 having a variable resistance value and a heater layer 7 (electric heating element) for heating the gas detection layer 10 are formed.

Next, a method for manufacturing the sensor element 20 will be described.
On the surface of the Si substrate 1 having the thermal oxide film 2 formed at 300 nm on both sides, the SiN film 3 and the SiO ₂ film 4 that will become the support layer 5 of the diaphragm structure are sequentially formed by plasma CVD to 150 nm and 1 μm, respectively.

Next, a heater layer 7 made of a PtW film is formed on the support layer 5 by 0.5 μm, and a heater pattern is formed by wet etching.
Then, an insulating layer 8 made of a SiO ₂ insulating film is formed on the heater layer 7 by a sputtering method with a thickness of 2.0 μm. Further, a junction between the heater layer 7 and an electrode 9 described later is etched with HF to open a window. Dawn.

Next, a Pt / Ta (200 nm / 50 nm) film is formed as the electrode 11 of the gas detection layer 10, and is patterned by wet etching. Here, Ta serves as a bonding layer between the SiO ₂ and Pt films.

Further, an SnO ₂ film as a gas detection layer 10 is formed as a gas detection layer 10 on the insulating layer 8 and the electrode 11 by a sputtering method to a thickness of 0.1 to 10 μm by a lift-off method.
Next, a powder having 7.5% by weight of Pt and Pd catalyst supported on alumina particles is used as a paste together with a binder, and is applied to the surface of the SnO ₂ film as the gas detection layer 10 by screen printing, and then fired. The selective combustion layer 12 having a thickness of about 30 μm is formed. Finally, Si is completely removed from the back surface of the substrate by dry etching to a diameter of 400 μm (diaphragm diameter) to obtain a diaphragm structure.

[Gas detection method]
Next, the gas detection method in the gas detection apparatus of this invention is demonstrated based on drawing.
As shown in FIG. 1, the gas detection device includes an energization driving means 30 for energizing and driving the heater layer 7 via the electrode 9 so that the temperature of the gas detection layer 10 changes from a low temperature state to a high temperature state, and a gas Detection that detects the electric resistance value of the gas detection layer 10 when the temperature of the detection layer 10 is changed to a high temperature state via the electrode 11 and detects the presence or absence as a detection target gas based on the detected electric resistance value. A portion 32 is provided.

  Further, the detection target gas is, for example, ethanol as the volatile organic compound, and the detection unit 32 starts the energization driving to the heater layer 7 by the energization driving means 30, and then the detection sensitivity of the gas detection layer 10 with respect to the volatile organic compound. The volatile organic compound is detected using the electrical resistance value of the film-like oxide within a predetermined elapsed time range in which is significantly obtained.

Specifically, the energization driving means 30 stops the energization driving of the heater layer 7 to bring the gas detection layer 10 to room temperature (low temperature), and the energization driving of the heater layer 7 to perform the gas detection layer 10. It is configured to repeatedly perform a high temperature state of heating to a predetermined temperature.
Furthermore, the time for stopping energization driving of the heater layer 7 (hereinafter referred to as heater OFF time) and the time for performing energization driving of the heater layer 7 (hereinafter referred to as heater ON time) are arbitrary. Can be set to a time.

  Further, as shown in FIG. 2, immediately after the energization driving to the heater layer 7 is started to shift from the low temperature state to the high temperature state, the electric resistance value of the gas detection layer 10 is ethanol as a volatile organic compound. Is significantly reduced, and the detection sensitivity of the gas detection layer 10 is significantly obtained with respect to the volatile organic compound within a predetermined elapsed time range after the start of energization driving to the heater layer 7.

Therefore, the detection unit 32 detects the electric resistance value of the gas detection layer 10 within a predetermined elapsed time range after the energization driving unit 30 starts energization driving of the heater layer 7 in order to detect the volatile organic compound. It detects and the presence of a volatile organic compound is detected as a decrease in its electrical resistance value.
In the graph of FIG. 2, the ON time is changed by setting the sum of the heater ON time and the heater OFF time to 30 seconds, and the electrical resistance value of the gas detection layer 10 measured at the end of the ON time and the elapsed time are the ON time. It shows the relationship with time.

  The reason why the detection sensitivity of the gas detection layer 10 is significantly obtained with respect to the volatile organic compound within a predetermined elapsed time range from the start of the energization driving to the heater layer 7 is that the sensor is in a low temperature state. The volatile organic compound adsorbed on the element 20 starts to be energized to the heater layer 7 and shifts to a high temperature state, so that it is desorbed from the sensor element 20 and further desorbed within a predetermined elapsed time range. This is probably because the separated volatile organic compound stays in the vicinity of the gas detection layer 10, so that the concentration of the volatile organic compound in the vicinity of the gas detection layer 10 temporarily increases.

  In view of this, the present gas detection device performs desorption of the volatile organic compound from the sensor element 10 as described above as quickly as possible, and effectively generates a temporary increase in the concentration of the volatile organic compound. The response time from the start of energization driving to the heater layer 7 by the energization driving means 30 until the temperature of the gas detection layer 10 reaches a high temperature state is 50 milliseconds or less. .

Specifically, as shown in FIG. 3, the temperature of the gas detection layer 10 is set when the set temperature of the gas detection layer 10 in a high temperature state is 450 ° C. and the elapsed time from the start of energization driving is about 30 msec. The sensor element unit 20 is configured so that the temperature of the gas detection layer 10 becomes the set temperature when the temperature is about 90% and the elapsed time is about 50 msec. The response time of the sensor element 20 is 50 msec from the start of energization driving until the temperature of the gas detection layer 10 reaches the set temperature.
At this time, the heat capacity of the sensor element 20 was about 2.3 pico J / K.

  Furthermore, when the sensor element 20 is configured so that the response time is 50 msec or less as described above, as shown in FIG. 2, 20 mm after the start of energization driving to the heater layer 7 by the energization driving means 30. It can be seen that the electric resistance value of the gas detection layer 10 within the elapsed time range of not less than 2 seconds and not more than 200 milliseconds greatly decreases when a volatile organic compound is present. Therefore, the detection part 32 can detect a volatile organic compound with high sensitivity using the electrical resistance value of the gas detection layer 10 within this elapsed time range.

  Furthermore, it is desired that a sufficient volatile organic compound is adsorbed on the sensor element 20 in a low temperature state before shifting to a high temperature state. Therefore, the energization drive means 30 of the present gas detection apparatus starts the energization drive to the heater layer 7 after setting the temperature of the gas detection layer 10 to a low temperature state for, for example, 5 seconds or more, and increases the temperature of the gas detection layer 10 to a high temperature. It is configured to be in a state. That is, the energization driving unit 30 sets the heater OFF time to 5 seconds or more.

That is, as shown in FIG. 4, if the heater OFF time is 5 seconds or more, a decrease in the electric resistance value of the gas detection layer 10 immediately after starting the energization drive to the heater layer 7 can be obtained, but the heater OFF If the time is less than 5 seconds, it is difficult to detect because the decrease in the electric resistance value is small. In particular, when detecting ethanol as a minute volatile organic compound, it is preferable to take this OFF time as long as possible. .
The graph of FIG. 4 shows the relationship between the electrical resistance value of the gas detection layer 10 measured at the end of the 50 msec ON time and the OFF time.

[Contrast between Example and Comparative Example]
Next, a comparison between an example in which ethanol as a volatile organic compound was detected by the gas detection device according to the present invention and a comparative example in which ethanol as a volatile organic compound was detected by a conventional gas detection device. The results will be described.

First, the gas detection device in the example includes the sensor element 20 similar to that of the embodiment of the gas detection device described so far, and further, the energization driving means 30 is a heater for bringing the gas detection layer 10 into a low temperature state. The heater ON time during which the OFF time is 29.95 sec and the gas detection layer 10 is in a high temperature state is 50 msec, and the heater layer 17 is repeatedly energized and not energized. The electrical resistance value of the gas detection layer 10 at the end (that is, when 50 msec has elapsed after starting the energization driving of the heater layer 7) is detected.
On the other hand, the gas detection device in the comparative example includes the sensor element 20 similar to that in the embodiment, and further, the heater layer 7 is always energized to keep the gas detection layer 10 in a constantly high temperature state. Configured to detect values.

In Examples and Comparative Examples, the electrical resistance value of the gas detection layer 10 when only air was supplied and ethanol (volatile organic compound) having a concentration of 0.1 to 100 ppm were supplied to the sensor element 20. The respective electric resistance values of the gas detection layer 10 are shown in FIGS. 5 and 6, respectively.
5 and 6, the electric resistance value of the gas detection layer 10 when only air is supplied is described at the point where the ethanol concentration is 0.02 ppm. Is not included.

As a result, in the gas detection device of the example, as shown in FIG. 5, even when ethanol with an ultra-low concentration of 0.1 ppm was supplied, the electric resistance value of the gas detection layer 10 was greatly reduced, It was confirmed that the presence of ethanol can be detected with high accuracy.
On the other hand, in the gas detection device of the comparative example, as shown in FIG. 6, unlike the example, even if ethanol is supplied, the electric resistance value of the gas detection layer 10 hardly decreases, so that ethanol is detected. It was confirmed that this was difficult.
Therefore, the gas detection device according to the present invention detects gas in a predetermined elapsed time range after the start of energization driving when ethanol, which is representative of a low concentration volatile organic compound, is present in the air. It can be said that it can be detected with high sensitivity due to a decrease in the electric resistance value of the layer 10.

Schematic showing the structure of the gas detector A graph showing the relationship between the electrical resistance value of the gas detection layer and the elapsed time Graph showing the temperature rise state of the gas detection layer The graph which shows the relationship between the electrical resistance value of a gas detection layer, and heater OFF time The graph which shows the ethanol detection result by the gas detection apparatus of an Example The graph which shows the ethanol detection result by the gas detection apparatus of a comparative example

Explanation of symbols

1: Si substrate (support member)
3: SiN film 4: SiO ₂ film 5: Support layer (an example of a support film)
7: Heater layer (electric heating element)
8: Insulating layer 9: Electrode of heater layer 10: Gas detection layer (film oxide)
11: Electrode 20 of gas detection layer: Sensor element 30: Energization drive means 32: Detection part

Claims (11)

A SnO ₂ film as a gas detection layer is formed on a support substrate having a diaphragm structure in which the outer peripheral portion or both ends of the thin film support film are supported by a support member, and the selective combustion layer is a surface of the gas detection layer. A sensor element comprising a heater layer for heating the gas detection layer,
Energization driving means for energizing and driving the heater layer so that the temperature of the gas detection layer changes from a low temperature state to a high temperature state;
Based on the electrical resistance value of the gas detection layer when the temperature of the gas detection layer is changed to a high temperature state, and a detection unit that detects the presence or absence of a volatile organic compound as a detection target gas,
After the start of energization driving to the heater layer by the energization driving means, the detection unit is within a predetermined elapsed time range in which the detection sensitivity of the gas detection layer with respect to the volatile organic compound is significantly obtained with respect to air. A gas detection device that detects the volatile organic compound using an electric resistance value of a gas detection layer. The sensor element is configured such that the response time from the start of energization driving to the heater layer by the energization driving means until the temperature of the gas detection layer reaches the high temperature state is 50 milliseconds or less,
After the start of energization driving to the heater layer by the energization driving means, the detection unit uses the electric resistance value of the gas detection layer within an elapsed time range of 20 milliseconds or more and 200 milliseconds or less, and the volatile organic The gas detection apparatus according to claim 1, wherein the gas detection apparatus is configured to detect a compound.   The energization drive means stops energization drive to the heater layer and sets the temperature of the gas detection layer to the low temperature state, and then starts energization drive to the heater layer to set the temperature of the gas detection layer to the temperature. The gas detection device according to claim 2, wherein the volatile organic compound is detected again as a high temperature state.   The gas detection device according to any one of claims 1 to 3, wherein the selective combustion layer carries Pt and Pd catalysts.   The gas detector according to any one of claims 1 to 4, wherein the heater layer is formed on an entire surface of the support substrate having the diaphragm structure.   The gas detection according to any one of claims 1 to 5, wherein the volatile organic compound is any one selected from the group consisting of ethanol, formaldehyde, acetaldehyde, acetone, toluene, xylene, chloroform and paradichlorobenzene. apparatus. A SnO ₂ film as a gas detection layer is formed on a support substrate having a diaphragm structure in which the outer peripheral portion or both ends of the thin film support film are supported by a support member, and the selective combustion layer is a surface of the gas detection layer. Using a sensor element comprising a heater layer that heats the gas detection layer,
The temperature of the gas detection layer is changed from a low temperature state to a high temperature state by energization driving means for energizing and driving the heater layer,
The electric resistance value of the gas detection layer when the temperature of the gas detection layer is changed to a high temperature state, and the gas detection layer with respect to the volatile organic compound as the detection target gas after the start of energization driving to the heater layer The gas detection method which detects the said volatile organic compound using the electrical resistance value of the gas detection layer in the predetermined elapsed time range in which the detection sensitivity of this is significantly obtained with respect to air. The sensor element is configured to have a response time of 50 milliseconds or less from the start of energization driving to the heater layer until the temperature of the gas detection layer reaches the high temperature state,
The volatile organic compound is detected using an electric resistance value of the gas detection layer within an elapsed time range of 20 milliseconds or more and 200 milliseconds or less after the start of energization driving to the heater layer. Gas detection method.   Using the energization drive means, the energization drive to the heater layer is stopped to bring the temperature of the gas detection layer to the low temperature state, and then the energization drive to the heater layer is started to start the temperature of the gas detection layer. The gas detection method according to claim 8, wherein the volatile organic compound is detected again in a high temperature state.   The gas detection method according to any one of claims 7 to 9, wherein the selective combustion layer carries Pt and Pd catalysts.   The volatile organic compound according to any one of claims 7 to 10, wherein detection is performed as any one selected from the group consisting of ethanol, formaldehyde, acetaldehyde, acetone, toluene, xylene, chloroform, and paradichlorobenzene. Gas detection method.

Images