JP2003279517A - Apparatus and method for detection of gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas detection apparatus by which existence of a volatile organic compound gas such as ethyl alcohol, formaldehyde or the like in the air at a low concentration of several ppm to several ppb is detected with high sensitivity, and to provide a gas detection method. <P>SOLUTION: A dehumidifying part 20 used to dehumidify a gas to be detected containing a detection object gas (the volatile organic compound gas), a sensor S which is provided with a semiconductor-type gas sensor 5 changing its electrical resistance due to contact with the detection object gas and which is constituted so as to be capable of introducing the gas to be detected, and a detection part 8 used to detect the detection object gas contained in the gas to be detected on the basis of a change in the electrical resistance of the gas sensor 5, are installed. A temperature maintenance means by which an operating temperature of the gas sensor 5 is maintained in a temperature range lower than a high- temperature-side critical temperature at which a detection sensitivity with reference to the detection object gas is obtained significantly with reference to the air is installed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas detection device for detecting a gas of a volatile organic compound such as ethyl alcohol and formaldehyde (hereinafter referred to as a detection target gas) contained in a gas to be detected, and , A gas detection method.

[0002]

2. Description of the Related Art With the increasing airtightness of houses, the presence of trace amounts of gaseous organic compounds such as ethyl alcohol and formaldehyde in the air (corresponding to the gas to be detected) in the house has become a problem. . These are called volatile organic compounds, but even when they are present in the air as low concentration gas of several ppm to several ppb which is not felt by human nose (olfaction), it is not Living in a different atmosphere may harm the human body. Therefore, a gas detection device or method for detecting the presence of these trace amounts of volatile organic compounds in the gaseous state in the air is desired, but conventionally, the presence of such trace amounts of volatile organic compounds is desired. Was not always easy to detect with high sensitivity.

By the way, the group including the present inventors
Previously, as disclosed in Japanese Patent Application Laid-Open No. 11-64264, a detection target contained in air at a low concentration of several ppm order by dehumidifying a gas to be detected (specifically, air) to remove water vapor. We have developed a technology to detect gas (specifically, combustible gas such as methane) with high sensitivity. By the way,
In the technique described in this publication, the dehumidified air is brought into contact with a semiconductor-type gas sensor such as tin oxide maintained at an operating temperature of about 350 ° C. to 450 ° C., so that the concentration of methane gas contained in the air is high. Achieves detection sensitivity.

[0004]

However, in the technique described in the above publication, a gas of a volatile organic compound such as ethyl alcohol and formaldehyde is contained in the air by several pp.
The presence at a low concentration of m to several ppb could not be detected with high sensitivity.

Therefore, as a result of further intensive research, the present inventors have developed a technique capable of detecting the presence of the above-mentioned low-concentration volatile organic compound with high sensitivity. That is, an object of the present invention is to provide a gas detection device and a detection method thereof that are capable of detecting a low concentration gas of a volatile organic compound with high sensitivity.

[0006]

The gas detecting device according to the present invention is as described in claim 1 of the scope of claims.
A dehumidifying section for dehumidifying the gas to be detected containing the gas to be detected, and a semiconductor type gas sensor whose electric resistance changes due to contact with the gas to be detected are introduced, and the gas to be detected dehumidified by the dehumidifying section is introduced. A sensor unit configured as possible and a detection unit for detecting the gas to be detected contained in the gas to be detected based on a change in electric resistance of the semiconductor type gas sensor, the first of which is provided. Is characterized in that the gas to be detected is a gas of a volatile organic compound, and the operating temperature of the semiconductor-type gas sensor is the limit on the high temperature side where the detection sensitivity for the gas to be detected is significantly obtained with respect to air. The point is that the temperature maintaining means for maintaining the temperature range lower than the temperature is provided.

According to the second characteristic constitution, as described in claim 2, in addition to the first characteristic constitution, the temperature maintaining means makes the operating temperature of the semiconductor type gas sensor 0 ° C. to 220 ° C.
It is configured to be maintained in the range of ° C.

In the third characteristic constitution, as described in claim 3, in addition to the first or second characteristic constitution, the dehumidifying section sets the dew point of the gas to be detected to 0 ° C. or lower. It is a point that is configured.

In the fourth characteristic constitution, as described in claim 4, in addition to any one of the first to third characteristic constitutions, the gas to be detected is alcohols containing ethanol or methanol, formaldehyde. It is a gas contained in at least any one of aldehydes including acetaldehyde and ketones including acetone.

As described in claim 5, the gas detection method according to the present invention dehumidifies the gas to be detected containing the gas to be detected, and the dehumidified gas to be detected is contacted with the gas to be detected. By contacting the semiconductor type gas sensor whose electric resistance changes by the one for detecting the detection target gas contained in the gas to be detected based on the change in the electric resistance of the semiconductor type gas sensor, the detection target gas is Using a gas of a volatile organic compound, and maintaining the operating temperature of the semiconductor type gas sensor in a temperature range lower than a high temperature limit temperature at which the detection sensitivity for the gas to be detected is significantly obtained for air. It is a feature.

The operation and effect of the above characteristic structure will be described below. According to the first characteristic configuration of the gas detection apparatus according to the present invention, the detection target gas containing the gas of the volatile organic compound that is the detection target gas is dehumidified in the dehumidifying section, and the detection target gas is The operating temperature of the semiconductor gas sensor whose electrical resistance changes due to contact is maintained in a temperature range lower than the limit temperature on the high temperature side where the detection sensitivity to the detection target gas is significantly obtained for air by the temperature maintaining means,
The detection target gas dehumidified in the dehumidifying unit is introduced into the sensor unit including the semiconductor type gas sensor and brought into contact with the semiconductor type gas sensor, and the change in the electrical resistance of the semiconductor type gas sensor is changed by the contact with the gas to be detected. Based on the above, the detection unit detects the gas to be detected contained in the gas to be detected.

That is, the detection sensitivity of the semiconductor type gas sensor for the gas of low concentration volatile organic compound contained in the dehumidified gas to be detected changes depending on the operating temperature,
It cannot be obtained significantly for air in the operating temperature range higher than the high temperature limit temperature, but is significantly obtained for air in the operating temperature range lower than the high temperature side limit temperature. By maintaining the operating temperature of the gas sensor in a temperature range lower than the above-mentioned temperature limit on the high temperature side, it is possible to realize high gas detection sensitivity with respect to a gas of a volatile organic compound contained in the dehumidified gas to be detected. You can Therefore, a gas detection device capable of detecting a low-concentration volatile organic compound gas with high sensitivity is provided.

According to the second characteristic configuration, the operating temperature of the semiconductor type gas sensor is 0.degree.
It is maintained in the range of 220 ° C. That is, when the detection unit detects the gas to be detected in the gas to be detected based on the change in the electrical resistance of the semiconductor gas sensor, it is necessary to consider detection errors such as circuit errors and errors due to temperature and humidity fluctuations. As illustrated in FIG. 5, the electric resistance of the semiconductor-type gas sensor changes depending on the temperature, but when the resistance value of the semiconductor-type gas sensor exceeds 1 MΩ in the temperature range on the low temperature side, it becomes difficult to detect the resistance value. On the other hand, it is necessary that the temperature is 0 ° C. or higher. On the other hand, in the temperature range on the high temperature side, in order to be able to significantly detect the gas of the volatile organic compound with respect to air, the gas of the volatile organic compound must be Since it is desirable that the resistance value of the semiconductor type gas sensor changes more than twice as compared with the case where only air is used, it is 2
It is necessary to be 20 ° C or lower. That is, the limit temperature on the high temperature side becomes 220 ° C. Therefore, by maintaining the operating temperature of the semiconductor-type gas sensor in the range of 0 ° C. to 220 ° C., a preferable specific example of a gas detection device capable of detecting a gas of a low concentration volatile organic compound with high sensitivity. Embodiments are provided.

According to the third characteristic construction, the dehumidifying section dehumidifies the detected gas so that the dew point of the detected gas becomes 0 ° C. or lower. That is, when the detection unit detects the gas to be detected in the gas to be detected based on the change in the electric resistance of the semiconductor gas sensor, it is necessary to consider a detection error such as a circuit error and an error due to temperature and humidity fluctuation. As illustrated in FIG. 6, the electric resistance of the semiconductor type gas sensor becomes smaller as the dew point of the gas to be detected becomes lower, and the resistance value of the semiconductor type gas sensor becomes smaller than 1 MΩ under the condition that the dew point is 0 ° C. or less. The dew point of the detection gas needs to be 0 ° C. or lower. Therefore, by setting the dew point of the gas to be detected to be 0 ° C. or lower, a preferable specific embodiment of the gas detection device capable of detecting the gas of the low concentration volatile organic compound with high sensitivity is provided. .

According to the fourth characteristic constitution, the gas contained in at least one of alcohols containing ethanol and methanol, aldehydes containing formaldehyde and acetaldehyde, and ketones containing acetone is used. , Is detected as the detection target gas. Therefore, a specific embodiment of a gas detection device capable of detecting typical alcohol gases, aldehyde gases, and ketone gases as the volatile organic compound gas with high sensitivity is provided.

According to the characteristic configuration of the gas detection method according to the present invention, the gas to be detected containing the gas of the volatile organic compound, which is the gas to be detected, is dehumidified and brought into contact with the gas to be detected to obtain an electrical resistance. Changes the operating temperature of the semiconductor-type gas sensor in a temperature range lower than the limit temperature on the high temperature side where the detection sensitivity for the detection target gas is significantly obtained for air, and the dehumidified detection target gas is used as the semiconductor. The gas to be detected contained in the gas to be detected is detected based on the change in the electrical resistance of the semiconductor gas sensor which is brought into contact with the gas sensor to be detected and changed due to the contact with the gas to be detected. That is, the detection sensitivity of the semiconductor gas sensor for the low concentration volatile organic compound gas contained in the dehumidified gas to be detected varies depending on the operating temperature, and the operating temperature range higher than the high temperature side limit temperature. However, since it can be obtained significantly for air in the operating temperature range lower than the above-mentioned high temperature side limit temperature, the operating temperature of the semiconductor type gas sensor should be higher than the above-mentioned high temperature side limit temperature. By maintaining the temperature range at a low temperature, it is possible to realize high gas detection sensitivity for the gas of the volatile organic compound contained in the dehumidified gas to be detected.
Therefore, a gas detection method capable of detecting a low-concentration volatile organic compound gas with high sensitivity is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a gas detection device and a gas detection method according to the present invention will be described with reference to the drawings. As shown in FIG. 1, a gas detection device 1 according to the present invention
The dehumidifying section 20 includes a dehumidifying section 20 for dehumidifying the gas to be detected containing the gas to be detected, and a semiconductor gas sensor 5 whose electric resistance changes due to contact with the gas to be detected.
And a detection unit for detecting the detection target gas contained in the detection target gas based on a change in electric resistance of the semiconductor type gas sensor 5 And a section 8 are provided. A signal line 7 connects the semiconductor gas sensor 5 and the detector 8.

The gas to be detected is a gas of a volatile organic compound, and specifically, of alcohols containing ethanol and methanol, aldehydes containing formaldehyde and acetaldehyde, and ketones containing acetone. It is a gas contained in at least one of the classes. Note that these gases are combustible gases.

The sensor section S is provided with a sensor chamber 2 into which a gas to be detected is introduced. The semiconductor type gas sensor 5 is installed in the sensor chamber 2 and the gas to be detected is supplied to the sensor chamber 2. A suction pump 3 for sucking the gas to be detected and the dehumidifying section 20 are provided in the introduction path 4 for introducing the gas.

FIG. 2 shows the detailed structure of the dehumidifying section 20. The dehumidifying section 20 discharges water vapor in the gas to be detected to the outside of the introduction path 4 and allows the gas to be detected to flow into the sensor chamber 2. Specifically, the plurality of hollow fibers 21 are provided, and the gas to be detected introduced from the gas to be detected inlet 22 into the plurality of hollow fibers 21 is guided to the gas to be detected outlet 23. On the other hand, the dehumidified gas to be detected is introduced into the outer space of the hollow fiber 21 through the purge gas supply path 25 while adjusting the pressure, and is discharged from the purge gas outlet 26 to the outside. Here, the hollow fiber 21 is made of a fluororesin having a water vapor selective permeation function, allows the permeation of water vapor between the inside and outside of the fiber, and suppresses the permeation of oxygen, nitrogen and the above-mentioned gas to be detected. Therefore, the water vapor in the detected gas moves to the purge gas side, and the detected gas is dehumidified. Then, the dehumidifying unit 20 is configured to adjust the dew point of the gas to be detected sent to the sensor chamber 2 to 0 ° C. or lower by adjusting the pressure of the purge gas.

FIG. 3 shows the basic structure of a thin film type sensor used as an example of the semiconductor type gas sensor 5 and the structure of the detection section 8. In the above sensor, a gas detection layer 6 made of a thin film of an oxide semiconductor (specifically, tin oxide which is an n-type semiconductor) is formed on a silicon wafer substrate 10, and a pair of platinum comb-shaped thin films are formed on the gas detection layer 6. The electrode 11 is formed. Further, a thin film heater 12 for heating is formed on the back surface side of the substrate 10.

The film thickness of the gas detection layer 6 is 20 μm or less,
It is preferably about 10 μm or less. This thin film is formed, for example, by heating the silicon wafer substrate 10 at 1000 ° C. for 2 hours in an atmosphere containing oxygen and water vapor to form SiO ₂ on the surface.
After forming the insulating layer, it can be obtained by a vapor deposition operation using a parallel plate type high frequency magnetron sputtering device and a SnO ₂ sintered body as a target material. As the semiconductor type gas sensor 5, other than the above thin film type,
A sintered type using an alumina material may be used.

The terminals of the thin film heater 12 are connected to a heating power source 13. The operating temperature of the semiconductor gas sensor 5 can be maintained in the range of room temperature to 220 ° C. by adjusting the voltage and current of the heating power supply 13.

The detector 8 will be described. The pair of platinum comb-shaped thin film electrodes 11 are connected to the load resistance 14 by the signal line 7.
And a power source 15 for detection are connected in series, and the voltage appearing between the terminals 9 of the load resistor 14 is determined by a discrimination circuit 16 such as a microcomputer.
Has been entered in. That is, a voltage applied from the detection power supply 15 is applied across the terminals 9 of the load resistor 14 to the load resistor 1.
4 and the resistance of the gas detection layer 6 between the electrodes 11 appear, and since the resistance value of the load resistor 14 and the voltage value of the detection power supply 15 are fixed values, the voltage between the terminals 9 is increased. The determination circuit 16 can determine the resistance value of the gas detection layer 6 (the resistance value of the semiconductor-type gas sensor 5) from the voltage.
In addition to the above circuit, a pair of platinum comb thin-film electrodes 11 may be incorporated in the Wheatstone bridge to obtain the resistance value of the gas detection layer 6.

Next, the gas detection characteristics of the gas detection device 1 having the above structure will be described. In FIG. 4, the operating temperature of the semiconductor type gas sensor 5 is maintained at 150 ° C. and the dew point of the gas to be detected (air) is lowered to -20 ° C., in the absence of gas (only air) and in air. Ethyl alcohol, formaldehyde, hydrogen,
The result of having measured the resistance value of the gas sensor 5 when each gas of methane exists in the low concentration condition of 0.05-10 ppm is shown. Here, in order to accurately detect the gas concentration, in consideration of the measurement error (measurement limit) due to the circuit noise in the detection unit 8 and the fluctuation of temperature and humidity, the sensor resistance value is 1 MΩ or less, and the gas Should be sufficiently low (at least twice as much difference) as in the absence of.

In the above measurement data, the resistance value of the gas sensor 5 in the absence of gas exceeds 10 MΩ, and for ethyl alcohol and formaldehyde, the sensor resistance value is 1 from the low concentration of 0.05 ppm.
Since it is less than MΩ, it can be detected with extremely high sensitivity.
On the other hand, with respect to hydrogen, when the amount is less than 1 ppm, the sensor resistance value is 10 MΩ or more, and even in the range of 1 to 10 ppm, it is 1 MΩ or more, and accurate detection is impossible. Furthermore, with respect to methane, if it is less than 10 ppm, it is always 10 MΩ or more, and detection is impossible. Therefore, the semiconductor-type gas sensor 5 of the present embodiment can be used for trace amounts of gases of volatile organic compounds such as ethyl alcohol and formaldehyde.
Specific high sensitivity is realized.

In FIG. 5, the operating temperature of the semiconductor type gas sensor 5 is changed in a state where the dew point of the gas to be detected (air) is -20.degree. C., and only when air is used and when ethyl is used as a gas to be detected in the air. The result of having measured the resistance value of the gas sensor 5 when alcohol exists in 0.05 ppm concentration conditions is shown. Regarding the operating temperature on the high temperature side, when the temperature is 220 ° C. or lower, the sensor resistance value in the case of only air is 1 MΩ or more, whereas the sensor resistance value in the presence of 0.05 ppm ethyl alcohol is 1 MΩ or less, and Since the ratio of the sensor resistance values of the two is about 2 (the sensor resistance value in the presence of ethyl alcohol is about 1/2 or less of the resistance value in the case of only air), it is possible to detect ethyl alcohol with high sensitivity. It is possible. At operating temperatures above 220 ° C., the ratio of sensor resistance values in the case of air alone and in the presence of ethyl alcohol is less than double, making detection of ethyl alcohol difficult. It should be noted that the sensor resistance value in the presence of ethyl alcohol is the lowest around 150 ° C., which indicates that this temperature is optimal for gas detection.

Therefore, by the thin film heater 12 and the heating power source 13, the operating temperature of the semiconductor type gas sensor 5 is higher than the limit temperature on the high temperature side where the detection sensitivity for the gas to be detected is significantly obtained for air. Temperature maintaining means H for maintaining a low temperature range is configured. In this embodiment, the high temperature side limit temperature is 220 ° C. as described above.

On the other hand, with respect to the operating temperature on the low temperature side, at 0 ° C. or lower, the sensor resistance value in the presence of 0.05 ppm of ethyl alcohol becomes 1 MΩ or higher, so that ethyl alcohol cannot be detected. Therefore, in the gas detection device 1, the operating temperature of the semiconductor type gas sensor 5 is set to 0 ° C to 220 ° C.
It is desirable to maintain the range. In this embodiment, under low temperature conditions where the room temperature is lower than 0 ° C. (for example, in a commercial refrigerator), the thin film heater 12 causes the operating temperature of the semiconductor gas sensor 5 to be 0 ° C. or higher. So that the low concentration gas of the volatile organic compound can be detected.

In FIG. 6, the operating temperature of the semiconductor type gas sensor 5 is maintained at 150 ° C., the dew point of the gas to be detected (air) is changed, and when no gas is present, ethyl alcohol is used as a gas to be detected in the air. Shows the result of measuring the resistance value of the gas sensor 5 in the case where is present in a low concentration condition of 0.05 ppm. The sensor resistance value is 1 when the dew point is 0 ° C or less.
It becomes less than MΩ and ethyl alcohol can be detected. Therefore, therefore, the dehumidifying section 20 is configured to set the dew point of the gas to be detected (air) to 0 ° C. or lower.

Next, the gas detection method according to the present invention dehumidifies the gas to be detected containing the gas to be detected, and changes the electric resistance of the dehumidified gas to be detected by contact with the gas to be detected. A gas detection method of contacting a semiconductor type gas sensor to detect the detection target gas contained in the detection target gas based on a change in electrical resistance of the semiconductor type gas sensor, wherein the detection target gas is a volatile organic gas. A compound gas, and the operating temperature of the semiconductor-type gas sensor is maintained in a temperature range lower than a limit temperature on the high temperature side at which the detection sensitivity for the gas to be detected is significantly obtained for air. . Although not described in detail, in the gas detection device, specific conditions such as the gas to be detected, the gas to be detected, the dew point of the gas to be detected after dehumidification, the structure of the semiconductor type gas sensor, and the operating temperature of the semiconductor type gas sensor are described. The same conditions as those described above are set.

Next, as described above, in the gas detecting apparatus and the gas detecting method according to the present invention, by dehumidifying the gas to be detected (air) and setting the operating temperature of the semiconductor type gas sensor 5, a low concentration volatilization is performed. The technical mechanism that can detect the gas of organic compounds with high sensitivity will be explained separately for sensitivity increase by dehumidification and temperature dependence. In the following description, the case where the gas to be detected is a combustible gas is described as an example, and the gas detection layer 6 of the semiconductor type gas sensor 5 is called a gas sensitive body.

(Mechanism of Increased Sensitivity by Dehumidification) Generally, in a gas sensor for a combustible gas, the combustible gas is adsorbed on the surface of a gas-sensitive body such as tin oxide, or an interaction such as an oxidation reaction occurs, and the interaction thereof occurs. Detects flammable gas by causing a change in the resistance value of the gas sensitive body. On the other hand, since moisture in the air is also adsorbed by the gas-sensitive material, it causes a change in the resistance value of the gas-sensitive material, but the effect is smaller than that of the flammable gas, and dehumidification does not mean that the flammable gas and It cannot generally be said that body interactions are significantly greater. However, in the present invention, it is said that the sites on the gas-sensing body where gases such as alcohols such as ethanol and methanol, aldehydes such as formaldehyde and acetaldehyde, and ketones such as acetone are adsorbed are significantly activated by dehumidification. Conceivable. This is a site on the gas-sensing body where a general flammable gas such as hydrogen is adsorbed / reacted with the above alcohols, aldehydes,
The parts on the gas-sensitive body where the gases such as ketones are adsorbed / reacted are actually different, whereas the parts of the gas-sensitive body where the general flammable gas is adsorbed / reacted are less susceptible to moisture. Based on the new finding found in the process of the present invention that the sites on the gas-sensing body where the above-mentioned alcohols, aldehydes, ketones, etc., adsorb and react with gas are strongly affected by water and are inactivated. ing. Therefore, it is considered that the dehumidification remarkably increases the interaction between the gas such as alcohols, aldehydes, and ketones and the gas-sensitive material, thereby increasing the sensitivity. On the other hand, with a general combustible gas such as hydrogen, the adsorption / reaction site on the gas-sensitive body is unlikely to be affected by moisture, and therefore it is considered that desensitization has little effect of increasing sensitivity.

(Temperature Dependent Mechanism) The thermal activation action is also involved in the adsorption / reaction of the above-mentioned alcohols, aldehydes, ketones and the like on the gas-sensitive material. Therefore, by increasing the temperature from around 0 ° C., the thermal activation action becomes larger. However, if the temperature is higher than 150 ° C., the adsorption on the gas-sensitive body becomes difficult to occur, and even if it is adsorbed, it is burned and removed before the interaction causing the resistance change of the gas-sensitive body. It is considered that the probability is increased, and as a result, the effect of increasing the sensitivity is reduced.

[Other Embodiment] Another embodiment will be described below. In the above embodiment, the gas of the volatile organic compound that is the detection target gas is at least one of alcohols containing ethanol and methanol, aldehydes containing formaldehyde and acetaldehyde, and ketones containing acetone. The gas included in the class,
Other volatile organic compound gases may be used. Also,
In the above embodiment, the gas to be detected containing the gas to be detected is air, but a gas other than air may be used.

In the above embodiment, the semiconductor type gas sensor 5 is used.
Although the oxide semiconductor which is the main component of the gas detection layer 6 is composed of an n-type semiconductor (specifically, tin oxide), it may be composed of another n-type semiconductor or a p-type semiconductor. When the oxide semiconductor, which is the main component of the gas detection layer 6, is changed, the temperature condition maintained by the temperature maintaining means H (high temperature side limit temperature, etc.) is changed to an appropriate value. .

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a gas detection device according to the present invention.

FIG. 2 is a side sectional view showing a structure of a dehumidifying section.

FIG. 3 is a diagram showing a structure of a thin film type semiconductor type gas sensor and a detection circuit.

FIG. 4 is a graph showing a relationship between a gas concentration and a sensor resistance value in a low gas concentration region.

FIG. 5 is a graph showing the relationship between sensor temperature and sensor resistance value.

FIG. 6 is a graph showing the relationship between the dew point of the gas to be detected and the sensor resistance value.

[Explanation of symbols]

5 Semiconductor type gas sensor 8 detector 20 Dehumidification section H temperature maintaining means S sensor section

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsumi Higaki             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Within Osaka Gas Co., Ltd. (72) Inventor Hirokazu Sasaki             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Within Osaka Gas Co., Ltd. (72) Inventor Hisao Onishi             4-1-2 Hirano-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Within Osaka Gas Co., Ltd. (72) Inventor Shinichi Ochi             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Takuya Suzuki             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 2G046 AA18 AA24 AA25 AA26 DB05                       EB06

Claims (5)

[Claims] 1. A dehumidifying section for dehumidifying a gas to be detected containing a gas to be detected, and a semiconductor-type gas sensor whose electric resistance changes due to contact with the gas to be detected, and dehumidified by the dehumidifying section. A gas detection device provided with a sensor part configured to be able to introduce a gas to be detected, and a detection part for detecting the gas to be detected contained in the gas to be detected based on a change in electric resistance of the semiconductor gas sensor. The detection target gas is a gas of a volatile organic compound, and the operating temperature of the semiconductor-type gas sensor, the detection temperature for the detection target gas detection temperature significantly high temperature limit temperature on the side A gas detection device provided with temperature maintaining means for maintaining a temperature range lower than the temperature range. 2. The gas detector according to claim 1, wherein the temperature maintaining means is configured to maintain the operating temperature of the semiconductor type gas sensor within a range of 0 ° C. to 220 ° C. 3. The gas detection device according to claim 1, wherein the dehumidifying section is configured to set a dew point of the gas to be detected to 0 ° C. or lower. 4. The gas to be detected is a gas contained in at least one of alcohols containing ethanol and methanol, aldehydes containing formaldehyde and acetaldehyde, and ketones containing acetone. Item 4. The gas detection device according to any one of items 1 to 3. 5. A semiconductor type gas sensor whose electric resistance changes by dehumidifying a gas to be detected containing a gas to be detected, the dehumidified gas to be detected being brought into contact with the gas to be detected, A gas detection method for detecting the detection target gas contained in the detection target gas based on a change in electric resistance of a gas sensor, wherein the detection target gas is a volatile organic compound gas, and the semiconductor A gas detecting method, wherein the operating temperature of the type gas sensor is maintained in a temperature range lower than a limit temperature on the high temperature side where the detection sensitivity for the gas to be detected is significantly obtained for air.