TW201522958A - Environmental monitoring system - Google Patents

Abstract

An environment monitoring system (Z) provided with a gas detection unit (A) for detecting gas components present in the interior of a closed space, wherein the gas detection unit (A) is provided with multiple gas detection means (10, 20) provided to different regions in the closed space. The environment monitoring system (Z) is also provided with an analysis unit (E) for analyzing, when one of the gas detection means (10, 20) detects a detection value having a predetermined value or higher, the gas components contained in the atmosphere in the periphery of the gas detection means (10, 20) that detected the detection value having the predetermined value or higher.

Description

Environmental monitoring system

The present invention relates to an environmental monitoring system including a gas sensing unit that senses a gas component existing inside a closed space.

For example, in a semiconductor manufacturing plant or the like, there is a device for removing a dry solvent from a product or an organic solvent component contained in a small amount in a drain, and such a device may have a volatile organic compound (VOC) gas which is an odor component. . The VOC gas contains, for example, formaldehyde, toluene, etc., which may cause irritation to eyes, nose, and throat.

The VOC gas system can be sensed using, for example, a gas sensing device having a semiconductor gas sensing element.

In the above, the gas sensing device including the semiconductor gas sensing element which is a conventional technique in the present invention is a general technique, and thus does not show a conventional technical document such as a patent document.

In the semiconductor manufacturing plant described above, alcohols (ethanol) for disinfection or cleaning are frequently used in a clean room in which the temperature and humidity are managed to circulate.

As described above, in a semiconductor manufacturing plant, a gas such as VOC gas or ethanol floats in an ambient gas. For example, if a VOC gas is to be sensed by a gas sensing device, ethanol may be sensed as an obstruction gas. It is difficult to selectively sense the situation of VOC gas. In addition to the VOC gas, in order to sense a desired sensed gas to be a target, ethanol is also sensed as a hindrance gas, and there is a problem that the sensed gas cannot be accurately sensed.

Accordingly, it is an object of the present invention to provide an environmental monitoring system that can identify a plurality of gas components.

An environmental monitoring system according to the present invention for achieving the above object is provided with an environmental monitoring system that senses a gas sensing unit that is present in a closed space, and is characterized in that the gas sensing unit is provided. A plurality of gas detecting means having a detection value equal to or greater than a predetermined value when a detected value of a predetermined value or more is detected by any one of the gas detecting means is provided in the plurality of regions of the closed space. An analysis unit that analyzes a gas component contained in the ambient gas around the detection means.

According to this configuration, when any of the gas detecting means detects a detection value equal to or greater than a predetermined value, it is possible to capture and detect the predetermined value or more. The ambient gas around the gas detecting means of the detected value is supplied to the analysis unit, and the type, concentration, and the like of the gas component are sensed and analyzed (identified).

As described above, when any of the gas detecting means detects a detection value equal to or greater than a predetermined value, the gas component contained in the ambient gas around the gas detecting means that detects the detection value equal to or greater than the predetermined value is analyzed. This can stipulate that the timing of the gas component is analyzed by the analysis unit. In other words, when any of the gas detecting means detects a detection value equal to or greater than a predetermined value, when the desired gas component is sensed, the analysis unit analyzes the ambient gas around the gas detecting means at this timing. Since the desired gas component is analyzed by the analysis unit, the analysis of the gas component can be performed in a reliable and detailed manner.

In a second aspect of the environmental monitoring system of the present invention, the gas sensing unit includes: a first gas detecting means and a second gas detecting means, wherein the sensing characteristics of the sensed gas are different between the two. The desired gas component is sensed, analyzed, and monitored based on the sensed output of the first gas detecting means and the sensed output of the second gas detecting means.

As shown in the present configuration, the first gas detecting means and the second gas detecting means are provided, and the sensing characteristics of the sensed gas are different in the two, whereby the gas corresponding to the characteristics of the respective detecting means can be sensed. ingredient.

For example, if the alcohol sensing sensitivity of the second gas detecting means is high, if the alcohol concentration is increased in the sensing target space, the first gas detecting is performed. The sensing output of the alcohol component is lower than that of the second gas detecting means, but the sensing output of the alcohol component by the second gas detecting means becomes high. At this time, if the output of the first gas detecting means is obtained to be larger than the predetermined sensing output, it can be recognized that the gas component other than the alcohol is sensed, and if the output of the second gas detecting means is obtained, the predetermined ratio is obtained. When the sensed output is a larger value, it can be recognized as an alcohol-sensing person, so that the alcohol, and other gas components can be simultaneously identified, sensed, analyzed, and monitored.

In other words, when it is desired to detect a gas component other than an alcohol, if an alcohol is present, the alcohol becomes an obstruction gas, and it is difficult to detect a gas component other than the alcohol. In this case, when a gas component other than the alcohol is detected in a state where the alcohol is removed by using a filter or the like, the running cost of the filter or the like increases. However, in the environmental monitoring system of the present invention, only two detection means (first gas detecting means and second gas detecting means) having different alcohol detection sensitivities can be provided, and alcohols and other gas components can be used. Simultaneous identification, analysis and monitoring can be used to construct an environmental monitoring system that is simple and cost-effective.

According to a third aspect of the environmental monitoring system of the present invention, the gas detecting means in the gas sensing unit sets a zero point using a clean gas. Further, since the state of the zero point is formed as an ideal state of the closed space, the zero point can be set to be formed as a target, and it is easy to understand how much the current state deviates from the ideal state.

Thereby, the zero point adjustment of the gas detecting means can be surely performed.

The fourth feature of the environmental monitoring system of the present invention is The monitoring unit includes: a monitoring unit that monitors a change in the gas component; and a collecting means that collects ambient gas around the gas detecting means, and sends the collected ambient gas to the analyzing unit, and any gas detecting means When the detection value of the predetermined value or more is detected, the monitoring unit instructs the collection means to capture the ambient gas around the gas detection means having a predetermined value or more, and instructs the analysis unit to analyze the detection means by the collection means. The ambient gas delivered.

According to this configuration, the monitoring unit can recognize the detected value of the gas detecting means, and control the desired gas detecting means to emit the ambient gas trapping command to the collecting means in accordance with the detected value. Further, the monitoring unit can control the analysis unit to issue an analysis command of the environmental gas after issuing the capture command. In other words, if the capture command or the analysis command can be executed in the monitoring unit, for example, when the monitoring unit is provided at any of the near or separated positions of the gas sensing unit, or When the monitoring unit is provided outside the closed space, the capture instruction or the analysis command can be executed at the desired timing.

A fifth feature of the environmental monitoring system of the present invention is that the first gas detecting means includes a noble metal wire; and the noble metal wire is covered, and a metal oxide semiconductor containing molybdenum oxide mainly containing tin oxide or indium oxide is used. a gas sensing portion formed; and a catalyst layer containing at least one selected from the group consisting of alumina, vermiculite, lanthanum aluminum oxide, and zeolite as a support on the outer peripheral side of the gas sensing portion The medium layer carries at least one of a tungsten oxide or a molybdenum oxide as the first semiconductor-type gas sensing element.

In the second embodiment (the main component of the metal oxide semiconductor is tin oxide) to be described later, and in the fifth embodiment (the main component of the metal oxide semiconductor is indium oxide), the semiconductor gas to which the molybdenum oxide is added to the gas sensing portion is used. The sensing elements (Inventive Examples 2 and 3) and the semiconductor type gas sensing elements (Comparative Examples 1 and 2) in which no molybdenum oxide was added to the gas sensing portion were examined for the sensing sensitivity of the odor component.

As a result, in the semiconductor-type gas sensing elements of Comparative Examples 1 and 2, no clear difference in gas sensitivity was observed between the odor component and the combustible gas (FIGS. 4 and 8). The semiconductor gas sensing element of 3 is considered to be sensitive to the sensing sensitivity of odor components such as ethanol, toluene, acetone, and ethyl acetate (Figs. 3 and 7).

Further, in Example 3 to be described later, in the inventive example 2 and the comparative example 1, the change in the gas sensitivity in the environment in which the polyoxygen gas was present was investigated.

As a result, in the semiconductor-type gas sensing element of Comparative Example 1, in particular, in the initial stage of the polyoxymethane gas exposure, the unstable gas sensitivity was exhibited (FIG. 6), whereas the semiconductor-type gas sensing element of the inventive example 2 was used. Even in the presence of polyoxyl gas, it was found to be stable (substantially certain) gas sensitivity (Fig. 5).

Therefore, the semiconductor-type gas sensing element of the present configuration can detect the odor component with high sensitivity by adding molybdenum oxide to the gas sensing portion, and can accurately detect the odor component in the presence of the polyoxygen gas.

In addition, it will be composed of alumina, vermiculite, lanthanum aluminum oxide, At least one of the selected zeolites as the carrier constitutes a catalyst layer, and when the catalyst layer carries at least one of a tungsten oxide or a molybdenum oxide, when the sensing target gas has an alcohol, It is also possible to suppress the sensitivity of the sensor to alcohols (see Example 12 and Fig. 12). That is, the alcohol that reaches the surface of the catalyst layer is decomposed by tungsten oxide or molybdenum oxide (referred to as an intramolecular dehydration reaction of an alcohol by an acid metal oxide).

This reaction (C ₂ H ₅ OH→C ₂ H ₄ +H ₂ O) occurs at a relatively high temperature (above 300 ° C). At this time, ethylene is generated, but the sensor of the present invention has a very low sensitivity to ethylene, so the sensor of the present invention has a very low sensitivity to alcohol.

Therefore, the semiconductor-type gas sensing element of the present configuration is formed so as to be sensitive to the odor component while suppressing the sensitivity to alcohol.

According to a sixth aspect of the environmental monitoring system of the present invention, the second gas detecting means is configured to include a catalyst layer in the first gas detecting means.

According to this configuration, the second gas detecting means can improve the sensitivity to the alcohol component as compared with the first gas detecting means.

A seventh feature of the environmental monitoring system of the present invention is that at least one of a cerium oxide and a lead oxide is added to the metal oxide semiconductor.

According to this configuration, at least one of a cerium oxide and a lead oxide is added to the metal oxide semiconductor portion, whereby it is possible to obtain high sensitivity with respect to, for example, toluene or acetone belonging to an odor component, and to hydrogen, methane, Among the other gases such as ethylene, the semiconductor gas sensing element is excellent.

A‧‧‧Gas Sensing Department

B‧‧‧ Computing Department

C‧‧‧Notification Department

D‧‧‧Display Department

E‧‧‧Analysis Department

F‧‧‧Monitor Department

R0, R1, R2‧‧‧ fixed resistor

X‧‧‧First semiconductor gas sensing element

X’‧‧‧Second semiconductor gas sensing element

Z‧‧‧Environmental Monitoring System

1‧‧‧ precious metal wire

2‧‧‧Gas sensing department

3‧‧‧ catalyst layer

10‧‧‧First gas detection means

20‧‧‧Second gas detection means

1 is a schematic view of an environmental monitoring system of the present invention.

2 is a view showing an outline of a semiconductor gas sensing element of a first gas detecting means.

Fig. 3 is a graph showing the measurement results of various gases by the semiconductor type gas sensing element of Example 2 (tin oxide-molybdenum oxide) of the present invention.

Fig. 4 is a graph showing the measurement results of various gases by the semiconductor type gas sensing element of Comparative Example 1 (tin oxide).

Fig. 5 is a graph showing the results of measurement of various gases by the semiconductor-type gas sensing element of Example 2 of the present invention in the presence of polyoxygen gas.

Fig. 6 is a graph showing the measurement results of various gases by the semiconductor type gas sensing element of Comparative Example 1 in the presence of polyoxygen gas.

Fig. 7 is a graph showing the measurement results of various gases by the semiconductor type gas sensing element of Example 3 (indium oxide-molybdenum oxide) of the present invention.

Fig. 8 is a graph showing the measurement results of various gases by the semiconductor type gas sensing element of Comparative Example 2 (indium oxide).

Fig. 9 is a graph showing the gas sensitivity when ethanol and acetone were respectively detected by the semiconductor-type gas sensing element of Example 2 of the present invention.

Figure 10 shows the presence of Example 2 in the presence of polyoxyl gas A graph of the rate of change of gas sensitivity when the semiconductor gas sensing element detects ethanol.

Fig. 11 is a table showing the content of cerium oxide, the content of molybdenum oxide, and the rate of change of gas sensitivity.

Fig. 12 is a graph for investigating the relationship between the sensitivity of nine kinds of gases and the gas concentration in the semiconductor type gas sensing element of the present invention.

Fig. 13 is a graph showing the relationship between the sensitivity of nine kinds of gases and the gas concentration in the semiconductor-type gas sensing element of Example 2 of the present invention.

Fig. 14 is a graph showing the results of an environment monitoring system installed in a clean room of a semiconductor manufacturing plant and sensing the gas present in the clean room.

Figure 15 is a schematic diagram of a bridge circuit.

Hereinafter, embodiments of the present invention will be described based on the drawings.

As shown in FIG. 1, the environmental monitoring system Z of the present invention includes a gas sensing unit A that senses a gas component existing in a closed space, and the gas sensing unit A is provided in a closed space. The plurality of gas detecting means 10 and 20 in the different regions are provided with the gas detecting means 10 for detecting the detected value of the predetermined value or more when any of the gas detecting means 10, 20 detects a detection value equal to or greater than a predetermined value. The analysis unit E for analyzing the gas components contained in the ambient gas around the 20th.

Further, the environmental monitoring system Z of the present invention is provided with a monitoring unit F that monitors a change in the amount of components of the gas component.

The enclosed space refers to, for example, a closed space that controls the ingress and egress of internal and external environmental gases. The environmental monitoring system Z of the present invention will be described as a closed space in a clean clean room in which, for example, air whose temperature and humidity are managed are circulated. The clean room is, for example, a device that is installed in a semiconductor manufacturing plant.

In the gas sensing unit A of the present invention, the first gas detecting means 10 and the second gas detecting means 20 are provided, and the detection sensitivity of the alcohol is different between the two. In the gas sensing unit A of the present embodiment, the detection sensitivity of the alcohol in the second gas detecting means 20 is high, and the case where the alcohol is ethanol is described, but the invention is not limited thereto. In the present embodiment, the case where two gas detecting means are provided is described. However, the number of gas detecting means is not limited to this aspect.

The one first gas detecting means 10 includes one first semiconductor type gas sensing element X, and the one second gas detecting means 20 includes one second semiconductor type gas sensing element X'. The first semiconductor-type gas sensing element X and the second semiconductor-type gas sensing element X' are sensing elements of a plurality of gas components that can be sensed by one sensing element, respectively.

Further, the first gas detecting means 10 and the second gas detecting means 20 may be separately provided, but in this case, the gas may be disposed in the vicinity of the same area so as to be sensitive to the gas in the same area.

In the clean room, the following flow-through airflow is managed by the air conditioner. In this case, since the airflow is diffused from the upper layer to the lower layer, for example, the gas sensing unit A may be disposed at the boundary between the upper layer and the lower layer.

As shown in FIG. 2, the first gas detecting means 10 has the first A semiconductor gas sensing element X. The first semiconductor-type gas sensing element X is provided with a noble metal wire 1 and a gas-sensing formed by covering the noble metal wire 1 and using a metal oxide semiconductor containing molybdenum oxide as a main component of tin oxide or indium oxide. a catalyst layer 3 having at least one selected from the group consisting of alumina, vermiculite, lanthanum aluminum oxide, and zeolite as the support on the outer peripheral side of the gas sensing unit 2, and the catalyst layer 3 is provided. At least one of a tungsten oxide or a molybdenum oxide is supported.

The first semiconductor-type gas sensing element X is a hot-wire type semiconductor gas sensing element or a substrate-type semiconductor type gas sensing element, but is not limited thereto. In the present embodiment, a case of forming a hot-wire type semiconductor gas sensing element will be described.

The hot-wire type semiconductor gas sensing element X is provided with a gas sensing unit 2 in a coil-shaped noble metal wire 1 . As the noble metal wire 1, a wire such as platinum, palladium or a platinum-palladium alloy can be used. The wire diameter, the coil diameter, and the number of turns of the noble metal wire 1 are the same as those used in the conventional hot wire type semiconductor gas sensing element, and are not particularly limited.

The gas sensing unit 2 is coated with a metal oxide semiconductor containing tin oxide or indium oxide as a main component, and dried and then sintered. Molybdenum oxide (MoO ₂ , MoO ₃ ) is added to the metal oxide semiconductor system. The content of the molybdenum oxide is, for example, 0.5 to 10 mol%, preferably 1 to 10 mol%. Thereby, the so-called odor component such as ethanol, toluene, acetone, or ethyl acetate can be detected with high sensitivity, and the odor component can be accurately detected even in the presence of a polyoxygen gas.

In a metal oxide semiconductor, in addition to molybdenum oxide, Niobium oxide or lead oxide may also be added. By adding an oxide of cerium or lead to a metal oxide semiconductor, for example, it is highly sensitive to toluene or acetone belonging to an odor component, and is excellent in selectivity with other gases such as hydrogen, methane, and ethylene. A semiconductor gas sensing element X.

When the content of the lanthanum oxide (La ₂ O ₃ ) is, for example, 0.05 to 1 mol%, it has a good gas sensitivity.

Further, the content of lead oxide (PbO) is preferably 0.01 to 1 mol%, for example. Thereby, the sensitivity other than the VOC gas such as hydrogen, methane or ethylene can be lowered, and the odor component can be more easily detected.

A catalyst layer 3 having at least one selected from the group consisting of alumina, vermiculite, lanthanum aluminum oxide, and zeolite as a support is provided on the outer peripheral side of the gas sensing unit 2, and the catalyst layer 3 is supported. At least one of tungsten oxide (WO ₃ ) or molybdenum oxide.

When the content of the tungsten oxide or the molybdenum oxide is 0.1 to 10 mol%, the sensitivity of the alcohol can be sufficiently suppressed.

The alcohol reaching the surface of the catalyst layer 3 is decomposed by the tungsten oxide or the molybdenum oxide contained in the catalyst layer 3. Thereby, even in the case where the alcohol is mixed in the gas to be sensed, the sensitivity of the sensor to the alcohol can be suppressed. Therefore, the first semiconductor-type gas sensing element X of the present configuration is formed so as to be sensitive to the odor component while suppressing the sensitivity to alcohol.

As shown in FIG. 15, the hot-wire type semiconductor gas sensing element X can be incorporated into the bridge circuit together with the fixed resistors R0, R1, and R2. Form a gas sensor. The bridge circuit is constantly or intermittently energized by the power source E to form a temperature suitable for sensing by the hot wire type semiconductor gas sensing element X. Further, when the hot-wire type semiconductor gas sensing element X is adsorbed by the sensing gas, the resistance value changes. Therefore, in the gas sensor of the present embodiment, the change in the resistance value of the hot-wire type semiconductor gas sensing element X can be taken out as the offset voltage, and this can be formed as the sensor output V, whereby the measurement is sensed. The concentration of the gas (odor component).

The second gas-type gas sensing element X' is also provided in the second gas detecting means 20. The second semiconductor-type gas sensing element X' includes the noble metal wire 1 and the gas sensing unit 2.

Since the second semiconductor-type gas sensing element X' used in the second gas detecting means 20 does not contain the catalyst layer 3, the sensitivity to the alcohol component is higher than that of the first gas detecting means 10. At this time, both the first gas detecting means 10 and the second gas detecting means 20 may be disposed in the sensing target space, and the plurality of gas sensing outputs according to the respective sensing means may be used to identify the plural existing in the sensing object space. Gas components (alcohols and other gas components).

That is, in the sensing target space, if the concentration of the alcohol is increased, there is no sensing output of the alcohol component by the first gas detecting means 10, but the sensing output of the alcohol component by the second gas detecting means 20 is changed. high. At this time, if the output of the first gas detecting means 10 is obtained to be larger than the predetermined sensing output, it can be recognized that the gas component other than the alcohol can be sensed, and if the second gas detecting means 20 is obtained The output is greater than the predetermined sensed output and is recognized as being sensible to the alcohol, so Sensitive alcohols and other gas components can be identified simultaneously.

In the environmental monitoring system Z of the present invention, when any of the gas detecting means 10 and 20 detects a detection value equal to or greater than a predetermined value, the gas detecting means 10, 20 for detecting the detected value of the predetermined value or more are provided. The analysis unit E for analyzing the gas components contained in the environmental gas.

The analysis unit E may be any aspect if it can analyze (identify) the plurality of gas components contained in the ambient gas. For example, the analysis unit E may be configured to include a gas chromatography chromatographic separation column, a suction pump for causing a gas such as a carrier gas to flow through a gas chromatographic separation column, and a gas chromatographic separation column to be introduced. The introduction path of the gas and the discharge path of the exhaust gas are provided with a gas component detecting means for detecting the gas component separated by the gas chromatographic separation.

The gas chromatography chromatographic separation column can be carried out by using a separation column for a well-known gas chromatograph. In addition, the gas component detecting means may be a well-known gas detecting means such as the above-described semiconductor type gas sensing element.

The gas components contained in the ambient gas around the gas detecting means 10 and 20 are conveyed to the analysis unit E and analyzed in the analysis unit E. In order to carry out the above-described transportation, the ambient gas such as the collected gas detecting means 10 and 20 may be provided, and the collected ambient gas may be sent to the collecting means (not shown) of the analyzing unit E. .

The trapping means may be any one that can collect the ambient gas and transport it to a desired portion, and may be provided, for example. A pump device and a catheter that suck the ambient gas around the respective gas detecting means 10 and 20 by a syringe or the like, and collect the collected ambient gas to the analysis unit E at a positive pressure or a negative pressure. (pipe) constitutes.

When any of the gas detecting means 10, 20 detects a detection value equal to or greater than a predetermined value, the ambient gas surrounding the gas detecting means 10, 20 detecting the detected value of the predetermined value or more is collected and collected. The ambient gas is sent to the analysis unit E by, for example, a collecting means. When the ambient gas to be transported at this time is introduced into the analysis unit E by the introduction path of the trapping means, the column is separated by gas chromatography, and the ambient gas is developed, and the gas components are sequentially arranged for each gas component. Separation, and is discharged on the side of the discharge path to be discharged. Each of the gas components dissolved in the gas is sequentially supplied to the gas component detecting means, and the type and the like of the gas component can be sensed and analyzed (identified). The concentration of the gas component can be configured to be performed, for example, by the calculation unit B described later.

As described above, when any of the gas detecting means 10, 20 detects a detection value equal to or greater than a predetermined value, the ambient gas around the gas detecting means 10, 20 that detects the detected value of the predetermined value or more is configured. The analysis of the gas components contained therein allows the analysis of the timing of the gas components by the analysis unit E. In other words, when any of the gas detecting means 10 and 20 detects a detection value equal to or greater than a predetermined value, when a desired gas component (any of the alcohol components or other gas components) is sensed, When the analysis unit E analyzes the ambient gas around the gas detecting means 10 and 20 at this timing, the analysis unit E analyzes a desired gas component (any of the alcohol components or other gas components). Therefore, the analysis of the gas composition can be carried out reliably and in detail.

Further, the monitoring unit F monitors a change in the gas component based on, for example, the analysis result of the analysis unit E. The monitoring unit F can use a display means that can instantly monitor, for example, the component amount of the gas component, but is not limited to the above.

By providing the monitoring unit F as shown in the present configuration, it is possible to easily grasp the change in the gas component inside the closed space. The monitoring unit F may be provided inside the closed space or outside the closed space. When the monitoring unit F is provided inside the closed space, even if the monitoring unit F is provided at any position of the near or separated position of the gas sensing unit A, the gas component inside the closed space can be easily grasped. Variety. Further, if the monitoring unit F is provided outside the closed space, even if it is outside the closed space, the change in the gas composition inside the closed space can be easily grasped.

In addition, when any of the gas detecting means 10 and 20 detects a detection value of a predetermined value or more, the monitoring unit F is configured to instruct the collection means to capture the ambient gas around the gas detecting means having a predetermined value or more. The analysis unit E may instruct the analysis of the ambient gas to be transmitted by the collection means.

In the present configuration, the monitoring unit F can recognize the detected values of the gas detecting means 10 and 20, and according to the detected value, the collection of the ambient gas to the collecting means for the desired gas detecting means. The way the instructions are controlled. Further, the monitoring unit F can control the analysis unit E to issue an analysis command of the environmental gas after issuing the capture command. In other words, if the capture command or the analysis command can be executed in the monitoring unit F, the monitoring unit F is provided in the gas sensing unit A, for example. In the case of any position of the near or separated position, or in the case where the monitoring unit F is provided outside the closed space, the capture instruction or the analysis command may be executed at a desired timing.

The monitoring unit F may be configured to have a microcomputer or the like that can execute the capture command or the analysis command.

The environmental monitoring system Z of the present invention can be configured to sense, analyze, and monitor desired gas components based on the sensing output of the first gas detecting means 10 and the sensing output of the second gas detecting means 20.

For example, the difference between the outputs of the first gas detecting means 10 and the second gas detecting means 20 can be calculated to determine the gas component to be sensed. At this time, for example, the normal output (ΔV sensitivity) of both of them is about 0 to 300, and the alarm level is set to 1000 or more. In this case, if the value obtained by subtracting the output of the first gas detecting means 10 from the output of the second gas detecting means 20 is 600 or more, it is determined that the sensed gas component is When the alcohol such as ethanol is 400 or less, it is determined to be other than the alcohol.

The result of the determination as described above is monitored by the monitoring unit F, whereby the change in the component amount of the gas component can be easily monitored.

The gas detecting means 10 and 20 in the gas sensing unit A may be set to a zero point using a clean gas. Thereby, the zero point adjustment of the gas detecting means 10, 20 can be performed reliably.

The environmental monitoring system Z of the present invention is configured to calculate a gas based on an output of a desired gas component sensed by the gas sensing unit A. The calculation unit B of the concentration. The calculation unit B may use a microcomputer or the like that can calculate the gas concentration based on the output signal from the gas sensing unit A.

The calculation unit B is controlled to emit an alarm signal when at least one of the first gas detecting means 10 and the second gas detecting means 20 senses the gas component above the alarm level, and the sense of the gas sensing portion A When the measured output is equal to or greater than the predetermined value, it is sent to the notification unit C that outputs the alarm output, and the notification unit C issues an alarm.

When only the gas component of the alarm level or higher is sensed by the second gas detecting means 20, it may be configured to determine that the alcohol is sensed, and the notification unit C does not issue an alarm. In addition, when at least one of the first gas detecting means 10 and the second gas detecting means 20 continues to sense a gas component equal to or higher than the alarm level for a predetermined time or longer, an alarm is generated.

The notification unit C receives an alarm signal from the calculation unit B, and issues an alarm by sound based on the selected alarm sound signal. The alarm sound can be set, for example, when the gas component to be sensed is an alcohol such as ethanol or when it is other than an alcohol. Thereby, the user can easily recognize the gas component that is sensed, and thus the cause of the prompt alarm can be specified. The notification unit C is composed of a speaker and its drive circuit, and converts an alarm sound signal into an alarm sound for output.

Further, the environmental monitoring system Z of the present invention is provided to correspond to the respective installation positions of the first gas detecting means 10 and the second gas detecting means 20, the respective sensing output values, and the respective detection date and time. Display portion D displayed. With this configuration, the user can easily grasp the status of each detection means.

[Other Embodiments]

In the above-described embodiment, when any of the plurality of gas detecting means 10, 20 detects a detection value equal to or greater than a predetermined value, the ambient gas around the gas detecting means 10, 20 that detects the detected value of the predetermined value or more is described. The gas component contained is analyzed. However, when there are a plurality of gas detecting means that detect a detection value equal to or greater than a predetermined value, it is also possible to analyze the gas component of the ambient gas around the gas detecting means which is the most empty during the previous capture.

Further, when there are a plurality of gas detecting means that detect a detection value equal to or greater than a predetermined value, the gas component of the ambient gas around the gas detecting means having a large number of times (or less) of the predetermined value or more may be analyzed.

Further, when there are a plurality of gas detecting means that detect a detection value equal to or greater than a predetermined value, it is possible to determine whether or not to analyze the ambient gas around any gas detecting means based on the past detection tendency.

When there are a plurality of gas detecting means that detect a detection value equal to or greater than a predetermined value as described above, the gas components of the ambient gas around the gas detecting means are analyzed in the set order. However, in this case, the gas detection is performed in the subsequent order. The ambient gas around the means can also be temporarily captured by the collection means and stored until the order is completed. The storage system may house all or part of the collected ambient gas in a storage unit having an appropriate space.

[Examples] [Example 1]

A method of manufacturing the semiconductor-type gas sensing element used in the environmental monitoring system Z of the present invention will be described below. The semiconductor gas sensing element is produced by using the first gas detecting means 10 (inventive example 1) including the noble metal wire 1, the gas sensing portion 2, and the catalyst layer 3, and the noble metal wire 1 and The second gas detecting means 20 (Inventive Example 2) of the gas sensing unit 2.

A tin oxide (SnO ₂ ) semiconductor paste doped with 0.1 mol% of antimony (Sb+5) to obtain a predetermined electrical conductivity is applied to a platinum coil to form a spherical shape having a diameter of about 0.5 mm. After drying, the mixture was energized to a platinum coil, and the tin oxide was sintered at 650 ° C for 1 hour by Joule heat.

The semiconductor of tin oxide was impregnated with a droplet of 1 mol/L aqueous ammonium molybdate solution and dried at 20 ° C for 60 minutes. After drying, the platinum coil was energized (1 hour), and subjected to heat decomposition treatment at about 600 ° C to carry the molybdenum oxide on the surface of the metal oxide semiconductor (gas sensing portion). The second semiconductor-type gas sensing element X' (Inventive Example 2: used in the second gas detecting means 20) obtained as shown above is incorporated into the bridge circuit, and the sensitivity evaluation of the gas to be sensed is used.

Wherein, when a cerium oxide is added to a metal oxide semiconductor, a semiconductor of tin oxide is impregnated with, for example, a 1 mol/L aqueous solution of cerium nitrate, and when a lead oxide is added to the metal oxide semiconductor, it is impregnated with a semiconductor of tin oxide. For example, a 0.5 mol/L aqueous solution of lead nitrate may be used.

The catalyst layer 3 was produced as follows.

100 g of the alumina powder was added to an aqueous solution (0.1 mol/L) of ammonium tungstate so as to be 0.1 to 10 mol% (the optimum addition amount of 2 mol%) by an impregnation method, followed by drying, and at 700 ° C in an electric furnace. Boil for 2 hours. This was pulverized, and formed into a paste form by water kneading to be applied to the entire surface of the surface of the metal oxide semiconductor. Further, after drying at room temperature, it was heated at 600 ° C for 1 hour and sintered to form.

The first semiconductor-type gas sensing element X (Inventive Example 1: used in the first gas detecting means 10) of the present invention obtained as shown above is incorporated in a bridge circuit, and the sensitivity evaluation for the gas to be sensed is used. .

[Example 2]

The second semiconductor-type gas sensing element X' of the second embodiment of the present invention (adding 2 mol% of molybdenum oxide to the gas sensing portion) and the gas sensing portion containing tin oxide as a main component as Comparative Example 1 In the semiconductor gas sensing element (with no molybdenum oxide added to the gas sensing portion), the sensing sensitivity of each gas (DC2.4V energization (10 ohm load)) was examined. The gases used were ethanol, methane, isobutane, hydrogen, carbon monoxide, toluene, acetone, ethyl acetate.

The measurement results obtained by the second semiconductor-type gas sensing element X' of the second embodiment of the present invention are shown in Fig. 3, and the measurement results obtained by the semiconductor-type gas sensing element of the comparative example 1 are shown in Fig. 4.

Figure 3 is a second semiconductor type gas sensation in Example 2 of the present invention. In the measuring element X', it was found that the gas sensitivity to ethanol, toluene, acetone, and ethyl acetate which are odor components is more sensitized than methane and carbon monoxide. On the other hand, in Fig. 4, in the semiconductor-type gas sensing element of Comparative Example 1, the gas sensitivity of any gas is not clearly sensitized, and in the odor component and the flammable gas, a clear difference in gas sensitivity is not found. .

Therefore, in the second semiconductor-type gas sensing element X', it is considered that the odor component can be detected with high sensitivity by adding molybdenum oxide to the gas sensing portion.

[Example 3]

In the second semiconductor-type gas sensing element X' of the second embodiment of the present invention and the semiconductor-type gas sensing element of the comparative example 1, the gas sensitivity in the presence of polyoxymethane gas (OMCTS: Octamethylcyclotetrasiloxane, 10 ppm) was investigated. Variety. The gas system of the sensing object is formed into air or ethanol (5 to 100 ppm).

The measurement results obtained by the second semiconductor-type gas sensing element X' of the second embodiment of the present invention are shown in Fig. 5, and the measurement results obtained by the semiconductor-type gas sensing element of the comparative example 1 are shown in Fig. 6.

According to Fig. 5, in the second semiconductor-type gas sensing element X' of the second embodiment of the present invention, it is considered that a stable (substantially constant) gas sensitivity can be obtained even in the presence of polyoxygen gas. On the other hand, in Fig. 6, in the semiconductor-type gas sensing element of Comparative Example 1, especially in the initial stage of exposure of the polyfluorene gas, since the gas sensitivity is rapidly changed, it is considered to be displayed in the presence of polyoxygen gas. Stable gas sensitivity.

[Example 4]

In the method for fabricating the second semiconductor-type gas sensing element X' of the second embodiment of the present invention described in the first embodiment, the semiconductor paste of tin oxide used is substituted for the semiconductor paste of indium oxide (In ₂ O ₃ ). A paste is used to make a semiconductor gas sensing element. The second semiconductor-type gas sensing element X' obtained as described above (Inventive Example 3: 2 mol% of molybdenum oxide added to the gas sensing portion) is incorporated into a bridge circuit for use in the pair of sensed gases Sensitivity assessment.

[Example 5]

The second semiconductor-type gas sensing element X' of the third embodiment of the present invention and the semiconductor-type gas sensing element having the gas sensing portion containing indium oxide as a main component as Comparative Example 2 (no molybdenum oxidation added to the gas sensing portion) In the case, the sensitivity of various gases (DC2.4V when energized (10 ohm load)) was investigated. The gases used were ethanol, hydrogen, toluene, acetone, and ethyl acetate.

The measurement results obtained by the second semiconductor-type gas sensing element X' of Example 3 of the present invention are shown in Fig. 7, and the measurement results obtained by the semiconductor-type gas sensing element of Comparative Example 2 are shown in Fig. 8.

Fig. 7 shows that the second semiconductor-type gas sensing element X' of the third embodiment of the present invention is considered to be sensitized to the gas sensitivity of ethanol, toluene, acetone, and ethyl acetate which are odor components. On the other hand, from Fig. 8, in the semiconductor type gas sensing element of Comparative Example 2, any gas The gas sensitivity is also almost sensitized, and no clear difference in gas sensitivity is found between the odor component and the flammable gas.

[Example 8]

In the second semiconductor-type gas sensing element X' of the second example of the present invention, the effective concentration of the molybdenum oxide added to the gas sensing portion was investigated.

The semiconductor type gas sensing element of the eleven types (Table 1) was produced so that the content of the molybdenum oxide supported on the surface of the gas sensing portion was 0.001 to 30 mol%. For these semiconductor-type gas sensing elements, gas sensitivity when 100 ppm of ethanol belonging to an odor component and 100 ppm of acetone were separately detected was examined. The results are shown in Table 1 and Figure 9.

As a result, it is considered that the content of molybdenum oxide is 0.1 mol. Above 100%, especially above 0.5 mol%, has excellent gas sensitivity.

Further, in the above-described eleven types of semiconductor-type gas sensing elements, changes in gas sensitivity in the presence of polyoxygen gas (OMCTS) were investigated. The change in the gas sensitivity is expressed by a sensitivity change rate (measured value at 20 hours of exposure/initial measured value) of ethanol of 100 ppm when the semiconductor gas sensing element is exposed to 10 ppm of the polyoxygen gas. The results are shown in Table 2 and Figure 10.

Before the semiconductor gas sensing element is exposed to the polyoxygen gas, the rate of change of the gas sensitivity is about 1.0 to 1.5, which is considered to have a good gas sensitivity. If the content of molybdenum oxide is 0.5 to 10 mol%, it is considered that the rate of change of gas sensitivity is in the range of 1.0 to 1.5. In addition, if the content of molybdenum oxide is 1 to 10 mol%, due to gas sensitivity The rate of change is in the range of 1.0 to 1.2, and is therefore considered to be a better gas sensitivity.

Therefore, it is clear that if the content of the indium oxide is 0.5 to 10 mol%, the odor component can be accurately detected in the presence of a polyoxygen gas.

[Example 9]

In the second semiconductor-type gas sensing element X' of the second example of the present invention, the effective concentration of the cerium oxide added to the gas sensing portion was examined.

Adding cerium oxide 0 to 3 mol% to the metal oxide semiconductor to which the molybdenum oxide was added, and investigating the rate of change of the gas sensitivity (polyoxygen gas) before and after the exposure (10 ppm, exposure for 100 hours) before the polyoxygen gas The 100 ppm sensitivity after exposure/100 ppm sensitivity before exposure to polyoxyl gas) is in the range of 1.0 to 1.5. As described above, when the semiconductor gas sensing element is exposed to the polyoxygen gas, the rate of change of the gas sensitivity is about 1.0 to 1.5, which is considered to be unaffected by the polyoxygen gas.

The results are shown in Fig. 11 (a). From Fig. 11(a), the change rate shows that 1.0 to 1.5 is a range in which the content of the cerium oxide is 0.05 to 1 mol%. Therefore, if the content of the cerium oxide is in the range of 0.05 to 1 mol%, it is considered to be unaffected by the polyoxygen gas.

Further, in the range of 0 to 3 mol% of the cerium oxide, the sensitivity (mV) to 100 ppm of ethanol was measured. When the molybdenum oxide is added to the metal oxide semiconductor, 2 mol%, and the tungsten oxide is added to the catalyst layer 3, the presence or absence of the catalyst layer 3 and the content of the lead oxide are The semiconductor gas sensing element changed between 0.01 and 1 mol% was measured. The result is shown in Fig. 11(b).

The highest sensitivity of ethanol in the second semiconductor-type gas sensing element X' (Inventive Example 2) having no catalyst layer 3 was 251 mV when the cerium oxide was 0.1 mol%. In the present embodiment, the sensitivity is determined to be 70% (175 mV) or more of the measured value, and the sensitivity of the first semiconductor-type gas sensing element X (Example 1 of the present invention) having the catalyst layer 3 is obtained. When it is 1/2 or less of the second semiconductor-type gas sensing element X' (Inventive Example 2) having no catalyst layer 3, it is judged that the ethanol removal performance is excellent. As a result, it was found that if the content of the cerium oxide is in the range of 0.05 to 1 mol%, the conditions are satisfied, and the removal performance of ethanol is excellent.

[Example 10]

In the second semiconductor-type gas sensing element X' of the second example of the present invention, the effective concentration of the lead oxide added to the gas sensing portion was examined.

When the content of the molybdenum oxide supported on the surface of the gas sensing portion is 0.5, 2.0, or 10 mol%, the content of the lead oxide is in the range of 0.005 to 5 mol%, respectively. The second semiconductor-type gas sensing element X' of the type (Table 3) (a total of 21 types). For each of the second semiconductor-type gas sensing elements X', the gas sensitivity when 100 ppm of ethanol and 100 ppm of hydrogen were detected was examined. The effective concentration of the lead oxide is preferably in a range in which the selectivity of the odor component is excellent. The range in which the selectivity of the odor component is excellent is such that the ratio of the flammable gas sensitivity to the ethanol sensitivity is 1 or less. The results are shown in Table 3.

As a result, when the content of the lead oxide is in the range of 0.01 to 5 mol%, it is found that the ratio of the hydrogen sensitivity/ethanol sensitivity is 1 or less. However, even in the case where the ratio of the hydrogen sensitivity/ethanol sensitivity is 1 or less, the sensitivity of the odor component (ethanol) is preferably low. Therefore, the upper limit of the content of lead oxide is the highest sensitivity (the content of molybdenum oxide is 0.5 mol%, the content of lead oxide). Among the contents of the lead oxide having a sensitivity of 50% or more of a sensitivity of 170 mV in the case of 0.5 mol%, it is preferably formed to be the maximum. Based on these circumstances, the content of the lead oxide is preferably in the range of 0.01 to 1 mol%.

Therefore, when the content of the lead oxide is in the range of 0.01 to 1 mol%, it is clear that the sensitivity of hydrogen can be lowered, and the odor component can be more easily detected. However, although the result is not shown, not only hydrogen but also the sensitivity other than VOC gas such as methane or ethylene can be similarly lowered.

[Example 11]

When the amount of tungsten oxide added to the catalyst layer 3 was changed between 0 and 10 mol%, it was investigated how the sensitivity to 100 ppm of ethanol and the sensitivity to 100 ppm of acetone changed. In the metal oxide semiconductor system, 2 mol% of molybdenum oxide, 0.5 mol% of cerium oxide, and 0.5 mol% of lead oxide are added. The results are shown in Table 4.

As a result, even in the case where the amount of addition of tungsten oxide was changed, the sensitivity to 100 ppm of acetone was not found to be significantly changed. In this case, when the amount of the tungsten oxide added is 0.1 to 10 mol%, the sensitivity of 100 ppm of ethanol is found to be significantly suppressed as compared with the case where the amount of tungsten oxide added is 0.

In the present embodiment, the case where tungsten oxide is used as the carrier supported on the catalyst layer 3 will be described. However, even if it is molybdenum oxide, the same result is displayed (the result is not shown). .

[Example 12]

In the first semiconductor-type gas sensing element X of the first example of the present invention (Inventive Example 1, metal oxide semiconductor: containing molybdenum oxide 2 mol%, cerium oxide 1 mol%, lead oxide 0.5 mol%) , catalyst layer: containing tungsten oxide 2 mole %), investigated for 9 gases (ethanol, styrene, xylene, toluene, trimethylamine, ammonia, isobutanol, methyl acetate, acetone) The relationship between sensitivity and gas concentration (Figure 12). As can be seen from Fig. 12, the sensitivity is sufficiently obtained from 1 ppm for all the gases, and the sensitivity of ethanol is the lowest, and the separation of ethanol from other gases is also excellent.

As described above, the first semiconductor-type gas sensing element X of the present configuration can detect the odor component (hydrogen sulfide) with high sensitivity while suppressing the sensitivity to alcohol.

Further, in the second semiconductor-type gas sensing element X' (metal oxide semiconductor: containing molybdenum oxide 2 mol%, niobium oxide 1 mol%, lead oxide 0.5 mol%) of the second example of the present invention For the relationship between the sensitivity of nine gases (ethanol, styrene, xylene, toluene, trimethylamine, ammonia, isobutanol, methyl acetate, acetone) and gas concentration Survey (Figure 13). As a result, ethanol was found to be completely unseparated from other gases.

In the present embodiment, the case where alumina is used as the support of the catalyst layer 3 will be described, but even in the case of any of vermiculite, lanthanum aluminum oxide, and zeolite, or the plural Body, also shows the same result. Further, although the case where tungsten oxide is used as the carrier carried on the catalyst layer 3 has been described, the same result is exhibited even if it is a molybdenum oxide (all results are not shown).

[Example 13]

The production includes: a first semiconductor-type gas sensing element X (Inventive Example 1: used in the first gas detecting means 10), and a second semiconductor-type gas sensing element X' (Inventive Example 2: used in the second The gas sensing unit A of the gas detecting means 20) installs the environmental monitoring system Z having the gas sensing unit A in a clean room of a semiconductor manufacturing plant, and senses the gas existing in the clean room (FIG. 14).

In the first gas detecting means 10, in terms of the odor component, the VOC gas is sensed at a constant low level (ΔV sensitivity of about 200 to 600 degrees). In the clean room, use ethanol and rub it between AM10:00~12:00. At this time, in this time interval, the second gas detecting means 20 senses the ethanol component with an output having a ΔV sensitivity of about 1500.

That is, the environmental monitoring system Z is disposed in the clean room, whereby both of the sensing ethanol and the VOC gas can be simultaneously recognized.

In any of the first gas detecting means 10 and the second gas detecting means 20, the alarm level is also formed when the ΔV sensitivity is 1000 or more.

Therefore, in order to analyze the gas component contained in the ambient gas around the second gas detecting means 20 in which the detected value of the alarm level or more is detected, the ambient gas around the second gas detecting means 20 is trapped by the collecting means. The collected ambient gas is sent to the analysis unit E for analysis. In the analysis unit E, a fluororesin column tube having an inner diameter of 4 mm and a total length of 20 cm as a gas chromatographic separation column is used, and a polyphenylene ether (PPE) filler material having a particle diameter of 80 to 100 μm is filled in a ring. - HP (manufactured by GL Sciences Co., Ltd.) analyzed gas components at a column temperature of 25 ° C and a carrier gas flow rate of 60 ml/min.

The analysis result of the gas component obtained by the analysis of the analysis unit E is immediately monitored by the monitoring unit F. The analysis result is monitored in the monitoring unit F as described above, whereby the change in the gas composition inside the closed space can be easily grasped.

[Industrial Applicability]

In the present invention, an environmental monitoring system including a gas sensing unit that senses a gas component existing inside the closed space can be utilized.

A‧‧‧Gas Sensing Department

B‧‧‧ Computing Department

C‧‧‧Notification Department

D‧‧‧Display Department

E‧‧‧Analysis Department

F‧‧‧Monitor Department

Z‧‧‧Environmental Monitoring System

10‧‧‧First gas detection means

20‧‧‧Second gas detection means

Claims (7)

An environmental monitoring system including a gas sensing unit that senses a gas component existing inside a closed space, wherein the environmental monitoring system is characterized in that the gas sensing unit is provided in the closed space. The complex gas detecting means in the different regions includes: when any of the gas detecting means detects a detection value equal to or greater than a predetermined value, the ambient gas surrounding the gas detecting means that detects the detected value of the predetermined value or more The analysis unit of the gas component is analyzed. The environmental monitoring system according to claim 1, wherein the gas sensing unit includes: a first gas detecting means and a second gas detecting means, wherein the sensing characteristics of the sensed gas are different between the two Sensing, analyzing, and monitoring the desired gas component based on the sensing output of the first gas detecting means and the sensing output of the second gas detecting means. An environmental monitoring system according to claim 1 or 2, wherein the gas detecting means in the gas sensing unit sets a zero point using a clean gas. An environmental monitoring system according to claim 1 or 2, further comprising: a monitoring unit that monitors a change in the gas component; and an ambient gas that collects the gas detecting means, and collects the environment The gas is sent to the collection means of the analysis unit, When any of the gas detecting means detects a detection value equal to or greater than a predetermined value, the monitoring unit instructs the collection means to capture an ambient gas around the gas detecting means having a predetermined value or more, and instructs the analysis unit to analyze the The ambient gas to be transported by the means of capture. The environmental monitoring system of claim 2, wherein the first gas detecting means comprises: a noble metal wire; covering the noble metal wire, using a metal oxide containing molybdenum oxide as a main component of tin oxide or indium oxide a gas sensing portion formed of a semiconductor; and a catalyst layer containing at least one selected from the group consisting of alumina, vermiculite, lanthanum aluminum oxide, and zeolite as a support on the outer peripheral side of the gas sensing portion The catalyst layer carries at least one of a tungsten oxide or a molybdenum oxide as the first semiconductor-type gas sensing element. The environmental monitoring system according to claim 5, wherein the second gas detecting means includes a second semiconductor type gas sensing element that does not include a catalyst layer in the first gas detecting means. An environmental monitoring system according to claim 5 or 6, wherein at least one of a cerium oxide and a lead oxide is added to the metal oxide semiconductor.