Gas treatment apparatus and method for detecting removable target substance

Abstract

To determine, even when a gas contains a plurality of different types of removable target substances, whether or not the concentration of the removable target substances contained in the gas after passing through the filter is equal to or less than a threshold, without detecting the concentration of each removable target substance.SOLUTION: A gas treatment apparatus 10 for removing a plurality of different types of removable target substances contained in a gas by passing the gas therethrough, comprises: a first filter 12 that removes the removable target substances from the gas as it passes therethrough; a first sensor 13 for detecting the concentration of substances contained in the gas after passing through the first filter 12; and a determination part 14 for determining whether or not the concentration of the substances detected by the first sensor 13 exceeds a preset threshold. The threshold is set to be one-tenth or less of the management concentration of a first removable target substance. The first removable target substance is a removable target substance that initially breaks through the first filter 12 when making the gas pass through the first filter 12 so as to remove the removable target substances from the gas containing the plurality of different types of removable target substances.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a gas treatment apparatus that removes a plurality of different objects to be removed by passing a gas containing the objects to be removed, and a method for detecting the objects to be removed.

Background Art

[0002] Conventionally, an organic solvent treatment apparatus for removing objects to be removed such as volatile organic solvents contained in the air in a factory work environment is known. For example, Patent Document 1 shows a treatment apparatus that passes a gas containing a volatile organic solvent through an adsorption tower (filter) filled with an adsorbent to adsorb and remove the organic solvent. The gas from which the object to be removed has been removed by the treatment apparatus is discharged into the work environment of the factory.

[0003] When the filter used in the treatment apparatus adsorbs an amount of the object to be removed exceeding a certain level, it can no longer adsorb more of the object to be removed, and the object to be removed passes through the filter. For this reason, the concentration of the object to be removed is detected by a detection tube on the downstream side of the filter to confirm whether the gas passing through the filter contains the object to be removed. Examples of the detection tube include those that manually collect gas and detect the concentration of the object to be removed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with a detection tube, an operator has to manually collect gas and visually check the concentration. In addition, since a detection tube can only detect one type of object to be removed, when a plurality of objects to be removed are mixed in the gas, the concentration of each object to be removed has to be detected by a detection tube for each object to be removed, which imposes a heavy workload on the operator.

[0006] The present invention has been made in view of the above problems, and even when a gas contains a plurality of removal targets of different types, it is possible to confirm whether or not the gas that has passed through the filter contains a removal target with a small work load. An object of the present invention is to provide a gas treatment apparatus and a method for detecting a removal target.

Means for Solving the Problems

[0007] To achieve the above object, the present invention includes the subject matter described in the following items.

[0008] Item 1: A gas treatment apparatus that passes a gas and removes a plurality of removal targets of different types among the substances contained in the gas, A first filter that removes a removal target by passing the gas, A first sensor for detecting the concentration of the substance contained in the gas that has passed through the first filter, A determination unit that determines whether or not the concentration of the substance detected by the first sensor exceeds a set threshold value, The threshold value is set to be equal to or less than one-tenth of the control concentration of the first removal target, The first removal target is a removal target that first breaks through the first filter when the first filter is passed to remove the removal target from the gas. Gas treatment apparatus.

[0009] Item 2: The gas treatment apparatus according to Item 1, further comprising an alarm unit that issues an alarm when the determination unit determines that the concentration of the substance contained in the gas exceeds a threshold value.

[0010] Item 3: The gas treatment apparatus according to Item 1 or 2, further comprising a second filter through which the gas that has passed through the first filter passes.

[0011] Item 4: The gas treatment apparatus according to Item 3, further comprising a second sensor for detecting the concentration of the substance contained in the gas that has passed through the second filter.

[0012] Item 5: A method for detecting a target substance to be removed by a gas treatment device that passes gas and removes a plurality of target substances of different types among the substances contained in the gas, comprising: identifying a first target substance to be removed that first breaks through the first filter when the gas is passed through the first filter to remove the target substance from the gas, and determining a threshold value according to the first target substance to be removed; removing the target substance from the gas by passing the gas through the first filter; determining whether the concentration of the substance contained in the gas that has passed through the first filter exceeds the threshold value. A method for detecting a target substance to be removed.

Advantages of the Invention

[0013] According to the gas treatment device and the method for detecting a target substance to be removed of the present invention, when removing a plurality of target substances of different types among the substances contained in the gas, by identifying the first target substance to be removed that first breaks through the first filter and setting the threshold value, it can be confirmed by the first sensor that all the target substances contained in the gas are below the threshold value. Therefore, compared with the case of detecting the concentration of all the target substances contained in the gas using a detector tube as in the prior art, it is possible to detect whether the gas passing through the filter contains a target substance with less effort and workload.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0015] Embodiments of the present invention will be described with reference to the drawings. The gas treatment apparatus 10 of the present invention is, for example, attached to an exhaust apparatus 100 and used as shown in FIG. 1. The exhaust apparatus 100 is used, for example, at a work site where chemical substances are manufactured and handled, and is for suppressing the diffusion of volatile harmful substances generated during work. The exhaust apparatus 100 includes a pair of hoods 101 and 102 arranged on the left and right, and a one-way air flow is generated from one hood 101 toward the other hood 102. By setting the work place between the pair of hoods 101 and 102, the generated harmful substances are sucked into the other hood 102 together with the air. Thereby, the scattering of harmful substances around is suppressed. Note that the exhaust apparatus 100 is not limited to the configuration of FIG. 1, and any configuration may be used as long as it can suck in harmful substances.

[0016] The gas treatment apparatus 10 passes gas and removes a plurality of objects to be removed of different types among the substances contained in the gas. The gas treatment apparatus 10 is connected to the other hood 102 by a pipe 103, removes the objects to be removed, which are harmful substances, from the gas sucked by the other hood 102, and returns it to the atmosphere at the work site. In the present embodiment, the other hood 102 of the exhaust apparatus 100 sucks in a gas containing a plurality of objects to be removed of different types, and the gas treatment apparatus 10 removes the plurality of objects to be removed from such a gas.

[0017] Typical examples of the objects to be removed include acetone, ethyl acetate, isopropyl alcohol, methyl ethyl ketone, isobutyl alcohol, toluene, methyl isobutyl ketone, n-butanol, normal butyl acetate, xylene, isobutyl acetate, butyl cellosolve, and the like. Further, the objects to be removed are not limited to the above, and any substance that can be removed by the first filter 12 of the gas treatment device 10 described later may be used. Among the organic solvents listed as the substances to be treated under the Permissible Regulations for the Prevention of Organic Solvent Poisoning (Ministry of Labor Ordinance No. 36 of 1972) determined by the Ministry of Health, Labor and Welfare of Japan (Special Permission for Implementation of Measures for Prevention of Emission Suppression), those that can be removed by the first filter 12 of the gas treatment device 10 may also be used.

[0018] The internal structure of the gas treatment device 10 is shown in FIG. 2. The gas treatment device 10 includes a first filter 12 that removes a plurality of different types of objects to be removed from the substances contained in the gas as the gas passes through, inside a housing 11, a first sensor 13 for detecting the concentration of the substances contained in the gas that has passed through the first filter 12, and a determination unit 14 that determines whether or not the concentration of the substances detected by the first sensor 13 exceeds a threshold value. Further, in the present embodiment, a second filter 15 provided on the downstream side of the first filter 12 and the first sensor 13, through which the gas that has passed through the first filter 12 passes, and a second sensor 16 for detecting the concentration of the substances contained in the gas that has passed through the second filter 15 are provided.

[0019] The threshold value is set to be 1 / 10 or less of the control concentration of the first object to be removed. The setting of the threshold value will be described later. Here, the first object to be removed is the object to be removed that first breaks through the first filter 12 when the first filter 12 is passed through in order to adsorb and remove the object to be removed from the gas containing a plurality of different types of objects to be removed. Breakthrough means a state in which the object to be removed exceeds the limit of removal by the filter and passes through the filter when the object to be removed is removed by the filter.

[0020] As shown in FIG. 2, the pipe 103 of the exhaust device 100 communicates with the gas introduction space 17 provided below the gas treatment device 10, and gas is introduced from the other hood 102 of the exhaust device 100 into the gas introduction space 17. In the direction of gas flow, the side closer to the exhaust device 100 is referred to as the upstream side, and the side farther from the exhaust device 100 is referred to as the downstream side. In the embodiment of FIG. 2, the gas flows from below to above, with the upstream side being the lower side and the downstream side being the upper side. Note that the direction of gas flow within the gas treatment device 10 is not limited to this, and for example, it may be a horizontal direction, an oblique direction with respect to the horizontal direction, or may flow from the upper side to the lower side in the vertical direction.

[0021] At the upper part of the gas introduction space 17, a first support plate 18 for supporting the first filter 12 is provided. The first support plate 18 is provided with through holes (not shown) so that gas can pass through freely. The first filter 12 is placed on the upper surface of the first support plate 18. The first filter 12 is provided so as to block all the through holes of the first support plate 18, preventing the gas passing through the through holes from flowing above the first filter 12 without passing through the first filter 12. In the present embodiment, the side surface of the first support plate 18 is in contact with the inner surface of the housing 11 of the gas treatment device 10, and all the gas flowing upward from the gas introduction space 17 passes through the through holes and passes through the first filter 12.

[0022] The first filter 12 may be composed of a plurality of rectangular parallelepiped members 12a to 12e arranged without gaps. The material constituting the first filter 12 is a material containing activated carbon in the present embodiment, but is not limited to this, and may be a material containing zeolite, silica gel, clay mineral, metal oxide, porous glass, etc., or may be a material in which various adsorbents are mixed according to the adsorption characteristics. With these materials, the objects to be removed contained in the gas are adsorbed by the first filter 12.

[0023] As shown in FIG. 3, on the upper surface of the first filter 12, a first suction pipe 19 for sucking the gas that has passed through the first filter 12 is arranged. In the present embodiment, the first suction pipe 19 includes a plurality (three) of branch pipes 19a to 19c arranged in parallel with a predetermined interval therebetween, and a connecting pipe 19d that connects one end of the three branch pipes 19a to 19c. The branch pipes 19a to 19c and the connecting pipe 19d communicate with each other inside. The connecting pipe 19d is connected to a first pump 20 (FIG. 2) via a first sensor 13. A plurality of through holes 19e are formed in each of the branch pipes 19a to 19c of the first suction pipe 19. By operating the first pump 20, the gas that has passed through the first filter 12 is sucked into the first suction pipe 19 through the through holes 19e. The first pump 20 only needs to be able to suck gas, and a known suction pump is used. Since the first suction pipe 19 includes a plurality of branch pipes 19a to 19c, and each of the branch pipes 19a to 19c is arranged on the upper surface of the first filter 12 with a predetermined interval therebetween, the gas can be sucked from a wide range of the first filter 12 in a plan view. Note that the first suction pipe 19 may be in any form as long as it can suck the gas that has passed through the first filter 12, and the number of the branch pipes 19a to 19c and the size of the through holes 19e are not limited. Also, the first suction pipe 19 may be placed in contact with the upper surface of the first filter 12, or may be arranged above the upper surface of the first filter 12 at an interval by a support member (not shown) and below a second support plate 22 described later.

[0024] The first sensor 13 detects the concentration of substances contained in the gas that has passed through the first filter 12 and is sucked by the first suction pipe 19. When the first filter 12 has broken through and the first object to be removed has passed through, but the first filter 12 has removed objects to be removed other than the first object to be removed, the first sensor 13 measures the concentration of the first object to be removed. Also, when the gas contains substances that are not objects to be removed, the first sensor 13 detects the concentrations of these substances and the first object to be removed. Any sensor can be used for the first sensor 13. For example, a hot-wire semiconductor type sensor may be used. A hot-wire semiconductor type sensor is an integrated unit of a metal oxide semiconductor (sensitive material) and a heater, and detects the change in electrical conductivity due to gas adsorption on the surface of the metal oxide semiconductor to detect the concentration of a specific substance in the gas.

[0025] Above the first suction pipe 19, a second support plate 22 is provided, and a second filter 15 is supported on the second support plate 22. On the upper surface of the second filter 15, a second suction pipe 23 is provided. The second suction pipe 23 is connected to a second pump 24 via a second sensor 16. The second filter 15 is provided to surely remove the object to be removed in case the object to be removed passes through the first filter 12.

[0026] Since the configurations of the second support plate 22, the second filter 15, the second suction pipe 23, the second sensor 16, and the second pump 24 are the same as the configurations of the first support plate 18, the first filter 12, the first suction pipe 19, the first sensor 13, and the first pump 20 respectively, the description thereof is omitted.

[0027] The first sensor 13 and the second sensor 16 are connected to a control device 21 including a determination unit 14. The control device 21 is a general-purpose computer including a CPU, a memory, and a recording device (e.g., a hard disk). The CPU reads various programs stored in the hard disk into the memory and executes various arithmetic processes using the memory as a work area. The determination unit 14 is realized as a function of the CPU.

[0028] When the determination unit 14 receives the detection value indicating the concentration of the substance contained in the gas that has passed through the first filter 12 and the second filter 15 from the first sensor 13 and the second sensor 16, it determines whether or not the detection value exceeds the threshold value.

[0029] A third support plate 25 is provided above the second suction pipe 23, and the third support plate 25 supports the blower 26. The blower 26 further flows the gas that has passed through the second filter 15 upward. Note that the blower may be supported by the inner surface of the housing 11. The blower 26 only needs to be able to send the gas upward, and any blower can be used.

[0030] One or more ventilation holes 11b are provided in the upper surface 11a of the housing 11, and the gas that has passed through the second filter 15 passes through the ventilation holes 11b and is discharged outside the housing 11 and returned to the atmosphere at the work site.

[0031] On the front surface of the housing 11, for example, a touch panel 27 (FIG. 1) is provided. The touch panel 27 is connected to the control device 21 and functions as an alarm unit. When the determination unit 14 of the control device 21 determines that the concentration of the substance contained in the gas exceeds the threshold value, an alarm is issued on the touch panel 27 assuming that the first filter 12 has broken through. Note that the alarm unit is not limited to the touch panel 27, and any means may be used as long as it can issue an alarm to the operator, such as a sound generation device such as a speaker or a light generation device such as a lamp. Further, the touch panel 27 may function as an input unit to the control device 21, and an operator inputs parameters such as the threshold value used in the control device 21, and instructions for starting and stopping the operation of the gas treatment device 10 and the exhaust device 100 via the touch panel 27.

[0032] (Detection method of object to be removed) A method for detecting a target substance to be removed by the above gas treatment apparatus will be described. The detection method includes a step (S1) of identifying a first target substance to be removed that first breaks through the first filter when the gas containing a plurality of target substances of different types is passed through the first filter 12 to remove the target substances, and determining a threshold value according to the first target substance; a gas treatment step (S2) of removing the target substances by passing the gas containing a plurality of target substances of different types through the first filter 12; and a step (S3) of determining whether the concentration of the substance contained in the gas that has passed through the first filter 12 exceeds the threshold value.

[0033] (Method for Identifying the First Target Substance and Setting the Threshold Value) As described above, in the determination unit 14, when receiving the detection values indicating the concentration of the substance contained in the gas from the first sensor 13 and the second sensor 16, it determines whether the detection values exceed the threshold value. Usually, it is unknown what target substances are contained in the gas to be processed by the gas treatment apparatus 10. Therefore, a step of identifying at least the first target substance and setting the threshold value used in the determination unit 14 is performed (S1).

[0034] First, a step of obtaining the relational expression between the concentration of the first target substance in the gas and the detection value of the first sensor 13 is performed. A filter containing activated carbon is attached to the downstream side of the first filter 12, and a predetermined amount of gas is passed through the first filter 12 and the filter. The detection value (voltage value) of the first sensor 13 immediately before the predetermined amount of gas finishes passing is measured. The target substances that have passed through the first filter 12 are adsorbed on the filter. The filter is replaced, a different amount of gas from the previous time is passed through, and the detection value (voltage value) of the first sensor 13 immediately before the gas finishes passing is measured. This is repeated a plurality of times.

[0035] The filter has the objects to be removed that have passed through the first filter 12 adsorbed thereon. The filter is chemically analyzed to obtain the adsorption amount for each object to be removed. The object to be removed that is most adsorbed on the filter is regarded as the first object to be removed that first breaks through the first filter 12, and the concentration of the first object to be removed contained in the gas that has passed through the first filter 12 is obtained from the adsorption amount of the first object to be removed adsorbed on the filter. The same chemical analysis is performed for each filter. Thereby, a relational expression (graph) between the concentration of the first object to be removed and the detection value of the first sensor 13 as shown in, for example, FIG. 6(A) can be obtained.

[0036] Note that the above concentration measurement is an example, and any method may be used as long as the concentration can be measured, not limited to the filter.

[0037] Also, by the above chemical analysis, the objects to be removed adsorbed on the filter can be identified. Note that the creation of the relational expression (graph) and the identification of the objects to be removed may be performed in parallel by chemical analysis.

[0038] The relational expression between the concentration of the first object to be removed and the detection value of the first sensor 13 also varies depending on the type of the substance that is the first object to be removed, the types of the objects to be removed other than the first object to be removed contained in the gas, the types of the substances that are not objects to be removed, and the mixing ratio of the first object to be removed in the gas with the objects to be removed other than the first object to be removed and the substances that are not objects to be removed. Therefore, every time the gas to be processed by the gas treatment device 10 is changed, the above steps are performed to obtain the relational expression and determine the threshold value.

[0039] Next, a step of determining the threshold value used by the determination unit 14 is performed. First, the control concentration of the specified first object to be removed is obtained. The control concentration is predetermined as will be described later. Then, from the relational expression between the concentration of the first object to be removed in the gas and the detection value of the first sensor 13, the detection value of the first sensor 13 corresponding to a concentration that is 1 / 100 or more and 1 / 10 or less of the control concentration of the first object to be removed is set as the threshold value. FIG. 6(B) is an enlarged view of the dotted line portion of FIG. 6(A). In this example, since the control concentration of the first object to be removed is 200 ppm, the concentration corresponding to the threshold value is set to 20 ppm, which is 1 / 10 of the control concentration, and 2.4 V, which is the detection value of the first sensor 13 corresponding to 20 ppm, is set as the threshold value. The threshold value is arbitrarily determined according to the type of the first object to be removed, but in order to avoid the object to be removed from diffusing into the atmosphere, it is preferably set to the smallest possible value.

[0040] The control concentration is an index for determining the control category when judging the quality of work environment management from the results of work environment measurements carried out in accordance with work environment measurement standards in order to evaluate the state of the work environment regarding harmful substances in the process of promoting work environment management. The control concentration is specified in the separate table of Article 65-2, Paragraph 2 of the Industrial Safety and Health Act (Law No. 57 of 1972).

[0041] Typical objects to be removed and their control concentrations in this embodiment are as follows. The values in parentheses are the control concentrations.

[0042] Acetone (500 ppm), Ethyl acetate (200 ppm), Isopropyl alcohol (200 ppm), Methyl ethyl ketone (200 ppm), Isobutyl alcohol (50 ppm), Toluene (20 ppm), Methyl isobutyl ketone (20 ppm), n-Butanol (25 ppm), Normal butyl acetate (150 ppm), Xylene (50 ppm), Isobutyl acetate (150 ppm), Butyl cellosolve (25 ppm)

[0043] In addition, when the second filter 15 is the same as the first filter 12 and the second sensor 16 is the same as the first sensor 13 as in this embodiment, the threshold value obtained by the first filter 12 and the first sensor 13 may be used as the threshold value for the detection value of the second sensor 16.

[0044] (Gas treatment in the gas treatment apparatus 10) Before the gas treatment apparatus 10 performs gas treatment, first, a threshold value is set and input to the control device 21 from the touch panel 27.

[0045] The gas treatment (S2) by the gas treatment apparatus 10 is performed. In the gas treatment, a gas containing a plurality of different removal targets sent from the exhaust apparatus 100 is introduced into the introduction space 17 of the gas treatment apparatus 10. The gas rises, and the removal targets are removed by passing through the first filter 12. Further, by passing through the second filter 15, the removal targets that could not be removed by the first filter 12 are removed. The gas that has passed through the second filter 15 is discharged from the through hole on the upper surface of the housing 11 to the outside of the housing 11 by the blower 26 and returned to the atmosphere at the work site.

[0046] (Method for determining whether the removal target exceeds the threshold value) Next, the determination unit 14 performs a step (S3) of determining whether the concentration of the substance contained in the gas that has passed through the first filter 12 exceeds the threshold value. The operation of the determination unit 14 during the gas treatment will be described with reference to the flowchart of FIG. 5. During the gas treatment, the determination unit 14 acquires the detection value of the concentration of the substance contained in the gas from the first sensor 13 and the detection value of the substance contained in the gas from the second sensor 16 at a predetermined time interval (acquisition step S10).

[0047] Then, the determination unit 14 determines whether the concentration of the substance contained in the gas detected by the first sensor 13 exceeds a threshold value (first determination step S11). If it is below the threshold value, it is determined that the first filter 12 has removed the object to be removed, and the process proceeds to the gas treatment end determination step S15 described later. If it exceeds the threshold value, the determination unit 14 determines that the first filter 12 has broken through with respect to the first object to be removed, and issues an instruction to the alarm unit to issue a first alarm indicating that breakthrough has occurred (alarm instruction step S12). The alarm unit displays the above alarm on the touch panel 27.

[0048] Next, the determination unit 14 determines whether the concentration of the substance contained in the gas detected by the second sensor 16 exceeds a threshold value (second determination step S13). If it exceeds the threshold value, the determination unit 14 determines that the second filter 15 has broken through with respect to the first object to be removed, and issues an instruction to the alarm unit to issue a second alarm (alarm instruction step S14). The alarm unit displays the above alarm on the touch panel 27. Then, the process proceeds to the gas treatment end determination step S15. If it does not exceed the threshold value, the process proceeds to the gas treatment end determination step S15.

[0049] Normally, since the first object to be removed is removed by the first filter 12, the second filter 15 does not adsorb the object to be removed so much, and it is rare for the threshold value to be exceeded in the second determination step S13. However, since the first object to be removed is adsorbed little by little also on the second filter 15, if the second filter 15 is used for a long time, the second filter 15 will break through due to the first object to be removed. For this reason, the second determination step S13 and the alarm instruction step S14 are performed. Note that after the first determination step S11 and the alarm instruction step S12, the process may proceed to the gas treatment end determination step S15 without performing the second determination step S13 and the alarm instruction step S14. Also, the second determination step S13 and the alarm instruction step S14 do not necessarily have to be performed after the first determination step S11 is performed, and may be performed intermittently.

[0050] Next, the determination unit 14 determines whether or not the gas treatment has been completed (gas treatment end determination step S15). A signal indicating the end of the gas treatment is input by the operator from the touch panel 27. If the gas treatment has not been completed, the determination unit 14 returns to step S10 after a predetermined time has elapsed, and repeats the operations of steps S10 to S14. When the gas treatment is completed, the determination unit 14 ends its operation.

[0051] According to the above embodiment, when passing the first filter 12 to remove the object to be removed from the gas, the object to be removed that first breaks through the first filter 12 is specified in advance as the first object to be removed. Then, a threshold value for determining whether or not the first filter 12 has broken through is determined according to the first object to be removed. Therefore, when the first filter 12 has not broken through with respect to the first object to be removed, it can be said that the first filter 12 has not broken through with respect to the objects to be removed other than the first object to be removed. That is, by specifying the first object to be removed that first breaks through the first filter and setting the threshold value, it can be confirmed by the first sensor 13 that all the objects to be removed are below the threshold value, and the concentration of the substances contained in the gas that has passed through the first filter 12 can be detected by the first sensor 13.

[0052] According to the present embodiment, even if it is not necessary to detect the concentration of all the objects to be removed contained in the gas using a detector tube as in the prior art, it is possible to determine whether or not the concentration of the object to be removed exceeds the threshold value, that is, whether or not the first filter has broken through. Therefore, the labor of the operator can be significantly reduced, and the work load can be decreased.

[0053] (Modification example of the method for detecting the object to be removed) When the density detected by the first sensor 13 exceeds the threshold value, the determination unit 14 may perform the following operations. The determination unit 14 calculates the difference between the density detected by the first sensor 13 and the density detected by the second sensor 16. When the difference is smaller than a predetermined value (difference threshold value), it is determined that the first sensor 13 and the second sensor 16 are detecting the density of substances other than the object to be removed. There may be substances in the gas that are substances other than the object to be removed and cannot be adsorbed by the first filter 12 or the second filter 15, and there is a possibility that the first sensor 13 and the second sensor 16 detect the density of such substances. Since such substances pass through the first filter 12 and the second filter 15, the first sensor 13 and the second sensor 16 show almost the same detection value. For this reason, the difference between the density detected by the first sensor 13 and the density detected by the second sensor 16 becomes "0". In actual measurement, the difference does not become "0" due to noise or the like, so a value close to "0" is set as the difference threshold value. When the difference becomes smaller than the difference threshold value, it is determined that substances other than the object to be removed are detected, and whether to issue an alarm by the alarm unit described later, or to alarm that there is a possibility that substances other than the object to be removed are detected.

[0054] As described above, one embodiment of the present invention has been explained. However, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. Also, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. For example, expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states where there are tolerances or relative displacements with angles and distances that can obtain the same function. For example, expressions indicating that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent states where there are tolerances or differences that can obtain the same function. For example, expressions indicating shapes such as a rectangular shape or a cylindrical shape not only represent shapes such as a rectangular shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. The expressions "comprising", "including", "having", or "possessing" one component are not exclusive expressions that exclude the existence of other components.

Explanation of Reference Numerals

[0055] 10 Gas treatment device 11 Housing 11b Vent hole 12 First filter 12a to 12e Members constituting the first filter 13 First sensor 14 Determination unit 15 Second filter 16 Second sensor 17 Gas introduction space 19 First suction pipe 19e Through hole 21 Control device 23 Second suction pipe 100 Exhaust device

Claims

1. A gas treatment device that passes gas and removes a plurality of removal targets of different types among the substances contained in the gas, comprising: a first filter that removes a removal target by passing the gas; a first sensor for detecting the concentration of the substance contained in the gas that has passed through the first filter; a determination unit that determines whether the concentration of the substance detected by the first sensor exceeds a set threshold value; the threshold value is set to be equal to or less than one-tenth of the control concentration of the first removal target; the first removal target is a removal target that first breaks through the first filter when the first filter is passed to remove the removal target from the gas.

2. The gas treatment device according to claim 1, further comprising an alarm unit that issues an alarm when the determination unit determines that the concentration of the substance contained in the gas exceeds the threshold value.

3. The gas treatment device according to claim 1 or 2, further comprising a second filter through which the gas that has passed through the first filter passes.

4. The gas treatment device according to claim 3, further comprising a second sensor for detecting the concentration of the substance contained in the gas that has passed through the second filter.

5. A method for detecting a removal target by a gas treatment device that passes gas and removes a plurality of removal targets of different types among the substances contained in the gas, comprising: identifying a first removal target that first breaks through the first filter when the first filter is passed to remove the removal target from the gas, and determining a threshold value according to the first removal target; performing a gas treatment step of removing the removal target from the gas by passing the gas through the first filter; determining whether the concentration of the substance contained in the gas that has passed through the first filter exceeds the threshold value.

Images