Smoke detector

Abstract

A smoke sensor is provided that does not misdetect incoming dust as smoke when the filter for capturing dust is removed or moved. The smoke sensor (11) includes a light-emitting part (111) and a light-receiving part (113) disposed in a sensing area (S1). The light emitted by the light-emitting part (111) is scattered by particles contained in the air flowing into the sensing area (S1) from the outside space. The light-receiving part (113) receives the scattered light to determine whether the air contains smoke, and senses the generation of smoke in the outside space based on the determination result. The smoke sensor (11) includes: a filter (116) for capturing and removing dust contained in the air flowing into the sensing area (S1) from the outside space; an openable and closable cover (1102) for separating the receiving space for accommodating the filter (116) from the outside; and a switch (117) for detecting the installation and removal of the filter (116). The control unit (118) stops the smoke detection operation after the switch (117) has detected that the filter (116) has been removed.

Description

[Technical Field]

[0001] This invention relates to a technology for sensing smoke. [Previous Technology]

[0002] There is a smoke detector that detects the occurrence of smoke in the external space by sensing the particles contained in the air flowing into the sensing area from the external space.

[0003] When dust-laden air flows into the smoke-sensing area of ​​a smoke sensor, there is a risk that the smoke sensor may mistake the dust for smoke particles. Therefore, most smoke sensors have a filter in the airflow path from the outside space into the sensing area to capture dust particles contained in the air.

[0004] Patent document 1 is one example of a patent document that discloses a smoke sensor equipped with a filter. Patent document 1 describes a smoke sensor device in which a suction unit, a detection unit, and a filter unit can be individually assembled and detached from a housing. The suction unit draws in outside air, the detection unit detects smoke particles from the drawn-in outside air, and the filter unit consists of a filter for removing dust from the drawn-in outside air and a housing surrounding the filter.

[0005] The smoke detection device described in Patent Document 1 is easy to identify, maintain, and replace the faulty part.

[0006] Furthermore, most smoke detectors have a housing, and within the housing, there is a space for sensing particles. Most smoke detectors also have an openable and closable cover so that operators can check the status of components inside the housing or replace them for maintenance or other purposes.

[0007] Patent document 2 discloses a smoke sensor with an openable and closable cover. Patent document 2 describes a photoelectric smoke sensor having an optical case, a laser light source, a light receiving element, and a fire detection unit. The optical case blocks light from the outside, the laser light source emits light inside the optical case, the light receiving element receives the scattered light emitted from the laser light source by smoke particles present in the smoke detection unit, and the fire detection unit determines that a fire is occurring when the level of the output signal of the light receiving element is above a threshold value.

[0008] The smoke detector described in Patent Document 2 has an optical housing comprising a casing and an openable and closable optical cover that blocks the opening of the casing. Furthermore, the smoke detector described in Patent Document 2 is characterized by including a control unit that, when the optical cover is opened, stops the emission of light from the laser source or makes the emission period from the laser source longer than when the cover is closed. The smoke detector described in Patent Document 2, with this configuration, can avoid the danger of laser light entering the eyes of the operator opening the optical cover and causing eye pain. [Prior Art Documents] [Patent Documents]

[0009] Patent Document 1: Japanese Patent Application Publication No. 2008-108140; Patent Document 2: Japanese Patent Application Publication No. 2010-237738 [Summary of the Invention]

[0010] [The problem that the invention aims to solve]

[0011] When the operator temporarily removes the filter for purposes such as replacing the filter or inspecting other parts, dust-laden air flows into the sensing area without passing through the filter. Furthermore, when the operator opens the cover covering the filter for inspecting components within the smoke sensor, the filter, which had previously blocked the airflow path through the cover, may become loose, shifting from its functional position and allowing dust-laden air to flow into the sensing area through the gap. As a result, there is a risk that the smoke sensor may mistake dust for smoke.

[0012] In view of the above, the present invention provides a smoke detector that will not misdetect incoming dust as smoke when the dust-capturing filter is removed or shifted. [Means for Solving the Problem]

[0013] To solve the above-mentioned problems, the present invention proposes a smoke detector that detects the generation of smoke in the external space by sensing particles contained in the air flowing into the sensing area from the external space. The detector comprises: a sensing means for sensing particles in the air within the sensing area and sensing smoke based on the sensing results; a filter disposed in the airflow path into the sensing area and capturing dust contained in the air; a loading / unloading detection means for detecting the loading / unloading of the filter; and a control means for stopping at least a portion of the operation of the sensing means for sensing smoke when the loading / unloading detection means detects that the filter has changed from an installed state to a removed state. [Effects of the Invention]

[0014] According to the present invention, since the smoke sensing will stop after the filter that captures dust is removed or shifted, the incoming dust will not be falsely sensed as smoke.

Implementation Method

[0016] [Implementation Form]

[0017] The following describes a smoke detection system 1 according to one embodiment of the present invention. FIG1 is a diagram showing the configuration of the smoke detection system 1. The smoke detection system 1 includes a smoke sensor 11 and an upper system 12.

[0018] The smoke sensor 11 is a device that is disposed in the space of the monitored object where smoke occurs (hereinafter referred to as the "monitoring space"), and takes in the air in the monitoring space. As long as the air taken in contains smoke, it will detect the smoke, and when smoke is detected, it will send a smoke alarm to the higher system 12.

[0019] In Figure 1, although the number of smoke sensors 11 in the smoke detection system 1 is one, the number of smoke sensors 11 in the smoke detection system 1 varies depending on the number or width of the monitored space.

[0020] The high-level system 12 may also be any one of a monitoring terminal device, a smoke alarm panel, a central monitoring system, etc. The high-level system 12 and the smoke sensor 11 can communicate with each other through a wired, wireless, or hybrid communication medium and can communicate with each other via data.

[0021] Since the higher-order system 12 is the same as the higher-order system of the prior art, its description is omitted.

[0022] FIG2 is a schematic diagram showing the configuration of the smoke sensor 11. FIG2(a) schematically shows the smoke sensor 11 with the filter 116 installed (hereinafter referred to as "installed state") and the cover 1102 closed (hereinafter referred to as "closed state"), and FIG2(b) schematically shows the smoke sensor 11 with the filter 116 removed (hereinafter referred to as "removed state") and the cover 1102 open (hereinafter referred to as "open state").

[0023] The smoke detector 11 includes a housing 110, a light-emitting part 111, a light-emitting part 112, a light-receiving part 113, a lens 114, a fan 115, a filter 116, a switch 117, and a control unit 118.

[0024] The housing 110 is a container that forms a space inside. In the example of FIG2, the housing 110 has a partition 1101 that divides the internal space into a sensing area S1, which is a region for sensing smoke, and a receiving area S2 for accommodating the control unit 118.

[0025] Furthermore, the wall portion forming the sensing area S1 in the housing 110 is provided with an air intake port P and an air exhaust port Q. The air intake port P is an opening that functions as an inlet for air to flow from the external space into the internal space, and the air exhaust port Q is an opening that functions as an outlet for air to flow from the internal space into the external space.

[0026] Furthermore, a portion of the wall of the housing 110 is a cover 1102 that can be opened and closed. The operator opens the cover 1102 to inspect and replace the internal parts of the smoke sensor 11. Moreover, in the example of Figure 2, although the air intake P is provided on the cover 1102, the air intake P can also be provided on the wall of the housing 110 outside the cover 1102.

[0027] The light-emitting part 111 and the light-receiving part 112 are equipped with, for example, LEDs, and emit light from the LEDs under the control of the control unit 118. The light emitted by the light-emitting part 111 is used to sense smoke within the sensing area S1. The light-emitting part 111 emits light facing the airflow path from the intake port P to the exhaust port Q. Furthermore, the light-emitting part 111 is positioned so as not to face the light-receiving part 113, so as to prevent the emitted light from directly incident on the light-receiving part 113.

[0028] On the other hand, the light emitted by the light-emitting unit 112 is used to measure the dirt on the lens 114. The light-emitting unit 112, as viewed from the light-receiving unit 113, is positioned along the airflow path from the intake port P to the exhaust port Q, and emits light in a direction that directly incidents on the light-receiving unit 113. Furthermore, for example, the distance from the light-emitting unit 112 to the light-receiving unit 113 is shorter than the distance from the light-emitting unit 111 to the light-receiving unit 113. Therefore, the light emitted from the light-emitting unit 112 and directed towards the light-receiving unit 113 has less influence from particles in the air flowing into the sensing area S1 compared to the light emitted from the light-emitting unit 111 and directed towards the light-receiving unit 113.

[0029] The light receiving unit 113 has, for example, a photodiode, and receives the scattered light from the light irradiated by ...

[0030] The lens 114 concentrates a portion of the light emitted from the light-emitting part 111 and the light-emitting part 112 and guides it to the light-receiving part 113.

[0031] The fan 115 operates under the control of the control unit 118 and performs the following tasks: by rotating the blades, it generates the flow of air that flows from the external space into the sensing area S1 through the air intake port P and flows out into the external space through the exhaust port Q.

[0032] The filter 116 comprises a cylindrical housing and a filter body disposed within the housing. The filter 116 is disposed in the airflow path from the intake port P to the exhaust port Q. The filter body captures dust contained in the air flowing from the external space to the sensing area S1 and prevents dust from entering the sensing area S1. Furthermore, the cover 1102 is an openable and closable cover that separates the housing space containing the filter 116 (in this case, the space between the fan 115 and the cover 1102) from the outside and performs the following function: by maintaining the filter 116 in the installed state in the closed state, the filter 116 performs its function.

[0033] Switch 117 (an example of a loading / unloading detection means) is a component that performs the task of detecting the loading / unloading of filter 116, i.e., its installed and unloaded states. Switch 117 has a button 1171 that is pressed in the direction facing filter 116. Switch 117 outputs an installation signal to control unit 118 when filter 116 is in the installed state and button 1171 is pressed, and outputs a unloading signal to control unit 118 when filter 116 is in the unloaded state and button 1171 is not pressed. Hereinafter, the installation signal and the unloading signal will be referred to together as the loading / unloading signal.

[0034] The control unit 118 is a device for controlling the operation of the smoke sensor 11. The hardware of the control unit 118 is, for example, a computer, and the control unit 118 is implemented by the computer performing processing according to the program used by the control unit 118.

[0035] Figure 3 is a diagram showing the configuration of the computer 10, which is used as the hardware of the control unit 118. The computer 10 includes: a processor 101 for performing various data processing; a memory 102 for storing various data; an input / output interface 103 for receiving and transmitting signals with components such as the light-emitting part 111 of the smoke sensor 11; and a communication interface 104 for sending and receiving data with external devices (in this case, the high-level system 12).

[0036] Figure 4 is a diagram showing the functional configuration of the control unit 118. That is, the control unit 118, which has the configuration shown in Figure 4, is implemented by the computer 10 performing processing according to the program used by the control unit 118. The functional configuration of the control unit 118 will be described below.

[0037] The light-emitting indicator 1181 is used to instruct the light-emitting part 111 to emit light. The light-emitting indicator 1181 instructs the light-emitting part 111 to emit light each time, for example, a predetermined time elapses, after the smoke sensor 11 has stopped due to an instruction from the control means 1180 (described later) until the instruction to stop has resumed.

[0038] The light-emitting indicator 1182 is used to instruct the light-emitting part 112 to emit light. The light-emitting indicator 1182 instructs the light-emitting part 112 to emit light during the period from when the commanded action stops due to the instruction from the control means 1180 described later until the commanded action restarts, so that the light-emitting part 112 emits light each time, for example, a predetermined time has elapsed.

[0039] The light intensity signal acquisition means 1183 acquires the light intensity signal output from the light receiving unit 113.

[0040] The smoke detection means 1184 determines whether smoke exists in the air around the smoke sensor 11 by judging whether the intensity of the light intensity signal obtained by the light intensity signal acquisition means 1183 meets the predetermined conditions for smoke detection. The predetermined conditions for smoke detection, for example, refer to the condition that the light intensity signal remains within the reference range indicating the presence of smoke for a predetermined time or longer.

[0041] The intensity of light received by the light-receiving part 113 is affected by the degree of dirtiness of the lens 114. Therefore, the smoke detection means 1184 is used to adjust the conditions (e.g., reference range) for smoke detection based on the degree of dirtiness of the lens 114 measured by the dirtiness measurement means 1185.

[0042] The smoke detection method 1184 generates smoke occurrence notification data when it detects the presence of smoke. The smoke occurrence notification data generated by the smoke detection method 1184 is sent to the higher-level system 12 via the communication method 1186.

[0043] Furthermore, the smoke detection means 1184 uses different conditions (e.g., a different reference range than usual) during the period when the light source 112 illuminates the light used for dirt measurement, thereby continuing to sense smoke even while dirt measurement is being performed. However, if the time when the light source 112 illuminates the light used for dirt measurement is short enough that no problem will actually occur even if smoke sensing is not performed during that period, the smoke detection means 1184 may also stop sensing smoke during the period when the light source 112 illuminates the light used for dirt measurement.

[0044] The light-emitting indicator 1181, the light-emitting part 111, the light-receiving part 113, the light intensity signal acquisition means 1183, and the smoke detection means 1184 are configured to sense particles in the air within the sensing area S1 and to sense smoke based on the sensing results.

[0045] The dirt measurement means 1185 measures the dirtiness of the lens 114 by measuring the change in light intensity shown by the light intensity signal obtained by the light intensity signal acquisition means 1183 when the light-emitting part 112 changes from a non-light-emitting state to a light-emitting state. The dirt measurement means 1185, for example, stores data indicating the correspondence between the degree of dirtiness of the lens 114 and the degree of change in light intensity received by the light-receiving part 113 when the light-emitting part 112 is off and when it is lit due to dirtiness, and measures the degree of dirtiness of the lens 114 by referring to this data.

[0046] The dirt measurement means 1185 generates dirt notification data that indicates the degree of dirt measured. The dirt notification data generated by the dirt measurement means 1185 is sent to the higher-level system 12 via communication means 1186. Furthermore, as described above, the dirt notification data generated by the dirt measurement means 1185 is also used by the smoke determination means 1184 to adjust the conditions for smoke detection.

[0047] Furthermore, if the smoke detection means 1184 stops processing for sensing smoke while the light-emitting part 112 is illuminating the light used for dirt measurement, the light-emitting indication means 1182 can indicate to the light-emitting part 111 to stop illuminating during this period, and the dirt measurement means 1185 can measure the degree of dirt on the lens 114 by only receiving the light intensity measured by the light-receiving part 113 after receiving the light illuminating from the light-emitting part 112.

[0048] The light-emitting indicator 1182, the light-emitting part 112, the light-receiving part 113, the light intensity signal acquisition means 1183, and the dirt measurement means 1185 constitute a dirt detection means for detecting dirt within the detection sensing area S1.

[0049] The communication means 1186 is used to send and receive various data with the higher-level system 12. For example, as described above, the communication means 1186 sends the smoke generation notification data generated by the smoke determination means 1184 and the dirt notification data generated by the dirt measurement means 1185 to the higher-level system 12.

[0050] Users of the advanced system 12 (e.g., administrators of the smoke detection system 1) can use smoke occurrence notification data sent from the smoke detector 11 to know that there is a higher probability of a fire occurring in the monitored space where the smoke detector 11 is installed. Furthermore, users of the advanced system 12 can use dirt notification data sent from the smoke detector 11 to know the degree of dirt on the lens 114 of the smoke detector 11, and can rely on operators to clean the lens 114 as needed.

[0051] Loading / unloading signal acquisition means 1187 acquires loading / unloading signals from switch 117. Operation indication means 1188 indicates the start and end of operation of fan 115.

[0052] The timing means 1189, for example, continuously measures the current time based on a clock signal generated by the clock provided by the processor 101, and generates a time signal indicating the measured current time.

[0053] Control means 1180 controls the operation of light-emitting indicator means 1181, light-emitting indicator means 1182, smoke detection means 1184, dirt detection means 1185 and operation indicator means 1188.

[0054] The control means 1180 is used to stop or restart the indication action of the light indicator means 1181, etc., when the loading and unloading signal received from the switch 117 through the loading and unloading signal acquisition means 1187 changes, accompanying the loading and unloading of the filter 116 by the operator.

[0055] Figure 5 is a flowchart showing the processing performed by the control means 1180 after the loading and unloading signal changes.

[0056] Control means 1180 determines, when a change in the loading / unloading signal is detected, whether the change indicates a change from the installation signal to the unloading signal or a change from the unloading signal to the installation signal (step S101).

[0057] In step S101, if it is determined that the change in the loading / unloading signal indicates a change from the installation state to the unloading state (step S101; "1"), the control means 1180 performs the following processing (step S201). (1) For the light-emitting indicator means 1181, the light-emitting indication to the light-emitting part 111 is prohibited. (2) For the light-emitting indicator means 1182, the light-emitting indication to the light-emitting part 112 is prohibited. (3) For the smoke detection means 1184, the processing used for smoke detection is ordered to stop. (4) For the dirt detection means 1185, the processing used for dirt detection is ordered to stop. (5) For the operation indicator means 1188, the operation of the fan 115 is ordered to stop.

[0058] During the processing of the control means 1180 in step S201, the light-emitting units 111 and 112 do not emit light, and the fan 115 stops rotating its blades. Furthermore, the communication means 1186 does not transmit smoke generation notification data or dirt notification data to the higher-order system 12.

[0059] When the processing of step S201 is completed, the control means 1180 ends the processing according to the flow of Figure 5.

[0060] In step S101, if it is determined that the change in the loading / unloading signal indicates a change from the unloading state to the installation state (step S101; "2"), the control means 1180 first instructs the operation indication means 1188 to restart the operation of the fan 115 (step S301). Accompanying the processing of the control means 1180 in step S301, the fan 115 restarts the rotation of its blades.

[0061] Next, the control means 1180 determines whether a predetermined time (e.g., 1 minute) has elapsed (step S302). If it is determined in step S302 that the predetermined time has not elapsed (step S302; "No"), the control means 1180 repeats the determination in step S302.

[0062] The time until the determination in step S302 becomes "yes" after step S301 has been executed refers to the time taken for the airflow generated by fan 115 to expel the dust that has entered the sensing area S1 from the air intake P to the outside. That is, even after the filter 116 is removed by the operator, air containing dust may flow into the sensing area S1. Even in such cases, when the filter 116 is installed, the fan 115 will operate for a predetermined time before the smoke detection processing performed by the smoke detection means 1184 is restarted, so the dust that has entered the sensing area S1 will still be expelled.

[0063] In step S302, if it is determined that the predetermined time has elapsed (step S302; "Yes"), the control means 1180 performs the following processing (step S303). (1) For the light-emitting indicator means 1181, light emission indication to the light-emitting unit 111 is allowed. (2) For the light-emitting indicator means 1182, light emission indication to the light-emitting unit 112 is allowed. (3) For the smoke detection means 1184, the processing for smoke detection is ordered to restart. (4) For the dirt detection means 1185, the processing for dirt detection is ordered to restart.

[0064] Accompanying the processing of the control means 1180 in step S303, the light-emitting units 111 and 112 resume emitting light, the smoke detection means 1184 resumes the processing for smoke detection, and the dirt detection means 1185 resumes the processing for dirt detection. Then, if smoke has occurred in the monitored space, smoke occurrence notification data is sent to the higher-level system 12 via the communication means 1186, and if dirt detection has been performed, dirt notification data is sent to the higher-level system 12 via the communication means 1186.

[0065] According to the smoke detection system 1 described above, even if the operator removes the filter 116, there will be no false smoke detection or false measurement of dirt due to dust intruding into the sensing area S1.

[0066] Furthermore, according to the smoke detection system 1 described above, only the fan 115 will restart after the operator installs the filter 116, and the smoke detection or dirt measurement will restart after the dust has been discharged from the sensing area S1. Therefore, after the filter 116 is installed, there will be no false smoke detection or false dirt measurement due to dust floating in the sensing area S1.

[0067] [Variations] The above-described embodiments are specific examples of the present invention, and various variations can be made within the scope of the technical concept of the present invention. Examples of such variations are shown below. Furthermore, two or more variations shown below can also be appropriately combined.

[0068] (1) In the above embodiment, the loading and unloading of filter 116 is detected directly by switch 117. Alternatively, the loading and unloading of filter 116 may be detected indirectly.

[0069] Figure 6 is a schematic diagram showing the configuration of one example of such a modified smoke sensor 11. The smoke sensor 11 shown in Figure 6 does not directly detect the installation or removal of the filter 116 by the switch 117, but indirectly detects the installation or removal of the filter 116 by detecting the opening and closing of the cover 1102 covering the filter 116. This is different from the smoke sensor 11 in the above embodiment.

[0070] That is, in this variation, the button 1171 of the switch 117 is pressed in the direction toward the cover 1102. Then, while the cover 1102 is in the closed state and the button 1171 is pressed, the switch 117 outputs an installation signal to the control unit 118 indicating that the filter 116 is firmly held in the predetermined position by the cover 1102. On the other hand, while the cover 1102 is in the open state and the button 1171 is not pressed, the switch 117 outputs a removal signal to the control unit 118 indicating that the filter 116 is not held by the cover 1102 and that the filter 116 may deviate from the predetermined position.

[0071] In other words, in this variation, the switch 117 (an example of a loading and unloading detection method) detects the open state of the cover 1102 as the state after the filter 116 has been removed, and detects the closed state of the cover 1102 as the state after the filter 116 has been installed.

[0072] According to this variation, even if, for example, the cover 1102 is opened and the filter 116 is shifted, there will be no false detection of smoke or false measurement of dirt due to dust intruding into the sensing area S1.

[0073] (2) In the above embodiment, the means of detecting the loading and unloading of the detection filter 116 is a switch 117. The type of means of detecting the loading and unloading of the detection filter 116 is not limited to a switch. For example, an object detection sensor using light can also be used as a means of detecting the loading and unloading of the detection filter 116.

[0074] (3) In the above embodiment, when the change from the installed state to the removed state of the filter 116 has been detected, the control means 1180 stops all the light emission performed by the light-emitting unit 111, the light emission performed by the light-emitting unit 112, the smoke detection processing performed by the smoke detection means 1184, the dirt detection processing performed by the dirt detection means 1185, and the operation of the fan 115. When the change from the installed state to the removed state of the filter 116 has been detected, the control means 1180 does not need to stop all of these, but only needs to stop at least a part of the smoke detection operation.

[0075] For example, if the light emitted by the light-emitting part 111 or the light-emitting part 112 is not dangerous even if it enters the operator's eyes, the control means 1180 may not prohibit the light-emitting indication to the light-emitting part 111 by the light-emitting indication means 1181, or may not prohibit the light-emitting indication to the light-emitting part 112 by the light-emitting indication means 1182.

[0076] (4) In the above embodiment, when the change from the removed state of the filter 116 to the installed state has been detected, the control means 1180 first instructs the fan 115 to restart operation, and only for a predetermined time retains the restart of all the light emission performed by the light-emitting unit 111, the light emission performed by the light-emitting unit 112, the smoke detection processing performed by the smoke detection means 1184, and the dirt detection processing performed by the dirt detection means 1185. Alternatively, when the change from the removed state of the filter 116 to the installed state has been detected, the control means 1180 may also, at the same time as instructing the fan 115 to restart operation, allow light emission indication to the light-emitting unit 111 by the light-emitting indicator means 1181, or allow light emission indication to the light-emitting unit 112 by the light-emitting indicator means 1182.

[0077] (5) In the above embodiment, although the hardware of the control unit 118 is assumed to be a computer, the control unit 118 may also be configured as a special device having integrated circuits such as ASIC (Application Specific Integrated Circuit) and FPGA (Field Programmable Gate Array). [Simplified Explanation of the Diagram]

[0015] [Figure 1] is a diagram showing the configuration of a smoke detection system according to an embodiment. [Figure 2] is a diagram schematically showing the configuration of a smoke sensor according to an embodiment. [Figure 3] is a diagram showing the configuration of a computer, which is used as the hardware of a control unit according to an embodiment. [Figure 4] is a diagram showing the functional configuration of a control unit according to an embodiment. [Figure 5] is a diagram showing the flow of processing performed by a control means according to an embodiment after a change in loading / unloading signal. [Figure 6] is a diagram schematically showing the configuration of a smoke sensor according to a variation example.

Claims

1. A smoke detector that senses the occurrence of smoke in the external space by sensing particles contained in air flowing into a sensing area from an external space, comprising: a sensing means for sensing particles in the air within the sensing area and sensing smoke based on the sensing result; a filter disposed in the flow path of the air flowing into the sensing area and capturing dust contained in the air; a loading / unloading detection means for detecting the loading / unloading of the filter; and a control means for stopping the smoke sensing performed by the sensing means when the loading / unloading detection means detects that the filter has changed from an installed state to an unloaded state.

2. The smoke detector as described in claim 1, wherein, It has: a cover that can be opened and closed, which separates the receiving space for accommodating the aforementioned filter from the outside; the aforementioned loading and unloading detection means detects the open state of the aforementioned cover as the state after the aforementioned filter has been removed, and detects the closed state of the aforementioned cover as the state after the aforementioned filter has been installed.

3. The smoke detector as described in claim 1, wherein, It is equipped with: a dirt detection means that detects dirt in the aforementioned sensing area; and a control means that stops the operation of the aforementioned dirt detection means when the aforementioned installation and removal detection means detects that the aforementioned filter has changed from the installed state to the removed state.

4. The smoke detector as described in claim 1, wherein, The aforementioned sensing means has a light-emitting part that emits light; the aforementioned control means stops the light emission by the aforementioned light-emitting part when the aforementioned installation and removal detection means detects that the aforementioned filter has changed from the installed state to the removed state.

5. The smoke detector as described in claim 1, wherein, It includes: a fan that generates airflow from the outside toward the aforementioned sensing area; and a control means that stops the operation of the aforementioned fan when the aforementioned installation and removal detection means detect that the aforementioned filter has changed from an installed state to a removed state.

6. The smoke detector as described in claim 1, wherein, It includes: a fan that generates airflow from the outside toward the aforementioned sensing area; a control means that stops the operation of the aforementioned fan when the aforementioned installation / removal detection means detects that the aforementioned filter has changed from an installed state to a removed state; and a control means that, when the aforementioned installation / removal detection means detects that the aforementioned filter has changed from a removed state to an installed state, restarts the operation of the aforementioned fan, and after a predetermined time, restarts the aforementioned sensing means to sense the stopped smoke.

7. The smoke detector as described in claim 3, wherein, It includes: a fan that generates airflow from the outside toward the aforementioned sensing area; a control means that stops the operation of the aforementioned fan when the aforementioned installation / removal detection means detects that the aforementioned filter has changed from an installed state to a removed state; and a control means that, when the aforementioned installation / removal detection means detects that the aforementioned filter has changed from a removed state to an installed state, restarts the operation of the aforementioned fan, and after a predetermined time, restarts the operation of the aforementioned dirt detection means from being stopped.

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