TW202307798A - smoke detector - Google Patents

Abstract

The purpose of the present invention is to reduce the inexpedience in which a smoke detector that generates log data indicating measured values from a flow meter generates unwanted log data indicating substantially the same values. A flow meter 115 measures the flow rate of air flowing into a sensing area of the smoke detector from an external space. A flow rate signal acquisition means 183 included in a control unit 118 provided in the smoke detector acquires a flow rate signal indicating a measured value from the flow meter 115, and a storage means 1180 temporarily stores the flow rate signal in a flow rate temporary storage table. A log generation means 1184, upon determining that the rate of change in the measured values of the flow rate stored in the flow rate temporary storage table has reached a set airflow change step value, generates log data indicating the measured value of the flow rate at that point in time, and the storage means 1180 adds the log data to a flow rate log table. A threshold changing means 1187 changes the set airflow change step value in response to a prescribed operation performed by a user on a button 116.

Description

smoke detector

The present invention relates to a technology for sensing smoke.

There is a smoke detector that senses the occurrence of smoke in an external space by sensing particles contained in air flowing from the external space into a sensing area.

For example, a smoke detector called a photoelectric smoke detector emits light from a light-emitting element to a sensing area, and receives the light from particles in the air in the sensing area through a light-receiving element. The reflected scattered light is then used to sense the particles contained in the air flowing into the sensing area from the external space according to the intensity of the light received and measured by the light receiving element, thereby sensing the occurrence of smoke in the external space.

As a patent document disclosing the technology of a photoelectric smoke detector, there is Patent Document 1, for example. The photoelectric smoke detection sensor described in Patent Document 1 proposes the following inventions: when particles of smoke other than hot gas flow into the smoke detection space (sensing area), and when smoke flows into the smoke detection space Next, the point of attention is that the output signal of the light-receiving element changes with time in a different way, and the output signal output from the light-receiving element is only delayed by a predetermined delay time, so as to avoid false detection of smoke due to the occurrence of heat, etc. missing. [Prior Art Literature] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2019-61423

[Problem to be Solved by the Invention]

Like a photoelectric smoke detector, a smoke detector (hereinafter, simply referred to as "" Smoke detector"), mostly to prevent dust with a particle size larger than smoke particles from flowing into the sensing area and attaching to the light-emitting element, light-receiving element, etc. in the form of dirt. On the air flow path of the area, there is a filter (filter) with a mesh thickness that allows smoke to pass through but dust cannot pass through. When the filter is clogged or damaged for some reason, the photoelectric smoke detector cannot correctly sense the smoke generated in the external space. In addition, dust and the like may adhere to the inner wall of a pipe or the like forming a flow path of air from the external space toward the sensing area, and may obstruct the flow of air. In this case, the photoelectric smoke detector cannot correctly sense the smoke that occurs in the external space.

In order to detect occurrence of the above-mentioned abnormality, the following mechanism may be considered: install a flow meter for measuring the air flow flowing into the sensing area from the external space, and monitor whether the air flow measured by the flow meter is within an appropriate range. In such a mechanism, the data representing the measurement results of the flowmeter are memorized as log data, and the change with time of the air flow rate is analyzed, thereby making it possible to estimate when the air flow rate has become out of the appropriate range The reason for this is the time when the air flow rate is estimated to be out of the appropriate range.

For example, if the measurement results of the flowmeter are memorized as log data every time a predetermined time elapses, log data showing substantially the same value during a period in which the air flow rate hardly changes will be wasted. For example, when the recorded data is stored in the smoke detector, it is not good to memorize whether there is any useful recorded data in the memory area with a limited capacity. Also, when the recorded data is sent from the smoke detector to the upper system and stored in the upper system, the amount of data communication will increase due to useless recorded data, which is not preferable. Also, when there are many recorded data substantially showing the same value when the maintenance staff etc. check the recorded data, wasted time will be spent on the confirmation work, which is not preferable.

Therefore, each time the rate of change of the flow rate measured by the flowmeter (the absolute value of the change amount from the flow rate after the last record data is generated, divided by the value obtained by the flow rate after the last record data generation) reaches a predetermined limit A new record data is generated when it is valued, thereby reducing the loss of useless record data. Hereinafter, the threshold value of the rate of change of the flow rate used as a condition for generating recorded data is referred to as an "airflow change step (step) value".

However, the rate of change of the air flow flowing from the external space into the sensing area of the smoke detector is often different depending on whether the flow is low flow or high flow. For example, the lower the flow rate is, the larger the rate of change of the flow rate will be taken even if the change of the flow rate is small. Therefore, when the flow rate is low, the rate of change reaches the air flow change step value frequently, and useless recorded data is lost.

In view of such circumstances, the present invention provides a means for a smoke sensor that can generate recorded data representing the measured value of a flowmeter to reduce the absence of useless recorded data that substantially represents the same value. [Means to solve the problem]

In order to solve the above-mentioned problems, the present invention proposes a smoke detection sensor, which senses the smoke detection in the aforementioned external space by sensing the particles contained in the air flowing into the sensing area from the external space. A measuring device, which has: flow measuring means, which measures the flow of air; and record generating means, which generates record data indicating the measured value when the rate of change of the measured value of the aforementioned flow measuring means has reached a limit value; and the limit The value changing means is to change the aforementioned limit value. [Invention effect]

According to the present invention, the air flow change step value is changed to an appropriate value in response to the air flow flowing into the sensing area from the external space, thereby generating recorded data representing the measured value of the flow measuring means at an appropriate frequency. As a result, the absence of recorded data which yields substantially the same value can be reduced.

[implementation form]

A smoke detector 1 according to an embodiment of the present invention will be described below. FIG. 1 is a diagram showing the composition of a smoke detection sensing system 1 . The smoke detection sensing system 1 is equipped with a smoke detection sensor 11 and a high-level system 12 .

The smoke detection sensor 11 is arranged in the monitoring object space where smoke occurs (hereinafter referred to as "surveillance space"), and takes in the air in the monitoring space, as long as the taken-in air contains smoke The smoke is sensed and, if smoke is sensed, an alarm of smoke occurrence is sent to devices of the higher level system 12 .

In FIG. 1 , although the number of smoke detection sensors 11 provided in the smoke detection sensing system 1 is one, the number of smoke detection sensors 11 provided in the smoke detection sensing system 1 corresponds to the number of monitoring spaces. or width changes.

The high-level system 12 may be any of a monitoring terminal device, a smoke alarm panel, a central monitoring system, and the like. The high-level system 12 and the smoke detector 11 can be communicated and connected through wired, wireless, or mixed communication media, and can communicate with each other.

Since the high-level system 12 is the same as the high-level system of the prior art, its description is omitted.

FIG. 2 is a diagram schematically showing the configuration of the smoke detector 11 . The smoke detector 11 includes a housing 110 , a light emitting unit 111 , a light receiving unit 112 , a fan 113 , a filter 114 , a flow meter 115 , a button 116 , a light emitting unit 117 and a control unit 118 .

The casing 110 is a container forming a space inside. The casing 110 has: an air inlet P, which is an opening functioning as an inlet for air to flow into the inner space from the outer space; The opening of the exit function.

In addition, the housing 110 has: a wall 1101, which is used to form a sensing area S in the inner space as an area for sensing smoke; and a pipe 1102, which is formed from the suction port P to the sensing area S. a flow path of air in the region S; and a pipe 1103 that forms a flow path of air from the sensing region S to the exhaust port Q.

The light emitting unit 111 has, for example, an LED, and emits light from the LED to the sensing area S. As shown in FIG. The light receiving part 1112 is arranged at a position not facing the light emitting part 111 so that the light emitted from the light emitting part 111 does not directly enter, but the scattered light scattered by the particles in the air in the sensing area S enters. . The light receiving part 112 has, for example, a photodiode for receiving part of the scattered light in the sensing region S, and outputs a light intensity signal representing the intensity of the received light.

The fan 113 is arranged on the air flow path formed by the duct 1102, and performs the following task: the air flow from the external space toward the sensing area S is generated by the rotating blades.

The filter 114 is disposed on the air flow path formed by the pipe 1102 to capture the dust contained in the air from the external space toward the sensing area S, and prevent the dust from entering the sensing area S.

The flow meter 115 (an example of flow measurement means) is a sensor (sensor) that measures the flow of air flowing into the sensing area S from the external space by the operation of the fan 113 . The flow meter 115 includes, for example, a thermistor, and specifies the air flow rate based on the resistance value of the thermistor that changes with the air flow rate. However, the method for measuring the flow rate of the air by the flowmeter 115 is not limited thereto, and various known flowmeters may also be used as the flowmeter 115 .

The button 116 (an example of an operation acceptance means) is an operation element that accepts an operation from a user (for example, a manager of the smoke sensor 1, etc.). The button 116 is operated when the user changes the set air flow change step value (an example of the limit value).

The light emitting unit 117 is a component unit performing a task of notifying the user that the user's operation on the button 116 has been accepted. The light-emitting part 117 has, for example, an LED, and in response to the operation of the button 116 by the user, it will be in a different manner corresponding to the set value of the airflow change step value, such as when the airflow change step value is set to 10%. It emits light once, emits light twice when it is set to 20%, and emits light three times when it is set to 30%, thereby notifying the user of the set value.

In FIG. 2 , although the button 116 and the light emitting part 117 are arranged on the outer side of the housing 110, the arrangement positions of the button 116 and the light emitting part 117 are not limited thereto. For example, in the case where the housing 110 has a cover that can be opened and closed, a button 116 may be arranged at a position that the user can press when the cover is opened in the internal space of the housing 110, In addition, in the inner space of the casing 110 , the light emitting part 117 is disposed at a position that can be recognized by the user when the cover is opened. In this case, it is possible to avoid the fact that the set value of the air flow change step value is changed by an operation not intended by the user.

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

FIG. 3 is a diagram showing the configuration of the computer 10 employed as the hardware of the control unit 118 . The computer 10 is provided with: a processor (processor) 101, which processes various data; and a memory (memory) 102, which stores various data; Signals are sent and received between constituent parts such as the light emitting part 111 included in the tester 11; and the communication interface 104 is used to send and receive data with an external device (in this case, the high-level system 12).

FIG. 4 is a diagram showing the functional configuration of the control unit 118 . That is, the control unit 118 having the constituent parts shown in FIG. 4 is realized by the computer 10 performing processing according to the program for the control unit 118 . Functional components included in the control unit 118 will be described below.

The memory means 1180 is the memory of various materials. The materials memorized by the memory means 1180 include the following. (1) Options for air flow change step values, and a table showing the air flow change step values selected and set from the options (hereinafter referred to as "air flow change step value table"). (2) A table that temporarily stores the measured value of the flow meter 115 together with time information indicating the time at which the measured value was measured (hereinafter referred to as "flow rate temporary memory table"). (3) Among the measured values memorized in the temporary flow memory table, the measured value when the rate of change has reached the set air flow change step value, together with the time information indicating the time point when the measured value was measured Memorized table (hereinafter referred to as "flow recording table"). (4) The limit value used to determine the presence or absence of flow abnormalities. (5) The limit value used to determine the presence or absence of smoke.

Fig. 5 is a diagram illustrating an example of the structure of an air flow change step value table. The data of the airflow change step value table illustrated in Figure 5 shows that among the options of the so-called three airflow change step values of 10%, 20%, and 30%, the airflow change step value of 20% is now selected.

Fig. 6 is a diagram illustrating an example of the configuration of a flow rate temporary memory table. The flow rate temporary memory table has: a "time" column, which stores time information indicating the time after the measured value of the flow rate is measured; and a "flow rate" column, which stores the measured value of the flow rate measured at that time. In the flow temporary memory table, only two records are stored.

The data in the first line of the flow temporary memory table is the data that was added to the flow record table last. Also, the data in the second row of the flow rate temporary memory table is data representing the measured value of the flow rate measured by the flow meter 115 last and the time point after the measured value was measured. Hereinafter, the measured value stored in the "Flow" column of the first row of the temporary flow memory table is referred to as f(1), and the measured value stored in the "Flow" column of the second row of the temporary flow memory table is referred to as is f(2).

In this embodiment, the rate of change (%) between the set air flow change step value and the compared flow rate is represented by R in the following mathematical formula 1. R=|f(2)-f(1)|/f(1)×100 …(Formula 1) Furthermore, |X| represents the absolute value of X.

When the rate of change R reaches the set airflow change step value, the data in the second row of the flow temporary memory table will be added to the bottom row of the flow record table, and the data in the first row of the flow temporary memory table will be deleted. And the data in the second line will become the new data in the first line. After that, the latest measured value of the flowmeter 115 and the data representing the time after the measurement are sequentially rewritten on the second row.

Fig. 7 is a diagram illustrating an example of a configuration of a flow log table. The flow record table has: a "time" column that stores time information representing the time after the measured value of the flow is measured; and a "flow" column that stores the measured value of the flow measured at that time. In the flow recording table, there are stored in sequence: the measured value of the flow when the rate of change R of the air flow measured by the flow meter 115 has reached the set airflow change step value, and the measured value indicating that the measured value is measured. Data at a point in time.

Referring to FIG. 4 , the description of the functional configuration of the control unit 118 will be continued. The light-emitting instruction means 1181 instructs the light-emitting unit 111 to emit light. The light intensity signal acquisition means 1182 acquires a light intensity signal indicating the intensity of light received by the light receiving unit 112 . The light intensity signal acquired by the light intensity signal acquisition means 1182 is used by the smoke determination means 1186 .

The flow signal obtaining means 1183 obtains a flow signal indicating the measured value of the flow meter 115 . The measured value indicated by the flow signal acquired by the flow signal acquisition means 1183 is temporarily stored in the flow temporary memory table of the memory means 1180 together with the acquisition time point.

The record generating means 1184 generates record data representing the measured value when the rate of change of the measured value of the flowmeter 115 reaches the limit value. Specifically, the record generating means 1184 is based on the two measured values (f(1) and f(2)) stored in the temporary flow memory table of the memory means 1180, and calculates the rate of change according to the above-mentioned mathematical formula 1 R, and determine whether the calculated rate of change R reaches the airflow change step value selected in the airflow change step value table, and if the rate of change R reaches the selected airflow change step value, generate the first flow rate temporary memory table The copy of the second line is used as a new record data, and the record data is added to the bottom line of the flow record table. Also, the record generation means 1184 deletes the data in the first row of the temporary flow memory table when adding new record data to the flow record table as described above, and uses the data in the second row as the new first row information.

The flow abnormality judging means 1185 is to judge whether the measured value stored in the "flow" column of the second line of the temporary flow memory table reaches the limit value stored in the memory means 1180 for judging the flow abnormality. When the limit value for judging the traffic abnormality is reached, a traffic abnormality notification data for notifying the traffic abnormality is generated. The traffic abnormal notification data generated by the traffic abnormal judging means 1185 is sent to the high-level system 12 through the communication means 1189 .

The smoke judging means 1186 is to judge whether the light intensity indicated by the light intensity signal acquired by the light intensity signal acquiring means 1182 from the light emitting part 112 reaches the limit value memorized in the memory means 1180 for judging the presence or absence of smoke. When the intensity reaches a threshold value for judging the presence or absence of smoke, smoke generation notification data for notifying smoke generation is generated. The smoke occurrence notification data generated by the smoke judging means 1186 is sent to the high-level system 12 through the communication means 1189 .

The limit value change means 1187 is to change the set air flow change step value. Specifically, the limit value change means 1187 receives the operation signal output from the button 116 in response to the user's operation, and changes the record in the air flow change step value table of the memory means 1180 according to the received operation signal. , and the records with "○" are stored in the "Selection" column. For example, when the user presses and holds the button 116 every time, the "selection" column of the airflow change step value table stores the record with "○", which will be like the first record, the second record, the third record, the first record, ... cyclically change sequentially.

The light-emitting indicating means 1188 is to store the record with "○" in the "choice" column of the airflow change step value table. The light emitting unit 117 is instructed to emit light in a state corresponding to the set air flow change step value). An example of how the light emitting unit 117 emits light according to the light emitting instruction means 1188 is as described above.

The communication means 1189 (an example of the sending means and the receiving means) transmits and receives various data to and from the high-level system 12 . Specifically, as already mentioned, the communication means 1189 sends the traffic abnormality notification data to the high-level system 12 when the traffic abnormality notification data is generated by the traffic abnormality determination means 1185 . Also, as already mentioned, the communication means 1189 transmits the smoke occurrence notification data to the high-level system 12 when the smoke occurrence notification data is generated by the smoke determination means 1186 .

Also, for example, the communication means 1189 receives a transmission request of the flow record table from the high-order system 12, and sends a copy of the flow record table to the high-order system 12 in response to the transmission request. The high-level system 12, or the user of the high-level system 12, is based on the data stored in the flow record table received by the high-level system 12 from the smoke detection sensor 11 to analyze, for example, the change of the air flow rate with time, thereby being able to When the air flow rate has become out of the appropriate range, the cause is estimated, or the period before the air flow rate becomes out of the appropriate range is estimated to be out of the appropriate range.

The timing means 1190 continuously measures the current time, and generates time information indicating the current time after the measurement. The time information generated by the timing means 1190 is, for example, used as the time information stored in the "time" column of the flow temporary memory table.

According to the above-mentioned smoke detection sensing system 1, the user observes the record data stored in the flow record table and judges that it is wasteful to add record data to the flow record table at a higher frequency. By operating the button 116, the set airflow change step value can be increased. As a result, the so-called lack of useless record data stored in the flow record table can be alleviated, and the memory capacity of the memory means 1180 can be efficiently used.

Also, according to the above-mentioned smoke detection sensing system 1, the user observes the recorded data stored in the flow record table, and judges that the frequency of adding recorded data to the flow record table is too low, and can borrow By operating the button 116, the set airflow change step value is reduced. As a result, thereafter, the recorded data can be stored in the flow record table at an appropriate frequency, and the user can easily perform the estimation of the cause of the above-mentioned abnormal flow rate based on the recorded data.

[variation example] The above-mentioned embodiment is a specific example of the present invention, and various changes can be made within the scope of the technical idea of the present invention. The following are examples showing such changes. In addition, two or more modification examples shown below may be combined appropriately.

(1) In the above-mentioned embodiment, although the operation accepting means for accepting the user's operation on the smoke detector 11 is assumed to be the button 116, the mode of the operation accepting means included in the smoke detector 11 is Not limited to buttons. For example, physical operating elements such as sliders or switches, which are different from buttons, can also be used as the operation acceptance means of the smoke detector 11 . In addition, a touch screen can also be used as the means for accepting the operation of the smoke detector 11 . In this case, the operation accepting means displays a virtual operating element on the screen, and accepts a touch operation performed by the user on the virtual operating element.

(2) In the above-mentioned embodiment, the limit value changing means 1187 changes the set airflow change step value in response to the user's operation received by the operation accepting means exemplified by the button 116 . Instead, or in addition, the limit value changing means 1187 can also change the set airflow change step value in response to the data received by the communication means 1189 (an example of a receiving means) from the high-level system 12 (an example of an external device).

For example, when the user performs a predetermined operation on the high-level system 12, the high-level system 12 will send a request to the smoke detector 11 for the airflow change step value table, and the smoke detector 11 will respond to the sending request. A copy of the airflow variation step value table is sent to the higher order system 12 .

The high-level system 12 is to display the airflow change step value table received from the smoke detector 11 . When the user changes the airflow change step value selected in the displayed airflow change step value table to the high-level system 12, the high-level system 12 will generate the "selection" column of the record of the changed airflow change step value The airflow change step value table of "○" has been stored, and the airflow change step value table is sent to the smoke detector 11 .

The smoke detector 11 uses the airflow change step value table received from the high-level system 12 to rewrite the airflow change step value table stored in the memory means 1180 . In this way, the airflow change step value selected by the user after operating the high-level system 12 will be reset to the smoke detector 11 .

In the case of this modification, the user does not need to directly operate the smoke detector 11 , but can change the airflow change step value used in the smoke detector 11 .

(3) In the above-mentioned embodiment, the limit value changing means 1187 is to change the set air flow change step value in response to the operation performed by the user. Instead, the limit value changing means 1187 may change the set air flow changing step value based on the measured value of the flow meter 115 (an example of the flow measuring means).

In this variation example, instead of the airflow change step value table having the configuration shown in FIG. 5 , the memory means 1180 stores the airflow change step value table configured as illustrated in FIG. 8 . A "flow range" column is added to each record of the airflow change step value table in this modification.

For example, the limit value change means 1187 is the measured value stored in the second row of the "flow" column of the specific flow temporary memory table, that is, the air flow measured by the flow meter 115 at last, and enters the "flow rate" of the airflow change step value table. The flow rate change step value table is updated so that "○" is stored in the "selection" column of the record corresponding to the specified range within the range shown in the column of the flow rate range.

According to this change example, for example, if the air flow rate is lower and the flow rate is lower, even if the change of the flow rate is small, the value of the rate of change R of the flow rate is still larger, and it is stored in the column of "air flow change step value" in advance. The "Flow Range" column of the record with a smaller value stores the range of high flow, and the "Flow Range" column of the record with a larger value stores the range of low flow in the "Airflow Change Step Value" column, thereby In response to the current flow rate, it can automatically select the appropriate airflow change step value for use without relying on manual work. Therefore, the time for the user to select an appropriate airflow change step value can be saved.

In this modification example, instead of the airflow change step value table, the relational expression representing the corresponding relationship between the flow rate range and the airflow change step value can be memorized in the memory means 1180 in advance, and the limit value change means 1187, according to the relational expression Calculate the air flow change step value corresponding to the current flow rate, and set the calculated air flow change step value.

(4) In the above-mentioned embodiment, although the selectable airflow change step values are assumed to be discrete values such as 10%, 20%, and 30%, the number of selectable airflow change step values can also be increased, and can Sets the airflow change step value essentially selected from continuous values.

(5) In the above-mentioned embodiment, the record data of the air flow generated in the smoke detector 11 is memorized in the flow record table in the smoke detector 11 . Instead, or in addition, the recorded data can also be sent from the smoke detector 11 to an external device (eg, the high-level system 12 ), and stored in the external device.

(6) In the above-mentioned embodiment, although the hardware system of the control unit 118 is assumed to be a computer, the control unit 118, for example, can also be configured as an ASIC (Application Specific Integrated Circuit; FPGA (Field Field) Programmable Gate Array; field programmable gate array) and other dedicated devices for integrated circuits.

1: Smoke detection sensing system 10: computer 11: Smoke detector 12: Advanced system 101: Processor 102: memory 103: Input and output interface 104: Communication interface 110: shell 111: Luminous department 112: Light receiving part 113: fan 114: filter 115: flow meter 116: button 117: Luminous department 118: Control unit 1101: wall 1102, 1103: pipe 1180: memory means 1181, 1188: Luminous indicating means 1182: Light intensity signal acquisition means 1183: Flow signal acquisition means 1184: record generation means 1185: Judgment method of traffic abnormality 1186: Smoke Judgment Means 1187: Limit value change means 1189: means of communication 1190: Timing means P: suction port Q: Exhaust port S: Sensing area

[ Fig. 1 ] is a diagram showing the configuration of a smoke detection and sensing system according to an embodiment. [ Fig. 2 ] is a diagram schematically showing the configuration of a smoke detector according to an embodiment. [FIG. 3] It is a figure which shows the structure of the computer (computer) which employ|adopted the hardware (hardware) of the control unit (control unit) which is one embodiment. [ Fig. 4 ] is a diagram showing a functional configuration of a control unit according to an embodiment. [ Fig. 5 ] is a diagram illustrating the configuration of an air flow change step value table (table) according to an embodiment. [ Fig. 6 ] is a diagram illustrating the configuration of a flow rate temporary memory table according to an embodiment. [FIG. 7] It is a figure which exemplifies the structure of the flow rate recording table of one embodiment. [FIG. 8] It is a figure which exemplifies the structure of the airflow change step value table of a modification.

12: Advanced system

111: Luminous department

112: Light receiving part

115: flow meter

116: button

117: Luminous department

118: Control unit

1180: memory means

1181, 1188: Luminous indicating means

1182: Light intensity signal acquisition means

1183: Flow signal acquisition means

1184: record generation means

1185: Judgment method of traffic abnormality

1186: Smoke Judgment Means

1187: Limit value change means

1189: means of communication

1190: Timing means

Claims (5)

A smoke detection sensor is a smoke detection sensor that senses the occurrence of smoke in the aforementioned external space by sensing particles contained in the air flowing into the sensing area from the external space, and is characterized in that it has: Flow measuring means, which measure the flow of air; and record generation means, which is to generate record data indicating the measured value when the rate of change of the measured value of the aforementioned flow measurement means has reached a threshold value; and The limit value changing means is to change the aforementioned limit value. The smoke detector according to claim 1, wherein: an operation accepting means for accepting user's operation; The aforementioned limit value changing means is to change the aforementioned threshold value in response to the operation received by the aforementioned operation accepting means. The smoke detector as described in claim 1, wherein, it is provided with: receiving means for receiving data from an external device; The aforementioned limit value changing means is to change the aforementioned threshold value in response to the data received by the aforementioned receiving means. The smoke detector according to claim 1, wherein the threshold value changing means is to change the threshold value according to the measurement value of the flow measuring means. The smoke detector according to claim 4, wherein the limit value changing means is that the smaller the measured value of the flow measuring means is, the more the limit value is increased.

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