Smoke sensor, and fire alarm facility

Abstract

To enable obtaining a smoke sensor that can prevent erroneous sensing of smoke.SOLUTION: A smoke sensor (100) comprises: a smoke sensing part (50) for sensing smoke generated in a monitoring area to output a smoke sensing level indicating concentration of the sensed smoke; and a state monitoring part (20) for monitoring a state of an inner face of a flow channel (41) for allowing air in the monitoring area to pass through the smoke sensing part (50), or an object face (31) as a face of an interior of the smoke sensing part (50). The state monitoring part (20) has: a monitoring light-emitting part (21) for emitting light toward the object face (31); and a monitoring light-receiving part (22) for receiving reflected light of light emitted from the monitoring light-emitting part (21), from the object face (31) to output a light-receiving level indicating intensity of the received light as a monitoring light level.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a smoke detector and a fire alarm system that prevent false detection of smoke. [Background technology]

[0002] A smoke detector determines whether or not a fire has occurred within a monitored area by detecting the amount of light scattered by smoke from a light-emitting element provided inside the detector.

[0003] Furthermore, even if steam enters the smoke detector, the light from the light-emitting element is scattered, so the smoke detector may mistakenly detect the inflow of smoke and set off an alarm, even if steam is actually entering the detector.

[0004] Smoke detectors that prevent such false detection include the following (see, for example, Patent Document 1). The smoke detector in Patent Document 1 is equipped with a Peltier element in a smoke flow path that allows smoke to flow into the smoke detector. The smoke detector controls the Peltier element to the cooling side, causing the flowing steam to condense or freeze in the smoke flow path. This prevents the steam from reaching the smoke detector, preventing false detection. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-154324 Summary of the Invention [Problem to be solved by the invention]

[0006] The smoke detector of Patent Document 1 can also prevent false detection of smoke, but requires a considerable amount of electrical energy to cool the steam in the air to a level that causes it to condense.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a smoke detector and fire alarm system that can reduce electrical energy consumption while preventing false detection of smoke. [Means for solving the problem]

[0008] The smoke detector of the present disclosure comprises a smoke detection unit that detects smoke generated in a monitored area and outputs a smoke detection level indicating the concentration of the detected smoke, and a status monitoring unit that monitors the condition of a target surface, which is the inner surface of a flow path that passes air in the monitored area to the smoke detection unit or the internal surface of the smoke detection unit.The status monitoring unit has a monitoring light-emitting unit that emits light toward the target surface, and a monitoring light-receiving unit that receives reflected light emitted from the monitoring light-emitting unit from the target surface and outputs a light-receiving level indicating the intensity of the received light as a monitoring light level. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to obtain a smoke detector and a fire alarm system that can reduce electrical energy consumption and prevent false detection of smoke. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing the appearance of a smoke detector according to a first embodiment of the present disclosure. [Figure 2] 2 is a schematic diagram illustrating a part of the internal structure of the smoke detector shown in FIG. 1. FIG. [Figure 3] 3 is a schematic diagram showing an example of a structure in which the position of a state monitoring unit is changed with respect to the internal structure shown in FIG. 2. FIG. [Figure 4] FIG. 2 is a block diagram illustrating the configuration of the smoke detector shown in FIG. [Figure 5] 2 is a diagram illustrating an example of a smoke detection level and a monitoring light level when smoke flows into the smoke detector shown in FIG. 1. FIG. [Figure 6] 3 is a diagram illustrating an example of the smoke detection level and the monitoring light level when steam flows into the smoke detector shown in FIG. 1. FIG. [Figure 7]2 is a diagram illustrating an example of a monitoring light level when dust is added as a simulation in the smoke detector shown in FIG. 1. FIG. [Figure 8] 2 is a diagram illustrating an example of the smoke detection level and the monitor light level when hot and humid air is introduced into the smoke detector shown in FIG. 1. FIG. [Figure 9] 5 is a flowchart showing an example of control by the control unit shown in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, preferred embodiments of the smoke detector of the present disclosure will be described with reference to the drawings. The smoke detector according to the present disclosure is provided with a status monitoring unit that monitors the interior surface of the smoke detector in addition to a conventional smoke detection unit. The smoke detector according to the present disclosure also has a technical feature in that it is capable of determining whether what is detected by the smoke detection unit is smoke or another substance such as steam, based on the monitoring results of the status monitoring unit.

[0012] Embodiment 1 FIG. 1 is a perspective view showing an external appearance of a smoke detector according to a first embodiment of the present disclosure. In FIG. 1, the smoke detector 100 is a P-type detector, and a housing 10 is formed by a base 11 and a cover 12 .

[0013] The base 11 has an abutment surface 13. The smoke detector 100 is attached to a wall, ceiling, or other installation surface within a monitoring area by fixing the abutment surface 13 in contact with the wall, ceiling, or other installation surface.

[0014] The cover 12 has a vent 14 that connects the interior space of the housing 10 with the outside, and when smoke occurs in the monitored area, the smoke flows into the interior of the housing 10 through the vent 14.

[0015] Fig. 2 is a schematic diagram illustrating a part of the internal structure of the smoke detector 100 shown in Fig. 1. In Fig. 2, the smoke detector 100 includes a smoke detection unit 50 and a status monitoring unit 20.

[0016] The smoke detector 50 is a unit for detecting smoke, and includes a dark box 42, a smoke detector light emitter 51, and a smoke detector light receiver 52.

[0017] The dark box 42 is a part that forms a space that blocks light from outside. The smoke detection light-emitting unit 51 is a light-emitting body provided in the dark box 42, and the smoke detection light-receiving unit 52 is a light-receiving element corresponding to the smoke detection light-emitting unit 51.

[0018] The smoke detection light receiving unit 52 is provided in the dark box 42 and is installed in a position where it cannot be directly reached by light from the smoke detection light emitting unit 51. Therefore, the smoke detection light receiving unit 52 does not receive light from the smoke detection light emitting unit 51 during normal times when no smoke is being generated.

[0019] On the other hand, when smoke flows into the dark box 42 from the monitored area through the vent 14, the light from the smoke detection light-emitting unit 51 hits the smoke particles and is scattered, and some of the light reaches the smoke detection light-receiving unit 52. The smoke detection unit 50 detects whether a fire has occurred in the monitored area based on the amount of light received by the smoke detection light-receiving unit 52. The amount of light received by the smoke detection light-receiving unit 52 is referred to here as the smoke detection level, and is output as an AD value.

[0020] The status monitoring unit 20 includes a monitoring light-emitting unit 21 and a monitoring light-receiving unit 22, and monitors a target surface 31. In Fig. 2, the status monitoring unit 20 monitors the inner surface of a flow path 41 that passes air in the monitoring area to the smoke detection unit 50, as the target surface 31.

[0021] The monitoring light-emitting unit 21 is a light-emitting body that emits light toward the target surface 31 through the window material 23. There are no particular restrictions on the wavelength of the light from the monitoring light-emitting unit 21, but in the first embodiment, infrared light is used, which requires a low driving voltage.

[0022] The monitoring light receiving unit 22 receives the reflected light of the light emitted from the monitoring light emitter 21 from the target surface 31. The monitoring light receiving unit 22 then outputs a light receiving level indicating the intensity of the received light. Here, this light receiving level is referred to as a monitoring light level, and is output as an AD value.

[0023] FIG. 3 is a schematic diagram showing an example of the internal structure shown in FIG. 2 in which the position of the state monitoring unit 20 is changed.

[0024] The state monitoring unit 20 shown in FIG. 3 monitors the inner surface of the dark box 42 constituting the smoke detection unit 50 as the target surface 31 .

[0025] Because the amount of light emitted by the monitoring light-emitting unit 21 is less than the amount of light emitted by the smoke detection light-emitting unit 51, it does not affect smoke detection even when placed inside the dark box 42. Even if the amount of light is increased, by alternating the emission timing so that the light emitted by the monitoring light-emitting unit 21 and the light emitted by the smoke detection light-emitting unit 51 do not interfere with each other, the status monitoring unit 20 can monitor the target surface 31 without affecting smoke detection.

[0026] FIG. 4 is a block diagram illustrating the configuration of the smoke sensor 100 shown in FIG.

[0027] As shown in FIG. 4, the smoke detector 100 includes a control unit 60, an alarm unit 70, and a humidity measurement unit 80 in addition to the smoke detection unit 50 and the status monitoring unit 20 shown in FIGS.

[0028] The alarm unit 70 transmits a fire signal from the control unit 60, which will be described later, to the receiver.

[0029] The humidity measuring unit 80 is a hygrometer that measures the humidity in the monitoring area.

[0030] The control unit 60 determines whether or not there is a fire based on the smoke detection level output from the smoke detection unit 50 and the monitoring light level output from the monitoring light receiving unit 22 of the status monitoring unit 20, and sends a fire signal to the receiver from the alarm sending unit 70. The receiver that receives the fire signal sends a ringing instruction to an audio device such as a district bell based on the area monitored by the smoke detector 100.

[0031] The control contents of the control unit 60 will be specifically described in detail below.

[0032] FIG. 5 is a diagram illustrating an example of the smoke detection level and the monitor light level when smoke enters the smoke detector 100 shown in FIG.

[0033] 5, smoke detection unit 50 outputs a smoke detection level signal value of less than 100 until it detects smoke. In contrast, after smoke detection unit 50 detects smoke 20 seconds after the reference time, the signal value rises significantly to about 1000. Then, after about 10 seconds, the smoke detection level falls to about 600, and then gradually decreases.

[0034] Meanwhile, the monitoring light level of the status monitoring unit 20 during this time remains unchanged at a value of about 40 to 50.

[0035] One of the reasons why the monitoring light level does not increase when smoke enters the smoke detector 100 is that the light from the monitoring light-emitting unit 21 is partially blocked and diffused by the smoke passing through the flow path 41 shown in Figure 2. In addition, when the wavelength of the light and the particle diameter of the smoke are approximately the same, the intensity of the scattered light is higher in the forward direction of the light irradiation than in the backward direction. Therefore, the light from the monitoring light-emitting unit 21 is scattered upward in Figure 2, making it difficult for the light to reach the monitoring light-receiving unit 22 directly, which is also thought to be one of the reasons why the monitoring light level does not increase.

[0036] Due to these factors, when smoke enters the smoke detector 100, the amount of light received by the monitoring light receiving section 22 does not change, or at least does not increase significantly.

[0037] FIG. 6 is a diagram illustrating the smoke detection level and the monitoring light level in the smoke detector 100 shown in FIG. 1 when steam flows in. In FIG.

[0038] 6, the smoke detector 50 detects steam 10 seconds and 65 seconds after the reference time. The monitor light level of the status monitor 20 also rises to about 200 in conjunction with this.

[0039] When steam flows into the smoke detector 100, the monitoring light level increases because, in addition to the light reflected from the target surface 31, the light hits droplets of condensation that form on the wall surface as the steam passes, causing diffuse reflection, and the reflected light from these droplets reaches the monitoring light receiving unit 22.

[0040] As can be seen from the graph in Figure 5, when smoke flows into the smoke detector 100, the smoke detection level of the smoke detector 50 increases, but the monitoring light level of the status monitoring unit 20 does not increase. On the other hand, as can be seen from the graph in Figure 6, when steam flows into the smoke detector 100, the smoke detection level of the smoke detector 50 increases, and the monitoring light level of the status monitoring unit 20 also increases.

[0041] The control unit 60 can determine whether the smoke detection unit 50 has detected smoke or steam by detecting the difference in the waveforms of the monitoring light levels shown in Figures 5 and 6.

[0042] In this way, it is possible to prevent erroneous detection due to mistaking steam for smoke by using the status monitoring unit 20. On the other hand, because dust such as dirt and grime also scatters light, the cause of erroneous detection is not limited to steam, and if a large amount of dust is generated, it may also be mistaken for smoke.

[0043] When the smoke detector 100 is used for a long period of time, dust accumulates on the inner surface of the flow path 41. If such accumulated dust is detached from the flow path 41 due to vibration or the like and flows into the dark box 42, the smoke detector 50 may mistake the dust for smoke and set off an alarm.

[0044] In addition to dust accumulation, high temperature and humidity conditions must also be considered as a factor in false detection of smoke. In hot and humid weather, such as summer, the inside of smoke detector 100 is also in a high temperature and humidity state. If smoke detector 100 is suddenly cooled by an air conditioner or the like at this time, the inside of smoke detector 100 will become cloudy and foggy.

[0045] When mist is generated inside the smoke detector 100 in this way, as in the case of steam, the smoke detector 50 may mistakenly recognize the mist as smoke and set off an alarm.

[0046] That is, it is necessary to predict in advance the state of dust accumulation and the state of high temperature and humidity, and by predicting these conditions, it is possible to avoid false detection by the smoke detection unit 50. Below, a method for predicting these causes of false detection in advance using the state monitoring unit 20 will be described.

[0047] FIG. 7 is a diagram illustrating the monitoring light level when dust is added as a simulation in the smoke sensor 100 shown in FIG.

[0048] In the graph of Fig. 7, dust is added to the target surface 31 about 90 to 100 seconds after the reference time, and then dust is added again to the target surface 31. In other words, dust is added to the target surface 31 in two separate steps. Then, in the graph of Fig. 7, all of the added dust is removed from the target surface 31 about 180 seconds after the reference time.

[0049] As shown in the graph in Fig. 7, when dust adheres, the monitor light level from the state monitoring unit 20 becomes higher than the initial value. Also, the monitor light level increases when dust is added twice rather than once. Therefore, it can be seen from the graph in Fig. 7 that the more dust accumulates, the higher the monitor light level becomes.

[0050] In addition, it can be seen from the graph of FIG. 7 that removing the dust causes the monitoring light level to return to its initial value.

[0051] For this reason, when the monitoring light level increases by a specified value from the initial value, the smoke detector 100 can issue a warning notification that there is a risk of false detection due to dust.

[0052] FIG. 8 is a diagram illustrating the smoke detection level and the monitor light level in smoke detector 100 shown in FIG. 1 when hot and humid air is introduced.

[0053] In Figure 8, approximately 10 seconds after the reference time, hot and humid air is introduced into smoke detector 100. Then, 50 to 60 seconds after the reference time, the inside of smoke detector 100 is ventilated with normal room air.

[0054] In the case of hot and humid air, neither the smoke detection level nor the monitoring light level increases significantly like the steam level shown in Figure 6. However, Figure 8 shows that the monitoring light level increases from its initial value.

[0055] Therefore, when the monitor light level increases by a specified value from the initial value, the smoke detector 100 can issue a warning notification that there is a risk of false detection due to high temperature and humidity conditions.

[0056] By using this method, the smoke detector 100 can predict the occurrence of a false detection by the smoke detection unit 50. Note that the measurement value by the humidity measurement unit 80 can be used to determine whether the increase in the monitoring light level is due to dust accumulation or a high temperature and humidity condition.

[0057] That is, if the measurement value by the humidity measuring unit 80 reaches the specified humidity threshold, the smoke detector 100 determines that a high temperature and humidity state exists. On the other hand, if the measurement value by the humidity measuring unit 80 does not reach the specified humidity threshold, the smoke detector 100 determines that dust has accumulated.

[0058] Fig. 9 is a flowchart showing an example of control by the control unit 60 shown in Fig. 4. The process of Fig. 9 is repeatedly executed.

[0059] In step S101, the control unit 60 determines whether the smoke detection level of the smoke detection unit 50 has reached a preset smoke detection threshold. Here, the smoke detection threshold is a threshold for determining whether an alarm should be issued. If the smoke detection level has reached the smoke detection threshold, the process proceeds to step S102 to determine whether the fire is caused by smoke or by a false detection factor. On the other hand, if the smoke detection level has not reached the smoke detection threshold, the control unit 60 determines that no fire has occurred in the monitored area, and the process proceeds to step S201.

[0060] In step S102, the control unit 60 determines whether the monitor light level detected by the status monitoring unit 20 has reached a preset monitor light threshold. Here, the monitor light threshold is a threshold for distinguishing between what is detected as smoke and what is a cause of false detection. If the monitor light level has reached the monitor light threshold, the control unit 60 determines that the smoke detection unit 50 has detected a cause of false detection and not smoke. Then, in step S104, the control unit 60 prevents the alarm issuing unit 70 from issuing an alarm, and ends the processing of FIG. 9. As a result, an alarm due to false detection will no longer be issued.

[0061] On the other hand, if the monitor light level does not reach the monitor light threshold in step S102, the control unit 60 determines that the smoke detection unit 50 has detected smoke. Then, in step S103, the control unit 60 causes the alarm unit 70 to issue an alarm, and ends the processing of Fig. 9. Therefore, if smoke is detected, an alarm is issued correctly.

[0062] Next, step S201 will be described. If the smoke detection level has not reached the smoke detection threshold, the control unit 60 determines in step S201 whether the monitor light level monitored by the status monitoring unit 20 has increased by a preset specified value from the initial value. If the monitor light level has not increased by the specified value from the initial value, the control unit 60 ends the processing of Fig. 9. In this case, since no smoke is generated and no foreseeable causes of erroneous detection have occurred, the control unit 60 ends the processing without issuing any notification.

[0063] On the other hand, if the monitoring light level has increased by the specified value from the initial value in step S201, the control unit 60 determines in step S202 whether the measurement value of the humidity measurement unit 80 has reached a preset humidity threshold. If the measurement value of the humidity measurement unit 80 has reached the humidity threshold, the control unit 60 issues a warning notification that a high temperature and high humidity state has occurred via the alarm issuing unit 70 in step S204. After step S204, the control unit 60 ends the processing of FIG. 9.

[0064] On the other hand, if the measurement value of humidity measurement unit 80 does not reach the humidity threshold value, in step S203, control unit 60 issues a warning notification that dust is accumulating inside smoke detector 100 via alarm unit 70. After step S203, control unit 60 ends the processing of FIG. 9.

[0065] In a high temperature and humidity situation, the condition will be resolved in a relatively short time and return to normal. Therefore, when it is determined that the temperature and humidity is high, instead of issuing a warning, it may be possible to wait for a time longer than the normal determination processing interval and then perform the determination processing of step S101.

[0066] Furthermore, if it is determined that the temperature and humidity are high, steps S201 to S204 may be repeated until the high temperature and humidity situation is resolved.

[0067] Furthermore, if it is determined that the temperature and humidity are high, the hot and humid air remaining inside the smoke detector 100 may be exhausted using a fan or the like.

[0068] Furthermore, if it is determined that dust has accumulated or that the environment is hot and humid, a signal may be sent to the receiver. In this case, the receiver will not issue an instruction to ring a district bell or other audio equipment, but will instead display the district where the dust has accumulated and the situation.

[0069] The smoke detector 100 has the following features and can achieve the following effects.

[0070] The control unit 60 determines whether the smoke detection level, which increases due to scattered light caused by smoke particles, has reached the smoke detection threshold. At this time, the influence of steam or dust may cause the smoke detection level to reach the smoke detection threshold, resulting in a false detection.

[0071] Therefore, the control unit 60 acquires the reflected light from the target surface 31 as a monitor light level and monitors the situation where the reflected light increases due to steam or dust. The scattered light from smoke particles does not increase the reflected light from the target surface 31, and the occurrence of smoke will not cause the monitor light level to reach the monitor light threshold.

[0072] Therefore, by monitoring the transition states of both the smoke detection level and the monitor light level, the control unit 60 can suppress false detection and improve the accuracy of smoke detection.

[0073] More specifically, the smoke detector 100 comprises a smoke detection unit 50 that detects smoke generated in the monitored area and outputs a smoke detection level indicating the concentration of the detected smoke, and a status monitoring unit 20 that monitors the status of the target surface 31, which is the inner surface of a flow path 41 that passes air in the monitored area to the smoke detection unit 50 or the internal surface of the smoke detection unit 50.

[0074] The status monitoring unit 20 also has a monitoring light emitting unit 21 that emits light toward the target surface 31, and a monitoring light receiving unit 22 that receives the reflected light of the light emitted from the monitoring light emitting unit 21 from the target surface 31 and outputs the received light level indicating the intensity of the received light as a monitoring light level.

[0075] Therefore, it is possible to obtain a smoke detector 100 that can prevent erroneous detection of smoke.

[0076] The smoke detector 100 also includes a control unit 60 that controls whether or not to issue a fire alarm based on the smoke detection level output from the smoke detector 50 and the monitoring light level output from the monitoring light receiver 22.

[0077] Therefore, it is possible to determine whether the smoke detection unit 50 has detected smoke or a substance other than smoke.

[0078] Furthermore, the control unit 60 performs control so as not to issue an alarm when the smoke detection level reaches the smoke detection threshold and the light reception level reaches the monitor light threshold.

[0079] Therefore, if a substance other than smoke is detected, an alarm can be prevented from being issued.

[0080] The control unit 60 further determines, based on the monitoring light level output from the monitoring light receiving unit 22, whether or not a factor causing the smoke detector 50 to erroneously detect smoke has occurred.

[0081] Furthermore, the control unit 60 determines whether or not a factor causing erroneous smoke detection has occurred based on whether or not the level of the monitoring light output from the monitoring light receiving unit 22 has increased from the initial value.

[0082] Therefore, it is possible to predict whether a situation in which a false detection may occur is present.

[0083] The smoke detector 100 further includes a humidity measuring unit 80. Based on the humidity measured by the humidity measuring unit 80, the control unit 60 determines whether the cause of the false smoke detection is dust accumulation on the target surface 31 or a high temperature and humidity state.

[0084] Therefore, the smoke sensor 100 can further identify the cause of the false smoke detection.

[0085] The smoke detector 100 is a P-type detector that automatically determines whether a fire has occurred using the built-in control unit 60. However, the first embodiment can also be applied to a fire alarm system that includes an R-type detector and a receiver.

[0086] In this case, the control unit of the R-type detector converts the status of the smoke detector 50, status monitor 20, and humidity meter 80 into signals, and sends the signals to the receiver from the alarm unit. The receiver that receives the signals determines whether there is a fire or not, determines the status of the detector, and issues an instruction to sound the audio equipment or displays the status on the receiver panel.

[0087] The smoke detector 100 and the R-type detector may be configured without the humidity measuring unit 80. In this case, it is not possible to distinguish between a state where dust has accumulated and a state where the temperature is high and the humidity is high, but it is possible to report a state where there is a risk of false detection.

[0088] Furthermore, the smoke detector 100 described above is a P-type detector that transmits a fire signal from the alarm unit 70 to a receiver, and the receiver that receives the fire signal commands the sounding of an audio device such as a district bell. However, the detector can also be applied to a residential fire alarm equipped with an audio unit. In this case, the alarm unit 70 issues a sounding command to the audio unit, and the audio unit sounds a sound or voice to indicate a fire. In this case, the audio unit may also sound an alarm to indicate conditions such as dust accumulation or high temperature and humidity. [Explanation of symbols]

[0089] 10 housing, 11 base, 12 cover, 13 contact surface, 14 ventilation hole, 20 status monitoring unit, 21 monitoring light-emitting unit, 22 monitoring light-receiving unit, 23 window material, 31 target surface, 41 flow path, 42 dark box, 50 smoke detection unit, 51 smoke detection light-emitting unit, 52 smoke detection light-receiving unit, 60 control unit, 70 alarm unit, 80 humidity measurement unit, 100 smoke detector.

Claims

1. a smoke detection unit that detects smoke generated in a monitoring area and outputs a smoke detection level indicating the concentration of the detected smoke; a status monitoring unit that monitors the status of a target surface, which is an inner surface of a flow path that passes air in the monitoring area to the smoke detector or an internal surface of the smoke detector; Equipped with The state monitoring unit a monitoring light emitting unit that emits light toward the target surface; a monitoring light receiving unit that receives reflected light of light emitted from the monitoring light emitting unit from the target surface and outputs a light receiving level indicating the intensity of the received light as a monitoring light level; A smoke detector having:

2. a control unit that controls whether to issue a fire alarm based on the smoke detection level output from the smoke detector and the monitoring light level output from the monitoring light receiving unit; 10. The smoke detector of claim 1.

3. The control unit controls so as not to issue the alarm when the smoke detection level reaches a smoke detection threshold and the light reception level reaches a monitoring light threshold.

3. The smoke detector of claim 2.

4. The control unit further determines whether or not a cause of erroneous smoke detection, which is a cause of erroneous smoke detection by the smoke detection unit, has occurred based on the monitoring light level output from the monitoring light receiving unit.

4. A smoke detector according to claim 2 or 3.

5. the control unit determines whether the cause of the false smoke detection has occurred based on whether the monitoring light level output from the monitoring light receiving unit has increased from an initial value.

5. The smoke detector of claim 4.

6. Further comprising a humidity measuring unit, The control unit determines whether the cause of the false smoke detection is dust accumulation on the target surface or a high temperature and humidity state based on the humidity measured by the humidity measuring unit.

6. The smoke detector of claim 5.

7. a smoke detection unit that detects smoke generated in a monitoring area and outputs a smoke detection level indicating the concentration of the detected smoke; a status monitoring unit that monitors the status of a target surface, which is an inner surface of a flow path that passes air in the monitoring area to the smoke detector or an internal surface of the smoke detector; Equipped with The state monitoring unit a monitoring light emitting unit that emits light toward the target surface; a monitoring light receiving unit that receives reflected light of light emitted from the monitoring light emitting unit from the target surface and outputs a light receiving level indicating the intensity of the received light as a monitoring light level; A smoke detector having: a receiver that controls whether or not to issue a fire alarm based on the smoke detection level output from the smoke detector and the monitoring light level output from the monitoring light receiving unit; Fire alarm equipment.

8. the receiver controls not to issue the alarm when the smoke detection level reaches a smoke detection threshold and the monitoring light level reaches a monitoring light threshold; The fire alarm system according to claim 7.

9. The receiver further determines whether or not a cause of erroneous smoke detection that may cause the smoke detector to erroneously detect smoke has occurred, based on the monitoring light level output from the monitoring light receiving unit. The fire alarm system according to claim 7 or 8.

10. The receiver determines whether the cause of the false smoke detection has occurred based on whether the monitoring light level output from the monitoring light receiving unit has increased from an initial value. The fire alarm system according to claim 9.

11. The smoke detector further includes a humidity measuring unit, The receiver determines whether the cause of the false smoke detection is dust accumulation on the target surface or a high temperature and humidity state based on the humidity measured by the humidity measuring unit. The fire alarm system according to claim 10.

Images