Photoelectric smoke detector

Abstract

To secure simultaneity of measurement to improve detection accuracy, to reduce the number of components to simplify a structure, and to improve reliability, for a smoke detection unit structure for receiving scattered light by a difference in scattering characteristics of light with different wavelength to identify a kind of smoke.SOLUTION: In a photoelectric smoke detector, in a smoke detection unit 18, a light emitting element 20 using a white light emitting diode simultaneously emits light with a first wavelength and a second wavelength toward a smoke detection space, and a first light emitting element 22 having sensitivity to the light with the first wavelength and a second light emitting element 24 having sensitivity to the light with the second wavelength are provided at positions with different intersection angles where the light emitted from the light emitting element is not directly received. A kind of smoke is identified to identify whether a matter flowing in the smoke detection space for performing fire determination is smoke or steam by a criterion according to the kind of smoke by comparing light receiving output of smoke scattered light by a small scattering angle by the light with the first wavelength received by the first light receiving element with light receiving output of smoke scattered light by a large scattering angle received by the second light receiving element 24.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a photoelectric smoke detector that emits light of two wavelengths with different scattering characteristics for a light receiving element to distinguish and detect the type of smoke caused by a fire. [Background technology]

[0002] Conventional photoelectric smoke detectors can give false fire alarms not only when they detect smoke from fires, but also when they detect cooking smoke or steam from the bathroom.

[0003] In order to prevent false fire alarms due to causes other than fire, a photoelectric smoke detector has been proposed that shines light of two wavelengths into the smoke detection space and determines the ratio of the light intensities of the different wavelengths of the light scattered by the smoke to determine the type of smoke, thereby increasing the accuracy of smoke identification and ensuring the prevention of false fire alarms (Patent Document 1).

[0004] In the photoelectric smoke detector of Patent Document 1, differences in scattering characteristics due to the type of smoke are created by varying the scattering angle relative to the light receiving element for two light-emitting elements that emit light of different wavelengths, and at the same time, differences in the wavelength of light emitted from the two light-emitting elements are created to create differences in scattering characteristics due to wavelength. The synergistic effect of these differences in scattering angle and wavelength creates a significant difference in the light intensity of the scattered light depending on the type of smoke, thereby increasing the accuracy of smoke identification, preventing false fire alarms caused by cooking steam or cigarette smoke, and further making it possible to reliably identify the type of burning material, such as black smoke fires and white smoke fires, for smoke caused by fires. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-325211 A [Patent Document 2] Japanese Patent Application Publication No. 6-109631 [Patent Document 3] Japanese Patent Application Publication No. 7-12724 [Patent Document 4] International Publication No. 2005 / 048208 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in such conventional photoelectric smoke detectors, the two light-emitting elements must be illuminated alternately, so if there is fluctuation in the smoke flowing into the smoke detection section, the smoke densities measured will differ over time, which reduces the simultaneity of the measurements and leads to a decrease in detection accuracy.

[0007] In addition, because there are two light-emitting elements, which are the components that determine the sensor's lifespan, there is a corresponding increase in the probability of failure, raising concerns about a shortened product lifespan.

[0008] The present invention aims to provide a photoelectric smoke detector with a smoke detection section structure that receives scattered light due to differences in the scattering characteristics of light of different wavelengths and identifies the type of smoke, which ensures simultaneous measurement to improve detection accuracy, while reducing the number of parts, simplifying the structure, and improving reliability. [Means for solving the problem]

[0009] (Photoelectric smoke detector 1) The present invention is a photoelectric smoke detector, a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space; a first light receiving element that is provided at a position where it does not directly receive light emitted from the light emitting element and that is sensitive to light of a first wavelength; a second light receiving element that is provided at a different position so as not to directly receive the light emitted from the light emitting element and that is sensitive to light of a second wavelength; Equipped with The type of smoke that has flowed into the smoke detection space or the type of fire that caused the smoke is identified by comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold, and the threshold is changed depending on the magnitude of the first light receiving output or the second light receiving output.

[0010] (Photoelectric smoke detector 2) The present invention is a photoelectric smoke detector, a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space; a first light receiving element that receives light of a first wavelength emitted from the light emitting element; a second light receiving element that receives light of a second wavelength emitted from the light emitting element; Equipped with The type of smoke that has flowed into the smoke detection space or the type of fire that caused the smoke is identified by comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold value, and the threshold value is increased as the first light receiving output or the second light receiving output increases.

[0011] (Photoelectric smoke detector 3) The present invention is a photoelectric smoke detector, a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space; a first light receiving element that receives light of a first wavelength emitted from the light emitting element; a second light receiving element that receives light of a second wavelength emitted from the light emitting element; Equipped with The type of smoke that has flowed into the smoke detection space or the type of fire that has caused the smoke is identified by comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a first threshold value, and the ratio of the first light receiving output and the second light receiving output with a second threshold value is compared to identify whether what has flowed into the smoke detection space is smoke or steam.

[0012] If the type of smoke is identified, information indicating the type of smoke, which is the identification result, is transmitted to the fire receiver.

[0013] If steam is identified, information indicating that the identification result is steam is transmitted to the fire receiver. Effect of the Invention

[0014] (Basic Effects) The present invention provides a photoelectric smoke detector comprising a light-emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space, a first light-receiving element that is disposed in a position that does not directly receive the light emitted from the light-emitting element and is sensitive to light of the first wavelength, and a second light-receiving element that is disposed in another position that does not directly receive the light emitted from the light-emitting element and is sensitive to light of the second wavelength. Therefore, light of the first wavelength and the second wavelength are irradiated from the light-emitting element into the smoke detection space, and the first light-receiving element and the second light-receiving element can simultaneously receive scattered light, so that there is no deviation in measurement timing due to the light of the first wavelength and the second wavelength, and the detector is not affected even if the smoke concentration flowing into the smoke detection space fluctuates in a short period of time, thereby improving the accuracy of identifying the type of smoke.

[0015] (Effect of changing threshold) By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold, the type of smoke that has flowed into the smoke detection space or the type of fire that caused the smoke is identified, and the threshold is changed according to the magnitude of the first light receiving output or the second light receiving output.Therefore, if the smoke concentration becomes extremely high, it is possible that the threshold will be exceeded due to the effects of secondary scattering, and the threshold can be changed to compensate for this, making it possible to determine the type of smoke with high accuracy.

[0016] (Effect of increasing threshold) By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold, the type of smoke that has flowed into the smoke detection space or the type of fire that caused the smoke is identified, and the threshold is increased as the first light receiving output or the second light receiving output increases.Therefore, if the smoke concentration becomes extremely high, it is possible that the threshold will be exceeded due to the effects of secondary scattering, and therefore the threshold can be changed to compensate for this, making it possible to determine the type of smoke with high accuracy.

[0017] (The effect of distinguishing between smoke and steam) By comparing the ratio between the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a first threshold value, the type of smoke that has flowed into the smoke detection space or the type of fire that caused the smoke can be identified, and by comparing the ratio between the first light receiving output and the second light receiving output with a second threshold value, it can be identified whether what has flowed into the smoke detection space is smoke or steam.If a non-fire factor such as steam is identified, a status signal including non-fire information indicating steam can be sent to the receiver, causing the receiver to output a caution alarm rather than a fire alarm.

[0018] (Effect of transmitting the identification result to the fire receiver) If the type of smoke is identified, information indicating the type of smoke, which is the identification result, is sent to the fire receiver, and if steam is identified, information indicating that the identification result is steam, so that the fire receiver can output an alarm according to the information. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a block diagram showing the circuit configuration of a photoelectric smoke detector according to the present invention. [Diagram 2] FIG. 1 is an explanatory diagram showing an embodiment of a smoke detector structure. [Diagram 3] An explanatory diagram showing the light receiving output and its ratio of the first and second light receiving elements detected by the smoke detector structure of FIG. 2 when a cotton wick and kerosene are burned. [Figure 4] FIG. 13 is an explanatory diagram showing a setting table for changing a ratio threshold value for identifying the type of smoke according to the light receiving output of the first light receiving element and the second light receiving element. [Diagram 5] FIG. 13 is an explanatory diagram showing a setting table of ratio thresholds for identifying types of smoke and non-fire factors according to the light receiving outputs of the first light receiving element and the second light receiving element. [Figure 6] 2. A flow chart showing an embodiment of fire detection control by the circuit block of FIG. 1 using the smoke detector structure of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [Circuit configuration of photoelectric smoke detector] Fig. 1 is a block diagram showing the circuit configuration of a photoelectric smoke detector according to the present invention. As shown in Fig. 1, a photoelectric smoke detector 10 of this embodiment is composed of a control unit 12 composed of a computer circuit equipped with a CPU, memory, and various input / output ports, a transmission unit 14 that transmits and receives signals to and from a fire receiver via transmission lines 11a and 11b connected to S and SC terminals, a power supply unit 15 that converts the power supply voltage supplied via the transmission lines 11a and 11b into a predetermined stabilized voltage and outputs it, a light emission drive unit 16, a smoke detection unit 18, and amplifier circuit units 26 and 28.

[0021] The smoke detector 18 is provided with a light emitting element 20 that simultaneously emits light including a first wavelength λ1 and a second wavelength λ2. The light of the first wavelength λ1 emitted from the light emitting element 20 has a central wavelength set to 600 nm or more, and the light of the second wavelength λ2 has a central wavelength set to 500 nm or less, and in this embodiment, the first wavelength λ1 is set to, for example, 700 nm, and the second wavelength λ2 is set to, for example, 450 nm.

[0022] In this embodiment, a white LED (white light emitting diode) is used as the light emitting element 20. The white LED is, for example, a combination of a blue LED and a phosphor, and the light of the blue LED passes through the phosphor to emit white light, and this emitted light color includes light with a first wavelength λ1=700 nm and light with a second wavelength λ2=450 nm, and the light of the first wavelength λ1 and the light of the second wavelength λ2 can be simultaneously irradiated into the smoke detection unit 18.

[0023] In addition, a two-color LED (two-color light-emitting diode) can also be used as the light-emitting element 20 of this embodiment. The two-color LED includes a first light-emitting chip that emits light with a first wavelength λ1=700 nm and a second light-emitting chip that emits light with a second wavelength λ2=450 nm, and by driving both of them simultaneously, the smoke detection unit 18 can be irradiated with light of the first wavelength λ1 and the second wavelength λ2 simultaneously.

[0024] The first light receiving element 22 uses a photodiode (PD) sensitive to the first wavelength λ1, and the second light receiving element 24 uses a photodiode (PD) sensitive to the second wavelength λ2.

[0025] In addition, the first light receiving element 22 and the second light receiving element 24 may be a wideband photodiode sensitive to the visible light wavelength band, with a filter layer that receives only the wavelength bands of the first wavelength λ1 and the second wavelength λ2 provided in a PD molding (transparent cover member), or a filter that transmits the wavelength bands of the first wavelength λ1 and the second wavelength λ2 may be disposed in front of the wideband photodiode.

[0026] The amplifier circuit section 26 amplifies the light receiving signal of the smoke scattered light of the first wavelength λ1 received by the first light receiving element 22, and provides a light receiving output A1 to the control section 12. In addition, the amplifier circuit section 28 amplifies the light receiving signal of the smoke scattered light received by the second light receiving element 24, and provides a light receiving output A2 to the control section 12.

[0027] [Embodiment of smoke detector] Fig. 2 is an explanatory diagram showing an embodiment of the structure of the smoke detection unit in Fig. 1. As shown in Fig. 2, a light emitting element 20, a first light receiving element 22 and a second light receiving element 24 are arranged in a smoke detection unit 18 into which smoke from the outside flows.

[0028] For example, a light-emitting element 20 using a white LED emits light including a first wavelength λ1 and a second wavelength λ2 in the direction of an optical axis 20a, and as described above, the light of the first wavelength λ1 is set to 700 nm, and the light of the second wavelength λ2 is set to 450 nm.

[0029] The first scattering angle θ1 formed by the intersection of the optical axis 20a of the light-emitting element 20 and the optical axis 22a of the first light-receiving element 22 is set in the range of 20° to 70°, and the optical axis 20a of the light-emitting element 20 and the optical axis 22a of the first light-receiving element 22 are arranged to intersect at a predetermined angle in the range of 110° to 160°.

[0030] In addition, the second scattering angle θ2 formed by the intersection of the optical axis 20a of the light-emitting element 20 and the optical axis 24a of the second light-receiving element 24 is set to the range of 110° to 150°, and the light-emitting element 20 and the optical axis 24a of the second light-receiving element 24 are arranged so that they intersect at a predetermined angle in the range of 30° to 70°.

[0031] In this embodiment, the first scattering angle θ1 is set to 30°, and therefore the optical axis 20a of the light-emitting element 20 and the optical axis 22a of the first light-receiving element 22 are arranged to intersect at a crossing angle of, for example, 150°, and the second scattering angle θ2 is set to 120°, and therefore the optical axis 20a of the light-emitting element 20 and the optical axis 24a of the second light-receiving element 24 are arranged to intersect at a crossing angle of, for example, 60°.

[0032] Since the first light receiving element 22 has sensitivity to light of the first wavelength λ1 = 700 nm emitted from the light emitting element 20, when the light emitting element 20 emits light of the first wavelength λ1, the scattered light at a scattering angle θ1 = 30° by the smoke that has flowed into the smoke detection unit 18 is received by the first light receiving element 22, and a received light output A1 is obtained. Here, the received light output A1 can be said to be a smoke concentration detection output detected by the first wavelength λ1 and the first scattering angle θ1.

[0033] Moreover, since the second light receiving element 24 has sensitivity to the light of the second wavelength λ2 = 450 nm emitted from the light emitting element 20, when the light emitting element 20 emits light of the second wavelength λ2 simultaneously with the light of the first wavelength λ1, the scattered light at the second scattering angle θ2 = 120° by the smoke that has flowed into the smoke detection unit 18 is received by the second light receiving element 24, and a received light output A2 is simultaneously obtained. Here, the received light output A2 can be said to be a smoke concentration detection output detected based on the second wavelength λ2 and the second scattering angle θ2.

[0034] [Smoke identification by the control unit] The control unit 12 shown in FIG. 1 instructs the light emission drive unit 16 to intermittently drive the light emitting element 20 at a predetermined cycle to emit white light including a first wavelength λ1 and a second wavelength λ2, and the backscattered light having a first scattering angle θ1=30° due to the first wavelength λ1 is received by the first light receiving element 22. In response to this, the light receiving output A1 output from the amplifier circuit unit 28 is detected and stored in memory.

[0035] At the same time, since backscattered light with a second scattering angle θ2 = 120° due to the second wavelength λ2 is received by the second light receiving element 24, the control unit 12 detects the light receiving output A2 output from the amplifier circuit unit 26 in response to the light reception by the second light receiving element 24 and stores it in memory.

[0036] Next, the control unit 12 identifies the type of smoke by comparing the light receiving output A1 corresponding to the first light receiving element 22 with the light receiving output A2 corresponding to the second light receiving element 24, and performs a fire judgment based on judgment criteria according to the type of smoke.

[0037] [Determining the type of smoke based on the ratio of received light output] FIG. 3 is an explanatory diagram showing the light receiving output and its ratio detected by the smoke detector structure of FIG. 2 for smoke when a cotton wick and kerosene are burned.

[0038] As shown in Figure 3, the received light output A1 is a received light output of scattered light having a first wavelength λ1 = 700 nm and a first scattering angle θ1 = 30°, and the received light output A2 is a received light output of scattered light having a second wavelength λ2 = 450 nm and a second scattering angle θ2 = 120°.

[0039] If we take the ratio R=A1 / A2 of the received light outputs A1 and A2 measured when burning such a cotton wick and kerosene, then in the case of cotton wick, R=8.0 and in the case of kerosene, R=2.3. This shows a significant difference in the ratio R between the cotton wick and kerosene, making it possible to identify the type of smoke based on the ratio R.

[0040] For this reason, the control unit 12 sets the ratio threshold value Rth1, for example, Rth1=5, and determines that white smoke due to smoldering is occurring if R>5, and determines that black smoke due to combustion is occurring if R<5, and performs control to transmit a fire signal including information indicating the determined type of smoke to the receiver to output a fire alarm.

[0041] [Change ratio threshold] The ratio threshold value Rth1 for identifying the type of smoke shown in Figure 3 can be changed as appropriate depending on the scattering angles θ1, θ2 for the first light receiving element 22 and the second light receiving element 24 provided in the smoke detection unit 18 shown in Figure 2 and the first wavelength λ1 and second wavelength λ2 emitted from the light emitting element 20.

[0042] In addition, in FIG. 3, the ratio threshold value Rth is constant, but the level of smoke discrimination may be changed according to the magnitude of the light receiving outputs A1, A2.

[0043] Fig. 4 is an explanatory diagram showing a setting table for changing the ratio threshold for identifying the type of smoke according to the received light output of the first light receiving element and the second light receiving element. As shown in Fig. 4, the setting table for the ratio threshold is a two-dimensional table of the received light output A1 corresponding to the first light receiving element 22 with the first wavelength λ1 = 700 nm and the first scattering angle θ1 = 30°, and the received light output A2 corresponding to the second light receiving element 24 with the second wavelength λ2 = 450 nm and the second scattering angle θ2 = 120°. For example, as the received light output A1 increases, the ratio threshold Rth1 is changed from 5.0 to 5.2 to 5.5 to determine the type of smoke.

[0044] When the smoke concentration becomes extremely high, it is possible that the ratio threshold Rth1 = 5 set in Figure 3 may be deviated from due to the effects of secondary scattering. To compensate for this, the ratio threshold Rth1 is changed, making it possible to determine the type of smoke with high accuracy.

[0045] [Identifying non-fire factors] FIG. 5 is an explanatory diagram showing a setting table of ratio threshold values ​​for identifying types of smoke and non-fire causes according to the light receiving outputs of the first light receiving element and the second light receiving element.

[0046] As shown in Figure 5, the ratio threshold setting table is a two-dimensional table of the light receiving output A1 corresponding to the first light receiving element 22 and the light receiving output A2 corresponding to the second light receiving element 24, and in addition to the ratio threshold Rth1 = 5 to 5.5 for identifying the type of smoke in Figure 4, a ratio threshold Rth2 = 12 for identifying steam, which is a non-fire cause, is set.

[0047] For example, if steam from a bathroom or the like flows into photoelectric smoke detector 10, a conventional smoke detector would misdiagnose it as smoke from a fire and issue a fire alarm, but in this embodiment, for example, a ratio threshold value Rth2=12 is selected according to the received light output A1, and if R<12, it is identified as fire smoke, and if R>12, it is identified as a non-fire cause such as steam. In this way, when a non-fire cause such as steam is identified, a status signal including non-fire information indicating steam is sent to the receiver, causing the receiver to output a caution alarm rather than a fire alarm.

[0048] [Embodiment of Sensor Control] FIG. 6 is a flow chart showing an embodiment of fire detection control by the circuit block of FIG. 1 using the smoke detector structure of FIG.

[0049] As shown in FIG. 6, in step S1, the control unit 12 instructs the light emission driving unit 16 to intermittently drive the light emitting element 20 using a white LED to emit light at a predetermined cycle to irradiate white light including a first wavelength λ1 and a second wavelength λ2 into the smoke detection unit 18, detects a light receiving output A1 corresponding to the scattered light of the first wavelength λ1 received by the first light receiving element 22 in step S2 and stores it in memory in step S3, and then detects a light receiving output A2 corresponding to the scattered light of the second wavelength λ2 received by the second light receiving element 24 in step S4 and stores it in memory in step S5.

[0050] Next, in step S6, the control unit 12 calculates the ratio R = A1 / A2 of the received light outputs A1, A2, and in step S7 compares the ratio R with a threshold value Rth1 = 5, for example. If the ratio R is equal to or greater than the threshold value Rth1 = 5, in step S8 it compares it with a threshold value Rth2 = 12 for identifying non-fire causes. However, since the ratio R is less than the threshold value Rth2, the process proceeds to step S9 and determines that the fire is a smoldering fire caused by white smoke. If it is determined in step S10 that the received light output A1 is equal to or greater than the threshold value Ath1 corresponding to the smoke concentration that requires a warning alert, the process proceeds to step S11 and transmits a fire signal including white smoke identification information to the receiver and outputs a fire alert indicating that the fire is a smoldering fire caused by white smoke.

[0051] On the other hand, if the ratio R is less than the threshold value Rth1=5 in step S9, the control unit 12 proceeds to step S12 and determines that it is a combustion fire caused by black smoke, and if it determines in step S13 that the light receiving output A2 is equal to or greater than the threshold value Ath2 corresponding to the smoke concentration that requires a warning alarm, the control unit 12 proceeds to step S14 and transmits a fire signal including black smoke identification information to the receiver and outputs a fire alarm indicating that it is a combustion fire caused by black smoke.

[0052] Furthermore, if the control unit 12 determines in step S7 that the ratio R is equal to or greater than the threshold value Rth1=5 and in step S8 that the threshold value Rth2=12, the process proceeds to step S15 and determines that the cause is a non-fire cause such as steam, and if the control unit 12 determines in step S16 that the light receiving output A1 is equal to or greater than the threshold value Ath1 corresponding to the smoke concentration that requires a warning alarm, the process proceeds to step S17 and sends a fire signal including identification information of the non-fire cause to the receiver and outputs a warning alarm or the like indicating that the non-fire alarm is due to a non-fire cause such as steam.

[0053] 6, the ratio of the received light outputs A1, A2 is calculated to determine whether the smoke is white or black each time the white LED is driven to emit light, but smoke may also be identified by calculating the ratio R when the received light output is equal to or greater than a threshold value Ath1 corresponding to the smoke concentration that requires a warning, for example. This eliminates the need to calculate the ratio by detecting and storing the received light outputs A1, A2 in the normal monitoring state, thereby reducing the processing load on the control unit 12 and the current consumption of the photoelectric smoke detector 10.

[0054] [Modifications of the present invention] In the above embodiment, a white LED or a two-color LED is provided as the light emitting element, but an LED emitting a first wavelength λ1 and an LED emitting a second wavelength λ2 may be arranged side by side and driven to emit light simultaneously.

[0055] Furthermore, the present invention includes appropriate modifications that do not impair the objects and advantages of the present invention, and is not limited to the numerical values ​​shown in the above embodiment. [Explanation of symbols]

[0056] 10: Photoelectric smoke detector 11a, 11b: Transmission line 12: Control unit 14: Transmission section 15: Power supply section 16: Light emitting driver 18: Smoke Detection Department 20: Light emitting element 20a, 22a, 24a: Optical axis 22: First light receiving element 24: Second light receiving element 26, 28: Amplification circuit section

Claims

1. a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space; a first light receiving element that receives light of the first wavelength emitted from the light emitting element; a second light receiving element that receives the light of the second wavelength emitted from the light emitting element; Equipped with a ratio between a first light receiving output from the first light receiving element and a second light receiving output from the second light receiving element is compared with a first threshold value to identify the type of smoke that has flowed into the smoke detection space or the type of fire that has generated the smoke, and a ratio between the first light receiving output and the second light receiving output is compared with a second threshold value to identify whether what has flowed into the smoke detection space is smoke or steam; A photoelectric smoke detector characterized in that, when the steam is identified, information indicating that the identification result is steam is transmitted to a fire receiver.

2. 2. The photoelectric smoke detector according to claim 1, A photoelectric smoke detector characterized in that, when the type of smoke is identified, information indicating the type of smoke which is the identification result is transmitted to the fire receiver.

3. A light-emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space; a first light receiving element that receives light of the first wavelength emitted from the light emitting element; a second light receiving element that receives the light of the second wavelength emitted from the light emitting element; Equipped with comparing a ratio of a first light receiving output from the first light receiving element and a second light receiving output from the second light receiving element with a predetermined threshold value to identify whether what has flowed into the smoke detection space is smoke or steam; A photoelectric smoke detector characterized in that, when the steam is identified, information indicating that the identification result is steam is transmitted to a fire receiver.

4. A photoelectric smoke detector as claimed in claim 3, When the smoke is identified, information indicating that the identification result is smoke is transmitted to the fire receiver, thereby outputting a fire alarm; A photoelectric smoke detector characterized in that, when steam is identified, a warning alarm is output by sending information indicating that the identification result is steam to the fire receiver.

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