DETECTOR, DETECTION METHOD, DETECTION SYSTEM, PROGRAM

Abstract

 An objective is to suppress false notification without learning threshold values. The detector (10) includes a first sensor (111), a second sensor (112), a processing device (12), and a notifying device (13). The processing device determines whether a predetermined condition is satisfied with regard to a concentration of smoke measured by the first sensor (111) and a concentration of carbon monoxide measured by the second sensor (112). The processing device (12) selects either a first condition or a second condition as the predetermined condition based on a result of determination of whether a switching condition for the concentration of smoke is satisfied. The first condition is for either the concentration of smoke or the concentration of carbon monoxide. The second condition is for both the concentration of smoke and the concentration of carbon monoxide.

Description

Technical Field

[0001] The present invention generally relates to detectors, detection methods, detection systems, and programs, and particularly relates to a detector for sensing a desired component in air, a detection method performed by the detector, a detection system including the detector, and a program used in the detector.

Background Art

[0002] In the past, there has been proposed a detector for sensing components in air such as carbon monoxide, smoke, and dust. For example, Document 1 (JP 4066761 B2) discloses a fire detector which outputs a fire warning signal warning about the possibility of a fire, based on a monitored concentration of smoke. Document 1 also discloses techniques of determining whether a fire has occurred, by use of a temperature difference in addition to an amount of smoke.

[0003] Document 2 (JP 2006-277138 A) discloses techniques of monitoring concentrations of smoke and carbon monoxide and determining that a fire has occurred when a rate of change in an amount of smoke or a rate of change in an amount of carbon monoxide exceeds a threshold value.

[0004] Document 1 discloses learning of threshold values for the information on smoke and the temperature difference in order to improve reliability of fire detection. Therefore, it may take a relatively long the time to start actual operation.

[0005] In contrast, Document 2 discloses that fire warning is given when a concentration of smoke or carbon monoxide exceeds a threshold value or when the rate of change in the amount of carbon monoxide. In other words, it may be determined that a fire has occurred, when only the concentration of smoke exceeds the threshold value. This may lead to false notification if there is steam or the like.

Summary of Invention

[0006] An objective of the present invention would be to propose a detector capable of suppressing false notification without learning threshold values. Other objectives of the present invention would be to propose a detection method performed by the detector, a detection system including the detector, and a program used in the detector.

[0007] The detector of one aspect in accordance with the present invention includes: a first sensor configured to measure a concentration of smoke in air; a second sensor configured to measure a concentration of carbon monoxide in air; a processing device configured to determine whether a predetermined condition is satisfied with regard to the concentration of smoke measured by the first sensor and the concentration of carbon monoxide measured by the second sensor; and a notifying device configured to output a notification signal when the predetermined condition is satisfied. The processing device is configured to select either a first condition or a second condition as the predetermined condition based on a result of determination of whether a switching condition for the concentration of smoke is satisfied, the first condition being for either the concentration of smoke or the concentration of carbon monoxide, and the second condition being for both the concentration of smoke and the concentration of carbon monoxide.

[0008] The detection method of one aspect in accordance with the present invention includes: obtaining, from a sensing device, a concentration of smoke in air and a concentration of carbon monoxide in air; determining, by a processing device, whether a predetermined condition is satisfied with regard to the obtained concentration of smoke and concentration of carbon monoxide; outputting, from a notifying device, a notification signal when the predetermined condition is satisfied. The method further includes selecting, by the processing device, either a first condition or a second condition as the predetermined condition based on a result of determination of whether a switching condition for the concentration of smoke is satisfied, the first condition being for either the concentration of smoke or the concentration of carbon monoxide, and the second condition being for both the concentration of smoke and the concentration of carbon monoxide.

[0009] The detection system of one aspect in accordance with the present invention includes: the above detector; and a notifier configured to give notice according to the notification signal outputted from the notifying device.

[0010] The program of one aspect in accordance with the present invention is for allowing one or more computers to function as the processing device and the notifying device of the above detector.

Brief Description of Drawings

[0011] 

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is an explanatory diagram of operation of the embodiment.

FIG. 3 is an explanatory diagram illustrating a flow chart of a reading process of the embodiment.

FIG. 4 is an explanatory diagram illustrating a flow chart of a notifying process of the embodiment.

FIG. 5 is an explanatory diagram of operation of the embodiment.

FIG. 6 is an explanatory diagram illustrating a flow chart of part of a fire determination process of the embodiment.

FIG. 7 is an explanatory diagram illustrating a flow chart of other part of a fire determination process of the embodiment.

FIG. 8 is an explanatory diagram illustrating a flow chart of other part of a fire determination process of the embodiment.

FIG. 9 is an explanatory diagram of operation of the embodiment.

FIG. 10 is an explanatory diagram of operation of the embodiment.

FIG. 11 is a diagram of a case where the embodiment applies.

FIG. 12 is a diagram of another case where the embodiment applies.

Description of Embodiments

[0012] As shown in FIG. 1, a detector 10 which is described later, includes a first sensor 111, a second sensor 112, a processing device 12, and a notifying device 13. The first sensor 111 is configured to measure a concentration Cs of smoke in air. The second sensor 112 is configured to measure a concentration Cc of carbon monoxide in air. The processing device 12 is configured to determine whether a predetermined condition is satisfied with regard to the concentration Cs of smoke measured by the first sensor 111 and the concentration Cc of carbon monoxide measured by the second sensor 112. The notifying device 13 is configured to output a notification signal when the predetermined condition is satisfied. The processing device 12 is configured to select either a first condition or a second condition as the predetermined condition based on a result of determination of whether a switching condition for the concentration Cs of smoke is satisfied. The first condition is determined for either the concentration Cs of smoke or the concentration Cc of carbon monoxide. The second condition is determined for both the concentration Cs of smoke and the concentration Cc of carbon monoxide.

[0013] Preferably, the switching condition is that an amount ΔCs of change in the concentration Cs of smoke within a predetermined reference time period equal to or larger than a first determination value Vs2 and the processing device 12 is configured to determine whether the switching condition is satisfied.

[0014] Preferably, the processing device 12 includes a preliminary determiner 1200, a first determiner 1201, and a second determiner 1202. The preliminary determiner 1200 is configured to determine whether the switching condition is satisfied. The first determiner 1201 is configured to determine, without considering the concentration Cc of carbon monoxide, whether the first condition including a condition that the concentration Cs of smoke is equal to or higher than a second determination value Vs1 is satisfied. The second determiner 1202 is configured to determine whether the second condition is satisfied. The second condition includes a condition that the concentration Cs of smoke is equal to or higher than the second determination value Vs1 in addition to a condition that an amount ΔCc of change in the concentration Cc of carbon monoxide within a predetermined reference time period is equal to or larger than a third determination value Vc2. The preliminary determiner 1200 is configured to, when determining that the amount ΔCs of change relating to smoke is smaller than the first determination value Vs2, select the first determiner 1201 and select the first condition as the predetermined condition. The preliminary determiner 1200 is configured to, when determining that the amount ΔCs of change relating to smoke is equal to or larger than the first determination value Vs2, select the second determiner 1202 and select the second condition as the predetermined condition.

[0015] Additionally, the processing device 12 may be configured to cyclically repeat, by the preliminary determiner 1200, a selection process of selecting according to the switching condition. This selection process is a process of selecting the first determiner 1201 when the amount ΔCs of change relating to smoke is determined to be smaller than the first determination value Vs2 and selecting the second determiner 1202 when the amount ΔCs of change relating to smoke is determined to be equal to or larger than the first determination value Vs2. Preferably, the preliminary determiner 1200 is configured to, when a state where the amount ΔCs of change relating to smoke is equal to or larger than the first determination value Vs2 continues for a first determination time period Td1, start a mode of selecting the second determiner 1202 irrespective of the result of determination of whether the switching condition is satisfied. In this case, the preliminary determiner 1200 is configured to instruct the second determiner 1202 to determine whether a condition including a condition that the concentration Cs of smoke is equal to or higher than the second determination value Vs1 in addition to a condition that the amount ΔCc of change relating to carbon monoxide is equal to or larger than the third determination value Vc2 is satisfied. Preferably, the preliminary determiner 1200 is configured to, when a state where the concentration Cs of smoke is smaller than a predetermined threshold value Vs0 continues for a second determination time period Td2, start a mode of selecting either the first determiner 1201 or the second determiner 1202 based on the result of determination of whether the switching condition is satisfied. In this case, more preferably, the second determination time period Td2 is set to a time period longer than the first determination time period Td1.

[0016] The detector 10 may further include a third sensor 113 configured to measure a temperature. In this case, the processing device 12 is configured to determine whether the predetermined condition is satisfied with regard to the temperature measured by the third sensor 113.

[0017] A detection method described below includes: obtaining, from a sensing device 11, a concentration Cs of smoke in air and a concentration Cc of carbon monoxide in air; and determining, by a processing device 12, whether a predetermined condition is satisfied with regard to the obtained concentration Cs of smoke and concentration Cc of carbon monoxide. Additionally, the detection method includes outputting, from a notifying device 13, a notification signal when a result of determination by the processing device 12 indicates that the predetermined condition is satisfied. The predetermined condition judged by the processing device 12 is selected from a first condition and a second condition based on a result of determination of whether a switching condition for the concentration of smoke is satisfied. The first condition is determined for either the concentration Cs of smoke or the concentration Cc of carbon monoxide. The second condition is determined for both the concentration Cs of smoke and the concentration of carbon monoxide.

[0018] The switching condition is that an amount of change in the concentration Vs of smoke within a predetermined reference time period is equal to or larger than a first determination value. The first condition includes a condition that the concentration Cs of smoke is equal to or higher than a second determination value Vs1 is satisfied, but does not include a condition for the concentration Cc of carbon monoxide. Additionally, the second condition includes a condition that the concentration Cs of smoke is equal to or higher than the second determination value Vs1 in addition to a condition that an amount ΔCc of change in the concentration of carbon monoxide within a predetermined reference time period is equal to or larger than a third determination value Vc2. The processing device 12 selects the first condition when the amount ΔCs of change relating to smoke is smaller than the first determination value Vs2. The processing device 12 selects the second condition when the amount ΔCs of change relating to smoke is equal to or larger than the first determination value Vs2.

[0019] Hereinafter, the present embodiment is described in detail. In the present embodiment, the detector 10 is exemplified by a fire detector for sensing a fire. The described fire detector includes a housing (not shown) attached in use to a ceiling of a space to be monitored. This fire detector is of a smoke and heat complex type that determines whether a fire has occurred, by use of three types of information which are a concentration of carbon monoxide (hereinafter referred to as "CO"), a concentration of smoke, and a temperature. In other words, the fire detector is configured to determine whether a fire has occurred, based on monitored CO and smoke which are components in the desired space, and additionally a monitored temperature.

[0020] It is not always necessary to monitor the temperature of the desired space. The techniques of the present embodiment may apply to a detector monitoring only a concentration of CO, in addition to a detector monitoring two types of components which are CO and smoke. Additionally, the fire detector may be configured to detect a fire based on a result of monitoring of ultraviolet rays.

[0021] As shown in FIG. 1, the detector 10 of the present embodiment includes a sensing device 11, the processing device 12, and the notifying device 13. The sensing device 11 includes the first sensor 111 configured to measure a concentration of smoke, the second sensor 112 configured to measure a concentration of CO, and the third sensor 113 configured to measure a temperature. The processing device 12 is configured to perform process described below to determine whether a fire has occurred.

[0022] This detector 10 is used in combination with a notifier 20 to give a detection system. In summary, the detection system includes the detector 10 described below, and the notifier 20 configured to give notice according to the notification signal outputted from the notifying device 13. Thus, when the processing device 12 determines that a fire has occurred, the notifying device 13 outputs the notification signal to the notifier 20. The notifier 20 may include at least one of a device for audio notification such as a buzzer and a voice synthesis device and a device for visual notification such as one or more light emitting diodes and a liquid crystal display. As described above, when the processing device 12 determines that a fire has occurred, the notifying device 13 notifies one or more persons of occurrence of a fire by way of the notifier 20.

[0023] The housing of the fire detector includes inside a space for receiving smoke. The first sensor 111 is of a photoelectric type that includes a light emitting device for emitting light to the space, and a light receiving device for receiving light from the space. The first sensor 111 is configured to measure the concentration of smoke by use of scattering of light caused by smoke. The first sensor 111 is configured to output a value corresponding to a rate of decrease in light, as the concentration of smoke. The first sensor 111 may be not limited to having a configuration using scattering of light caused by smoke, but may have a configuration using a property of smoke not transmitting light. Additionally, the first sensor 111 may not be limited to be of the photoelectric type but may be of an ionization type.

[0024] Principles of measurement of the second sensor 112 are not limited particularly, as long as the second sensor 112 can measure the concentration of CO. However, it is preferable to lower the cost of the second sensor 112, and therefore the second sensor 112 is supposed to an electrochemical sensor in this embodiment. The electrochemical sensor may include a detection electrode containing catalyst, a counter electrode facing the detection electrode, an ion conductor between the detection electrode and the counter electrode. This sensor is configured so that a reaction of water vapor and CO in air with the catalyst in the detection electrode causes movement of charges between the detection electrode and the counter electrode.

[0025] This type of sensor has relatively low sensitivity and accuracy. Therefore, there may be a problem that this type of sensor has difficulty in ensuring detection accuracy when the concentration of CO is relatively low. In summary, when this type of sensor is used, it may be difficult to evaluate the concentration of CO by its absolute value in a range of low concentrations of CO. Note that, there may be other sensors for measuring CO in different principles with high accuracy even in a range of low concentrations. However, such sensors may be relatively expensive and large and thus using such sensors is difficult actually. The detector 10 described below can detect CO from a space if the space has a lower concentration of CO.

[0026] The third sensor 113 is configured to measure a temperature higher than about 50°C. The third sensor 113 may include a thermistor, for example.

[0027] The processing device 12 includes an obtainer 121 configured to obtain information measured by the sensing device 11. The obtainer 121 serves an interface to the sensing device 11. The obtainer 121 converts analog values respectively obtained from the first sensor 111, the second sensor 112, and the third sensor 113 into corresponding digital values. In the following, the digital value corresponding to the first sensor 111 is referred to as a concentration of smoke, and the digital value corresponding to the second sensor 112 is referred to as a concentration of CO, and the digital value corresponding to the third sensor 113 is referred to as a temperature value.

[0028] The processing device 12 includes a main hardware component including a device equipped with one or more processors operating according to a program. This type of device may include an MC (microcontroller) integrated with one or more memories, or a set of a device equipped with one or more processors and external one or more memories. Such a device may also function as the notifying device 13. Therefore, the program allows a computer to function as the processing device 12 and the notifying device 13.

[0029] The program is supposed to be preliminarily stored in a ROM (read only memory). However, the program may be stored in the ROM by use of an assisting device such as a computer connected to the ROM. In this case, the program provided to the assisting device may be supplied through telecommunication lines such as the Internet, or by use of a computer-readable recording medium.

[0030] The processing device 12 further includes a determining device 120 configured to determine whether a fire has occurred, by use of the concentration of CO, the concentration of smoke, and the temperature value. The processing device 12 further includes a clock 122, a storage device 123, and a counter 124. The determining device 120 includes the preliminary determiner 1200, the first determiner 1201, and the second determiner 1202 (see FIG. 1).

[0031] The clock 122 measures the unit time Tu, and the processing device 12 decides a timing of obtaining information from the sensing device 11 based on the unit time Tu. The unit time Tu may be set to one second, for example. The storage device 123 stores therein the information obtained by the obtainer 121 from the sensing device 11, if necessary. Functions of the counter 124 are described later.

[0032] The determining device 120 provided to the processing device 12 performs processes including a reading process S10, a notifying process S20, and a fire determining process S30, as shown in FIG. 2. The reading process S10 is a process of obtaining, by the processing device 12, information from the sensing device 11 by way of the obtainer 121. The notifying process S20 is a process of giving notice of occurrence of a fire by way of the notifying device 13. Additionally, the fire determining process S30 is a process of determining whether a fire has occurred, by use of information obtained from the sensing device 11 in the reading process S10. The fire determining process S30 is performed by the preliminary determiner 1200, the first determiner 1201, and the second determiner 1202 of the determining device 120 (see FIG. 1).

[0033] While a fire has not been occurred, the processes are regularly repeated in the same order of the reading process S10, the notifying process S20, and the fire determining process S30 for each cycle. In other words, processing cycles through a sequence of a link L11, a link L12, and a link L13 for each cycle. Time necessary for one cycle of this sequence may fall within a range of time slightly longer than the unit time Tu. As described later, a time period for one cycle of the sequence of the reading process S10, the notifying process S20, and the fire determining process S30 may contain time periods for various processes, in addition to a time period for waiting the unit time Tu. However, the time periods for the various processes are sufficiently shorter than the time period for waiting. Thus, the time period for one cycle of the sequence of the reading process S10, the notifying process S20, and the fire determining process S30 may fall within a range of time periods similar to the unit time Tu.

[0034] In contrast, when a fire is determined to have occurred in the fire determining process S30, different routes are selected according to timings when the fire is determined to have occurred. Notice of occurrence of a fire may be given through either a route from the fire determining process S30 to the notifying process S20 through the reading process S10, or another route from the reading process S10 to the notifying process S20 through the notifying process S20 and the fire determining process S30. In other words, when a fire is determined to have occurred in the fire determining process S30, notice is given through either a route including the link L13 and the link L11 or another route including the link L11, the link L12 and a link L14. After the notice of occurrence of a fire is given in the notifying process S20, processing returns to the reading process S10 by way of a link L15.

[0035] Hereinafter, the individual processes of the reading process S10, the notifying process S20, and the fire determining process S30 are described in detail. As shown in FIG. 3, in the reading process S10, the determining device 120 obtains the temperature value θ from the third sensor 113 through the obtainer 121 (S11), and obtains the concentration Cs of smoke from the first sensor 111 through the obtainer 121 (S12). The determining device 120 may obtain which one of the temperature value θ and the concentration Cs of smoke before obtaining the other. The obtained concentration Cs of smoke is compared with a threshold value Vs0 (e.g., 1 [%/m]) for determining whether smoke exists (S13). Note that, in the present embodiment, the concentration Cs of smoke is represented by a rate of decrease in light per one meter, and a unit thereof is [%/m].

[0036] When the concentration Cs of smoke is equal to or higher than the threshold value Vs0 (S13: yes), the obtainer 121 obtains the concentration Cc of CO from the second sensor 112 (S15). In contrast, when the concentration Cs of smoke is lower than the threshold value Vs0 (S13: no) and when a count value n has reached a predetermined value Mc (S14: yes), the obtainer 121 obtains the concentration Cc of CO from the second sensor 112 (S15). After the concentration Cc of CO is obtained (S15), the determining device 120 resets the count value n to 1 (S16). Additionally, when the concentration Cs of smoke is lower than the threshold value Vs0 (S13: no) and when the count value n have not yet reached the predetermined value Mc (S14: no), the determining device 120 adds 1 to the count value n (S17).

[0037] In summary, the obtainer 121 obtains the concentration Cc of CO at any of the following timings. When the concentration Cs of smoke is equal to or higher than the threshold value Vs0, the obtainer 121 obtains the concentration Cc of CO irrespective of the count value n. When a state where the concentration Cs of smoke is lower than the threshold value Vs0 continues until the count value n reaches the predetermined value Mc, the obtainer 121 obtains the concentration Cc of CO at a timing when the count value n reaches the predetermined value Mc. In other words, the concentration Cc of CO is obtained immediately when smoke is detected, and the concentration Cc of CO is obtained at a relatively long time interval while smoke is not detected. The time interval at which the obtainer 121 obtains the concentration of CO while smoke is not detected is Mc times longer than a time interval in a case where smoke is detected, and Mc is set in a range of around 3 to 10.

[0038] As described above, the concentration Cs of smoke is obtained, and the concentration Cc of CO is obtained if necessary, and then the reading process S10 ends. After the reading process S10, processing proceeds to the notifying process S20. As shown in FIG. 4, in the notifying process S20, the determining device 120 determines whether a fire has already been determined to have occurred in the fire determining process S30 (S21). As described later, in the fire determining process S30, a fire flag F1 is set to "1" when there is determined to be a probability that a fire has occurred, and the fire flag F1 is set to "0" when a fire is determined to have not occurred.

[0039] When the fire flag F1 is not "1" at step S21 (S21: no), processing proceeds to the fire determining process S30. In contrast, when the fire flag F1 is "1" at step S21 (S21: yes), there would be a high probability that a fire has occurred, and thus the determining device 120 compares the concentration Cs of smoke obtained at step S12 with the (second) determination value Vs1 (S22). The determination value Vs1 is set to a value (e.g., 3.5 [%/m]) larger than the threshold value Vs0.

[0040] When the concentration Cs of smoke is equal to or higher than the determination value Vs1 (S22: yes), notice of a fire is given through the notifying device 13 (S26). Accordingly, when the processing device 12 is informed of a high probability that a fire has occurred, and when the concentration Cs of smoke is equal to or higher than the determination value Vs1, the processing device 12 gives notice of a fire through the notifying device 13.

[0041] When the probability that a fire has occurred is determined to be high (S21: yes) and when the concentration Cs of smoke is lower than the determination value Vs1 (S22: no), the fire flag F1 is reset to "0" (S23) and additionally a count value Ic is also reset to 0 (S24). The count value Ic is used for counting how many times determination described below has been done for the concentration Cc of CO in the fire determining process S30.

[0042] As described above, when the fire flag F1 is "1" at step S21 and there has been determined a probability that a fire has occurred, but when the concentration Cs of smoke does not meet a condition of a fire at subsequent step S22, the determining device 120 determines that a fire has not been occurred. After step S24, processing proceeds to the fire determining process S30, and it is determined whether a fire has occurred.

[0043] In the notifying process S20, the condition required for giving notice of a fire through the notifying device 13 also includes a condition that the fire flag F1 is not "0" after the fire determining process S30 (S25: no). Therefore, the determining device 120 gives notice of a fire through the notifying device 13 when any of the following conditions is satisfied (S26). In summary, when any of one condition that the fire flag F1 is "1" and the concentration Cs of smoke is equal to or higher than the determination value Vs1 and the other condition that the fire flag F1 is not "0" even after the fire determining process S30 is satisfied, the determining device 120 instructs the notifier 20 to give notice of a fire (S26).

[0044] When the fire flag F1 is "0" after the fire determining process S30 (S25: yes), it is determined that a fire has not been occurred. When the fire flag F1 is "0" after the fire determining process S30 (S25: yes), the determining device 120 returns to the reading process S10 after a lapse of the unit time Tu (S27). The unit time Tu may be set to 1 second, for example. When the unit time Tu is set to 1 second, the time interval for obtaining the concentration Cc of CO at step S15 is around Mc seconds in a time period when the state where the concentration Cs of smoke is lower than the threshold value Vs0 continues. Actually, when processing time of the reading process S10, the notifying process S20, and the fire determining process S30 is supposed to be Tp, the time interval for obtaining the concentration Cc of CO is equal to (1 + Tp) × Mc seconds. In this case, Tp is much less than 1, and thus the time interval for obtaining the concentration Cc of CO is substantially equal to Mc seconds.

[0045] In the instance of the notifying process S20 shown in FIG. 4, processing returns to the reading process S10 after a lapse of the unit time Tu (S27) even when notice of a fire is given at step S26. Therefore, after giving notice of a fire at step S26, the determining device 120 returns to the reading process S10 while continuing giving notice of a fire. In summary, notice of a fire is continued once notice of a fire is given.

[0046] Note that, the notifying process S20 may include a process of ending giving notice of a fire when notice of a fire is falsely given. When processing returns to the reading process S10 and subsequently proceeds to the notifying process S20, the fire determining process S30 may be done. In this fire determining process S30, giving notice may be ended when the fire flag F1 becomes "0".

[0047] Next, the fire determining process S30 is described with reference to FIG. 5 to FIG. 8. As shown in FIG. 5, the fire determining process S30 mainly includes three different processes. A preliminary process S31 determines whether there is a probability that a fire has occurred, based on only the temperature value θ obtained from the third sensor 113. A first process S32 determines whether there is a probability that a fire has occurred, based on only the concentration Cs of smoke. A second process S33 determines whether there is a probability that a fire has occurred, based on the concentration Cs of smoke and the concentration Cc of CO. The preliminary process S31 is performed by the preliminary determiner 1200, and the first process S32 is performed by the first determiner 1201, and the second process S33 is performed by the second determiner 1202.

[0048] In summary, to determine whether a fire has occurred, the fire determining process S30 includes the preliminary process S31 using the temperature value θ only, the first process S32 using the concentration Cs of smoke only, and the second process S33 using a combination of the concentration Cc of CO and the concentration Cs of smoke. The second process S33 also includes a process of determining that a fire has not occurred when any of the concentration Cc of CO, the concentration Cs of smoke, and the temperature value θ does not satisfy a corresponding condition. Additionally, the second process S33 includes a process of determining, when any of the concentration Cc of CO, the concentration Cs of smoke, and the temperature value θ does not satisfy a corresponding condition, whether to assign task of determining whether a fire has occurred, to the following fire determining process S30. FIG. 5 shows "confirmed" which means that it is confirmed that a fire has occurred, and "unconfirmed" which means that that it cannot be confirmed that a fire has occurred though there is a possibility that a fire has occurred.

[0049] As shown in FIG. 6, the preliminary determiner 1200 performs the preliminary process S31, thereby comparing the temperature value θ obtained from the third sensor 113 with a determination value Vt1, and also comparing an amount Δθ of change in the temperature value θ within a predetermined reference time period T1 with a determination value Vt2 (S311). For example, when θ(t) represents the temperature value at time t and Δθ(t) represents the amount of change in the temperature value at the time t, Δθ(t) is given by a relation of Δθ(t) = θ(t) - θ(t-T1). The amount Δθ of change is equal to a difference (an absolute value of a difference) between the two temperature values θ obtained at points of time between which an interval is equal to the reference time period T1, that is, points of time of start and end of the reference time period T1.

[0050] Accordingly, dividing the amount Δθ of change by the reference time period T1 gives a temperature gradient. Additionally, provided that the reference time period T1 is set to appropriate unit time (e.g., 60 seconds), the amount Δθ of change is equivalent to the temperature gradient. Therefore, the condition of step S311 may employ the temperature gradient as an alternative to the amount Δθ of change within the reference time period T1.

[0051] For example, the determination value Vt1 for the temperature value θ may be set to around 60 [°C] and the reference time period T1 may be set to be in a range of around 1 to 3 minutes. In other words, the determination value Vt1 is set to a temperature value which is not observed unless a fire has occurred. The reference time period T1 is set based on a length of time in which rise in temperature is observed while a fire occurs.

[0052] Note that, the time interval at which the determining device 120 obtains the temperature value θ from the third sensor 113 is shorter than the reference time period T1 (e.g., the time interval is around 1 second). Therefore, the amount Δθ of change relating to the temperature is obtained after the fire determining process S30 is performed multiple times. The processing device 12 includes the storage device 123, and the storage device 123 includes a storage region for storing the temperature value θ each time the obtainer 121 obtains the temperature value θ from the third sensor 113. With regard to the storage device 123, the storage region for storing the temperature value θ functions equivalent to a shift register, and the amount Δθ of change is calculated as a difference between foremost data (earliest data) and rearmost data (latest data) of a series of data obtained by the reference time period T1.

[0053] At step S311, when at least one of conditions of θ ≥ Vt1 and Δθ ≥ Vt2 is satisfied, a fire is determined to have occurred, and thus the fire flag F1 is set to "1" (S34). In contrast, at step S311, when any of the conditions of θ ≥ Vt1 and Δθ ≥ Vt2 is not satisfied, that is, when θ is smaller than Vt1 and Δθ is smaller than Vt2, it is determined whether a temporary determination flag F2 is "1" (S312).

[0054] The reference time period T1 for calculating the amount Δθ of change is set to be relatively long, and this can facilitate distinguishing the amount Δθ of change in a time period when the temperature value θ sharply rises accompanied with occurrence of a fire from the amount Δθ of change in a time period when change in the temperature value θ is relatively small. Consequently, it is possible to easily determine whether an interested time period is the time period when the temperature value θ sharply rises accompanied with occurrence of a fire, or the time period when change in the temperature value θ is relatively small.

[0055] As described above, the detector 10 further includes the third sensor 113 configured to measure the temperature, and the processing device 12 is configured to determine whether the predetermined condition is satisfied with regard to the temperature measured by the third sensor 113. Thus, the detector 10 can determine whether a fire has occurred, based on the temperature in addition to the concentration Cs of smoke and/or the concentration Cc of CO, and this may lead to improvement of accuracy.

[0056] The temporary determination flag F2 is set to "1" when whether a fire has occurred is unconfirmed and such determination is assigned to the following fire determining process S30. In other words, the temporary determination flag F2 is set to "1" when it cannot be confirmed that a fire has occurred but a probability that a fire has occurred cannot be denied. In contrast, when it can be confirmed that a fire has not occurred, the preliminary determiner 1200 sets the temporary determination flag F2 to "0".

[0057] At step S312, when the temporary determination flag F2 is not "1", the preliminary determiner 1200 compares an amount ΔCs of change in the concentration Cs of smoke within a predetermined reference time period T2 with a (first) determination value Vs2 (S313). When Cs(t) represents the concentration of smoke at the time t and ΔCs(t) represents the amount of change in the concentration Cs of smoke at the time t in a similar manner to the amount Δθ of change in the temperature value θ, ΔCs(t) can be given by a relation ΔCs(t) = Cs(t) - Cs(t-T2). The amount ΔCs of change is equal to a difference (an absolute value of a difference) between the two concentrations Cs of smoke obtained at points of time between which an interval is equal to the reference time period T2, that is, points of time of start and end of the reference time period T2. Accordingly, dividing the amount ΔCs of change by the reference time period T2 gives a concentration gradient relating to smoke. Additionally, provided that the reference time period T2 is set to appropriate unit time (e.g., 60 seconds), the amount ΔCs of change is equivalent to the concentration gradient relating to smoke. Therefore, at step S312 the concentration gradient may be used as an alternative to the amount ΔCs of change within the reference time period T2.

[0058] The reference time period T2 may be set to be in a range of around 30 seconds to 2 minutes. In other words, the reference time period T2 is set to a time period sufficiently longer than the time interval at which the obtainer 121 obtains the concentration Cs of smoke in the reading process S10. However, the amount ΔCs of change is updated every fire determining process S30.

[0059] FIG. 9 shows a relationship among the concentration Cs of smoke, the reference time period T2, and the amount ΔCs of change. This figure also shows a concentration gradient α2 of the concentration Cs of smoke. As shown in the figure, the reference time period T2 is set to be relatively long, and thus it is possible to find out a tendency of change in the concentration Cs of smoke even if the concentration Cs of smoke changes with time.

[0060] Note that, to calculate the amount ΔCs of change in the concentration Cs of smoke within the reference time period T2, the concentration Cs of smoke obtained by the obtainer 121 is stored in the storage device 123 like a case of calculating the amount Δθ of change in the temperature value θ. In detail, the storage device 123 includes a storage region for storing the concentration Cs each time the obtainer 121 obtains the concentration Cs from the first sensor 111. With regard to the storage device 123, the storage region for storing the concentration Cs functions equivalent to a shift register, and the amount ΔCs of change is calculated as a difference between foremost data (earliest data) and rearmost data (latest data) of a series of data obtained by the reference time period T2.

[0061] Note that, at step S312, when the temporary determination flag F2 is "1", it is not confirmed whether a fire has occurred. Thus, it is necessary to confirm whether a fire has occurred in a subsequent process. Accordingly, when a state where the concentration Cs of smoke is lower than the threshold value Vs0 continues for the second determination time period Td2 (S314: yes), the temporary determination flag F2 is set to "0" (S315) to confirm that a fire has not occurred. In other words, when the state where the concentration Cs of smoke is lower than the threshold value Vs0 continues for a time period in which the fire determining process S30 can be performed a number of times corresponding to the determination time period Td2 (S314: yes), the preliminary determiner 1200 sets the temporary determination flag F2 to "0" (S315).

[0062] The determination time period Td2 is set to a time period sufficiently longer than a cycle (e.g., around 1 seconds) at which the determining device 120 obtains the concentration Cs of smoke from the first sensor 111, and may be set to 60 seconds, for example. If the reading process S10, the notifying process S20, and the fire determining process S30 are repeated at a cycle of about 1 second, the determination time period Td2 is equivalent to time taken for the fire determining process S30 to be performed sixty times. The threshold value Vs0 is a lower limit value for determining that smoke has occurred, and thus is smaller than the determination value Vs1 for determining that fire has occurred (e.g., Vs0 ≈ 0.3 × Vs1).

[0063] At step S314, when the state where the concentration Cs of smoke is lower than the threshold value Vs0 does not continue for the determination time period Td2 (S314: no), processing proceeds to the second process S33. In other words, when the concentration Cs becomes equal to or higher than the threshold value Vs0 before a lapse of the determination time period Td2, processing proceeds to the second process S33. At step S313, when the amount ΔCs of change in the concentration Cs of smoke is smaller than the determination value Vs2 (or the concentration gradient α2 relating to smoke is relatively low), processing proceeds to the first process S32. Further, at step S313, when the amount ΔCs of change is equal to or larger than the determination value Vs2 (or the concentration gradient α2 relating to smoke is relatively high), process proceeds to the second process S33.

[0064] In brief, the condition [ΔCs ≥ Vs2] at step S313 in the preliminary process S31 serves as a switching condition for determining which of the first process S32 and the second process S33 is selected. In summary, the switching condition is that the amount ΔCs of change in the concentration Cs of smoke within the predetermined reference time period is equal to or larger than the first determination value Vs2, and the preliminary determiner 1200 determines whether the switching condition is satisfied. In other words, the preliminary determiner 1200 performs determination based on the switching condition relating to whether the amount ΔCs of change in the concentration Cs of smoke within the predetermined reference time period is smaller than the first determination value Vs2. When the condition at step S313 is not satisfied (S313: no), the processing device 12 selects the first process S32. When the condition at step S313 is satisfied (S313: yes), the processing device 12 selects the second process S33.

[0065] The first process S32 and the second process S33 use a count value as described later. Hence, the processing device 12 includes the counter 124 configured to provide the count value. This counter 124 can increment and decrement the count value, and the minimum value of the count value is 0. When the fire flag F1 is set to "0" in the notifying process S20 (S23) or when the temporary determination flag F2 is set to "0" in the fire determining process S30 (S315), the count value of the counter 124 is reset to 0. The counter 124 is configured to provide the count value representing a continuous time period in which detection of smoke continues and the count value representing a continuous time period in which detection of CO continues.

[0066] The first determiner 1201 configured to perform the first process S32 illustrated in FIG. 7 determines whether a fire has occurred, based on the concentration Cs of smoke only, as described above. The first determiner 1201 employs a prerequisite that the temporary determination flag F2 is "0" (S312: no, or S315) and the amount ΔCs of change in the concentration Cs of smoke is smaller than the determination value Vs2 (ΔCs < Vs2) (S313: no). This prerequisite means that a fire has not occurred and change in the concentration Cs of smoke in the determination time period Td2 has not been detected. In other words, satisfying the prerequisite of the first process S32 indicates that there is a high probability that a fire has not occurred.

[0067] The condition for the first determiner 1201 to determine that a fire has occurred is that a state where the concentration Cs of smoke is high continues for a relatively long time period (e.g., around 10 seconds). The continuous time period in which detection of smoke continues is not limited to a time period in which the state where the concentration Cs of smoke obtained by the obtainer 121 is high is continuous. When the state where the concentration Cs is high is discontinuous but the state where the concentration Cs of smoke is high is considered continuous, the counter 124 provides the count value representing the continuous time period.

[0068] In the first process S32, the first determiner 1201 compares the concentration Cs of smoke obtained by the reading process S10 with the determination value Vs1 (S321). When the concentration Cs of smoke is equal to or higher than the determination value Vs1 (S321: yes), the counter 124 increments the count value Is corresponding to smoke by one (S322). In contrast, when the concentration Cs of smoke is lower than the determination value Vs1 (S321: no), the count value Is is decremented by two (S323). The count value Is is used for estimation of the continuous time period.

[0069] The count value Is is compared with a reference value Ns (S324). When the count value Is is larger than the reference value Ns (S324: yes), the first determiner 1201 determines that the state where the concentration Cs of smoke is equal to or higher than the determination value Vs1 has continued, and sets the fire flag F1 to "1" (S34). Note that, when the count value Is is smaller than the reference value Ns (S324: no), the determining device 120 starts the notifying process S20.

[0070] The continuous time period is time taken for the count value Is to reach the reference value Ns. Hence, the concentration Cs of smoke is allowed to be lower than the determination value Vs1 before the continuous time period reaches the reference value Ns. This is because the concentration Cs of smoke varies with time and therefore the concentration Cs of smoke is likely to be lower than the determination value Vs1 temporary after the concentration Cs of smoke has been equal to or higher than the determination value Vs1 due to a fire. As described above, even if the concentration Cs becomes low temporary, monitoring of the concentration Cs of smoke is continued. Therefore, as long as the concentration Cs of smoke continuously corresponds to a case where a fire has occurred continues, a fire is determined to have occurred. Consequently, failure in notification can be suppressed.

[0071] In contrast, there may be a probability that the concentration Cs of smoke becomes equal to or higher than the determination value Vs1 temporary due to smoking, cooking, or the like. However, the count value Is does not reach the reference value Ns. Therefore, as long as the reference value Ns is set appropriately, false notification can be suppressed. Additionally, when the concentration Cs of smoke is lower than the determination value Vs1, the count value Is is decremented by two (S323). When the concentration Cs of smoke is low, time taken for the count value Is to reach the reference value Ns increases. Therefore, effects of suppressing false notification can be expected.

[0072] The second determiner 1202 configured to perform the second process S33 uses the concentration Cc of CO in addition to the concentration Cs of smoke in order to determine whether a fire has occurred. There are two types of prerequisites for the second process S33, and the second process S33 is executed when any one of these is satisfied. One of the prerequisites is that the temporary determination flag F2 is "0" (S312: no) and the amount ΔCs of change in the concentration Cs of smoke is equal to or larger than the determination value Vs2 (ΔCs ≥ Vs2) (S313: yes). The other of the prerequisites is that the temporary determination flag F2 is "1" (S312: yes) and the state where the concentration Cs of smoke is lower than the threshold value Vs0 does not continue for the determination time period Td2 (S314: no). In terms of the second process S33, both of the prerequisites include a condition for the concentration Cs of smoke.

[0073] After step S313 or step S314 (S313: yes, or S314: no), the second determiner 1202 configured to perform the second process S33 illustrated in FIG. 8 compares the amount ΔCc of change in the concentration Cc within a predetermined reference time period T3 with the (third) determination value Vc2 (S331). The reference time period T3 is set to be in a range of about 30 seconds to 2 minutes like the reference time period T2. The amount ΔCc of change is updated every fire determining process S30.

[0074] Note that, the concentration Cc of CO is not equal to the concentration Cc obtained by the obtainer 121 in the reading process S10, but is equal to a moving average of the concentration Cc. The number of concentrations Cc for calculating the moving average may be in a range of about 5 to 15, preferably. In other words, the concentration Cc of CO does not correspond to an actual value obtained by the obtainer 121, but corresponds to an average of the predetermined number of concentrations Cc obtained within a predetermined time period prior to time of calculating the concentration Cc.

[0075] For example, the concentrations Cc of CO are supposed to be obtained by the obtainer 121 at a series of time points C1, C2, ......, Cm. When the moving average calculated based on twelve concentrations is used as the concentration Cc of CO, the moving averages of the concentration Cc are (C1 + C2 + ... + C12)/12, (C2 + C3 + ... + C13)/12, (C3 + C4 + ... + C14)/12, ... .

[0076] The concentration Cc of CO is given by the moving average, and it is thus possible to detect at high accuracy change in the concentration Cc of CO even if the second sensor 112 for measuring the concentration of CO is an electrochemical sensor with relatively low measurement accuracy.

[0077] For example, when CO is derived from a fire, the concentration gradient of CO falls within at least a range of about 1 to 5 ppm/min. When the second sensor 112 is an electrochemical sensor, the concentration gradient can be calculated from adjacent concentrations Cc included in a time series of data on the concentration Cc of CO obtained every reading process S10. However, such a concentration gradient cannot give sufficient accuracy to an extent available for detection of a fire.

[0078] In contrast, in the present embodiment, with regard to the concentration Cc of CO, the amount ΔCc of change in the concentration Cc is calculated by use of the moving average method, and it is determined whether a fire has occurred, based on the calculated amount ΔCc of change. Therefore, it is easy to detect change in the concentration Cc of CO at high accuracy.

[0079] When the amount ΔCc of change in the concentration Cc of CO is equal to or larger than the determination value Vc2 (S331: yes), the counter 124 increments the count value Ic associated with CO by one (S332), and subsequently the concentration Cs of smoke is compared with the determination value Vs1 (S334).

[0080] When Cc(t) represents the concentration of CO at the time t and ΔCc(t) represents the amount of change in the concentration Cc of CO at the time t in a similar manner to the amount ΔCs of change in the concentration Cs of smoke, ΔCc(t) can be given by a relation ΔCc(t) = Cc(t) - Cc(t-T3). The amount ΔCc of change is equal to a difference (an absolute value of a difference) between the two concentrations Cc of CO obtained at points of time between which an interval is equal to the reference time period T3, that is, points of time of start and end of the reference time period T3. Note that, the reference time period T3 may be equal to or different from the reference time period T2.

[0081] Dividing the amount ΔCc of change by the reference time period T3 gives a concentration gradient of CO. Therefore, provided that the reference time period T3 is set to appropriate unit time (e.g., 60 seconds), the amount ΔCc of change is equivalent to the concentration gradient. Therefore, at step S331, the concentration gradient may be used as an alternative to the amount ΔCc of change within the reference time period T3. As described above, the reference time period T3 is set to be almost equal to the reference time period T2. Additionally, to facilitate internal processing of the processing device 12, the reference time period T3 may be preferably equal to the reference time period T2.

[0082] FIG. 10 shows a relationship among the concentration Cc of CO, the reference time period T3, and the amount ΔCc of change. This figure also shows a concentration gradient α3 of the concentration Cc of CO. As shown in the figure, even if the accuracy of the concentration Cc within the reference time period T3 is insufficient, it is possible to detect change in the concentration Cc of CO when the reference time period T3 is set appropriately and there is a relatively large change in the concentration Cc of CO.

[0083] Note that, when the concentration Cs of smoke is equal to or higher than the determination value Vs1 at step S334 (S334: yes), the count value Is associated with smoke is incremented by one (S335). Or, when the concentration Cs of smoke is lower than the determination value Vs1 (S334: no), the count value Is associated with smoke is decremented by two (S336). Step S334 to S336 are the same as steps S321 to S323 in the first process S32. After the count value Is is decremented by two at step S336, the determining device 120 starts the notifying process S20.

[0084] After step S335, the second determiner 1202 compares the count value Ic associated with CO with a reference value Nc (S337). When the count value Ic is equal to or larger than the reference value Nc (S337: yes), the count value Is associated with smoke is also compared with the reference value Ns (S338). When the count value Is is equal to or larger than the reference value Ns (S338: yes), the second determiner 1202 sets the fire flag F1 to "1" (S34). When the count value Ic is smaller than the reference value Nc (S337: no) or when the count value Is is smaller than the reference value Ns (S338: no), the determining device 120 starts the notifying process S20.

[0085] In the second process S33 illustrated in FIG. 8, when the amount ΔCc of change in the concentration Cc of CO is smaller than the determination value Vc2 at step S331 (S331: no), the counter 124 decrements the count value Ic associated with CO by two (S333). Further, after step S333, it is determined whether the state where the amount ΔCs of change in the concentration Cs of smoke is equal to or larger than the determination value Vs2 continues for a (first) determination time period Td1 (S339).

[0086] When the state where the amount ΔCs of change in the concentration Cs of smoke is equal to or larger than the determination value Vs2 continues for a time period in which the fire determining process S30 is performed a number of times corresponding to the determination time period Td1 (S339: yes), the temporary determination flag F2 is set to "1" (S340). When a time period in which the state where the amount ΔCs of change in the concentration Cs of smoke is equal to or larger than the determination value Vs2 continues does not reach the determination time period Td1 or after step S340, the determining device 120 starts the notifying process S20 again.

[0087] The determination time period Td1 is set in order to identify the continuous time period of a state where the concentration Cs of smoke increases sharply. When smoke is caused by a fire, a situation where the concentration Cs of smoke increases sharply continues for more than about 10 seconds. Hence, the determination time period Td1 is set to around 10 seconds. In other words, the (second) determination time period Td2 used by the preliminary determiner 1200 is set to a time period longer than the (first) determination time period Td1 used by the second determiner 1202.

[0088] As described above, in the fire determining process S30, the preliminary process S31 determines whether a fire has occurred, based on the temperature value θ, and additionally defines the prerequisites for the first process S32 and the second process S33. The prerequisite for the first process S32 is that change in the concentration Cs of smoke is small (ΔCs < Vs2) while a fire is determined to have occurred (F2 = 0). There are two types of prerequisites defined for the second process S33. The first one of the prerequisites is that the concentration Cs of smoke increases sharply (ΔCs ≥ Vs2) while a fire is determined to have not occurred (F2 = 0). The second one of the prerequisites is that it is not confirmed whether a fire has occurred (F2 = 1) and the state where the concentration Cs of smoke is lower than the threshold value Vs0 does not continue for the determination time period Td2 (S314: no).

[0089] As described above, the preliminary determiner 1200 compares the amount ΔCs of change in the concentration Cc of smoke with the first determination value Vs2 at step S313. The preliminary determiner 1200 selects the first determiner 1201 when a relation of ΔCs < Vs2 is satisfied, and selects the second determiner 1202 when a relation of ΔCs ≥ Vs2 is satisfied. The first determiner 1201 performs determination with regard to the concentration Cs of smoke without taking into account the concentration Cs of carbon monoxide. In contrast, the second determiner 1202 performs determination with regard to the concentration Cs of smoke in addition to the amount ΔCc of change in the concentration Cc of carbon monoxide.

[0090] In summary, the detector 10 selects, as the condition for subsequent determination, either a first condition for either the concentration Cs of smoke or the concentration Cc of carbon monoxide, or a second condition for both the concentration Cs of smoke and the concentration Cc of carbon monoxide, based on a result of determination of the switching condition. Accordingly, when there is difficulty in performing the determination by use of the concentration Cs of smoke only, the detector 10 can additionally use the concentration Cc of carbon monoxide for the determination. Consequently, it is possible to suppress false notification without learning threshold values.

[0091] Additionally, the processing device 12 sets the temporary determination flag F2 to "1" when the state where the amount ΔCs of change in the concentration Cs of smoke is equal to or larger than the (first) determination value Vs2 continues for the first determination time period Td1 in the second process S33. As a result, the preliminary determiner 1200 terminates the process of comparing the amount ΔCs of change in the concentration Cs of smoke with the first determination value Vs2. Consequently, the second determiner 1202 continues the second process S33.

[0092] In summary, when the state where the amount ΔCs of change relating to smoke is equal to or larger than the first determination value Vs2 continues for the first determination time period Td1, the preliminary determiner 1200 proceeds to a mode of selecting the second determiner 1202 irrespective of the result of determination of whether the switching condition is satisfied. In other words, when the state where the amount ΔCs of change relating to smoke is equal to or larger than the first determination value Vs2 continues for the first determination time period Td1, the processing device 12 proceeds to a mode in which the preliminary determiner 1200 selects the second determiner 1202 irrespective of whether the switching condition is satisfied. In short, the processing device 12 proceeds to a mode of the temporary flag F2 being "1". When the state where the concentration Cs of smoke is smaller than the predetermined threshold value Vs0 continues for the second determination time period Td2 in this mode, the preliminary determiner 1200 proceeds to a mode of selecting either the first determiner 1201 or the second determiner 1202 based on the result of determination of whether the switching condition is satisfied. In other words, when the state where the concentration Cs of smoke is smaller than the predetermined threshold value Vs0 continues for the second determination time period Td2, the processing device 12 proceeds to a mode in which the preliminary determiner 1200 selects either the first determiner 1201 or the second determiner 1202 based on the result of determination of whether the switching condition is satisfied. In short, the processing device 12 proceeds to a mode of the temporary flag F2 being "0".

[0093] The preliminary process illustrated in FIG. 6 is defined so that, when the temporary flag F2 is "1", the preliminary determiner 1200 does not determine whether the switching condition (ΔCs ≥ Vs2) is satisfied. However, the preliminary determiner 1200 may determine whether the switching condition is satisfied. Note that, even in a case where the preliminary determiner 1200 determines whether the switching condition is satisfied, the preliminary determiner 1200 still selects the second determiner 1202 irrespective of whether the switching condition is satisfied, as long as the temporary flag F2 is "1". This operation obviously indicates that the temporary flag F2 functions to inform the preliminary determiner 1200 of a result of determination that the condition judged by the second determiner 1202 (the relation of ΔCs ≥ Vs2 continues for the determination time period Td1) is satisfied.

[0094] The second determiner 1202 determines whether a condition is satisfied, this condition including a condition that the concentration Cs of smoke is equal to or higher than the (second) determination value Vs1 in addition to a condition that the amount ΔCc of change in the concentration Cc of carbon monoxide is equal to or larger than the (third) determination value Vc2. Note that, when the state where the concentration Cs of smoke is lower than the threshold value Vs0 continues for the (second) determination time period Td2, the preliminary determiner 1200 returns to the mode of selecting either the first determiner 1201 or the second determiner 1202 according to the switching condition. In the example of operation illustrated in FIG. 6, at step S313, the preliminary determiner 1200 returns to a mode in which the process of comparing the amount ΔCs of change in the concentration Cs of smoke with the (first) determination value Vs2 is performed.

[0095] Note that, in the meaning of numerical values, the threshold value Vs0 is determined based on the determination value Vs1 for the concentration Cs of smoke and the determination value Vs2 for the amount ΔCs of change in the concentration Cs of smoke so as to satisfy a relation of Vs0 < Vs1 - Vs2. This is because of suppressing the concentration Cs of smoke from being equal to or higher than the determination value Vs1 immediately after the preliminary determiner 1200 switches the temporary determination flag F2 from "1" to "0" and thereby returns to the process passing through step S313. In a case where the threshold value Vs0 is equal to or larger than Vs1 - Vs2, Vs0 + Vs2 is equal to or larger than the determination value Vs1 even if the amount ΔCs of change is smaller than the determination value Vs2 at step S313. Thus, the concentration Cs of smoke is equal to or higher than the determination value Vs1, and thereby the count value Is associated with smoke is incremented by one. In contrast, in the present embodiment, the threshold value Vs0 is equal to or smaller than Vs1 - Vs2, and therefore Vs0 + Vs2 is smaller than the determination value Vs1 at step S313. Hence, increment of the count value Is associated with smoke can be suppressed.

[0096] A state of a fire may vary according to various causes such as types of substances burning in a fire and environments of places where a fire has occurred. The state of a fire is categorized into about ten types. There are known cases relating to time variations of the concentration Cs of smoke and the concentration Cc of CO due to a fire. In one of the cases the concentration Cs of smoke and the concentration Cc of CO increase sharply in a short time, and in the other of the cases the concentration Cs of smoke and the concentration Cc of CO increase gradually in a relatively long time. Additionally, the concentrations Cs and Cc may increase to relatively high values, or increase to only relatively low values, or be saturated, or increase and then decrease, depending on the state of a fire.

[0097] Additionally, time from occurrence of a fire to start of increase in the concentrations Cs and Cc may vary depending on the state of a fire. In some cases, the concentration Cs of smoke and the concentration Cc of CO may start to increase at different timings. Generally, it is known that timings of start of increase in the concentration Cs of smoke and the concentration Cc of CO appear to have similar tendencies. Note that, fire detectors need to detect a fire within about 10 minutes from occurrence of the fire. As mentioned in the above, fire detectors need to determine, within about 10 minutes, whether a fire has occurred, with regard to various states of fires.

[0098] In the aforementioned configuration example, the first process S32 in the fire determining process S30 allows detection of occurrence of a fire in a state where the concentration Cs of smoke continuously and gradually increases. Further, a fire in a state where the concentration Cs of smoke increases sharply can be detected by the second process S33. In the second process S33, it is determined, referring to an increasing tendency of the first process S32, whether a fire causing a sharp increase in the concentration Cs of smoke has occurred. If the concentration Cc of CO is relatively low, a fire can be determined to have occurred provided that the amount ΔCc of change in the concentration Cc of CO is equal to or larger than the determination value Vc2.

[0099] In summary, when the concentration Cc of CO is relatively low but the amount ΔCc of change in the concentration Cc of CO is relatively large, the second process S33 allows judgement of a fire while repeating the fire determining process S30 multiple times. In this process, the condition for determining that a fire has occurred includes a condition that the state where the concentration Cs of smoke is equal to or higher than the determination value Vs1 continues. To sum up, a fire determined to have occurred by the second process S33 may be in a state where the state where the concentration Cs of smoke is relatively high continues and the concentration Cs of smoke increases sharply and the state where the concentration Cc of CO increases also continues.

[0100] The second process S33 does not determine that a fire has occurred, when the state where the concentration Cs of smoke sharply increases can continue for only a short time and the amount ΔCc of change in the concentration Cc of CO is relatively small. Such a situation may be supposed to occur due to white smoke caused by dry ice, steam, or the like. Thus, the second process S33 can distinguish smoke caused by a fire from white smoke caused by dry ice or steam.

[0101] In short, when the amount ΔCc of change in the concentration Cc of CO is relatively small but the state where the concentration Cs of smoke sharply increases continues for a relatively long time, it is difficult to deny a probability that a fire has occurred. Therefore, in such a case, the temporary determination flag F2 is set to "1", and confirmation of the result of determination is appointed to the subsequent fire determining process S30.

[0102] FIG. 11 shows an example of change in the measurement value (the concentration Cs) in a case where the first sensor 111 measures steam generated by an electric pot (so-called "electric kettle") with no heat retention function. In this figure, time from start of increase in the concentration Cs of smoke to the time t4 is about 6 minutes. Further, in the figure, the maximum of the concentration Cs is about 15 %/m.

[0103] Note that, in the example shown in FIG. 11, the concentration Cs of smoke is supposed to be equal to or higher than the threshold value Vs0 during an almost entire time period to the time t4. In this example, at step S311 in the fire determining process S30, the temperature value θ does not satisfy the condition for determining that a fire has occurred. In summary, processing proceeds to step S312 from step S311.

[0104] Further, in the example illustrated in the figure, in a time period from the concentration Cs being equal to or higher than the threshold value Vs0 due to start of generation of steam to the time t3, the concentration Cs increases. In a time period from the time t3 to the time t4, the concentration Cs decreases. Further, the time t1 represents a point of time at which the condition (the relation of ΔCs ≥ Vs2 continues for the determination time period Td1) of step S339 in the fire determining process S30 is satisfied, and at this point of time the temporary determination flag F2 becomes "1". The time t2 subsequent to the time t1 represents a point of time at which the condition (the relation of Cs < Vs0 continues for the determination time period Td2) of step S314 is satisfied. Accordingly, the time t1 corresponds to a point of time at which the determination time period Td1 elapses after the concentration Cs of smoke is equal to or higher than the threshold value Vs0. The time t2 corresponds to a point of time at which the determination time period Td2 elapses thereafter.

[0105] In the example illustrated in the figure, when the condition (Cs ≥ Vs0) of step S13 in the reading process S10 is satisfied and subsequently the condition (ΔCs ≥ Vs2) of step 313 in the fire determining process S30, processing proceeds to the second process S33. Note that, until the time t1, the condition (the relation of ΔCs ≥ Vs2 continues for the determination time period Td1) of step S339 is not satisfied and therefore processing passes through steps S312 and S313 and thereby the second process S33 is selected.

[0106] When this state continues until the determination time period Td1 passes, the condition of step S339 is satisfied, and thereby the temporary determination flag F2 is set to "1". Therefore, in the subsequent fire determining process S30, the condition (F2 = 1) of step S312 is satisfied and thus step S314 is selected. In this regard, since the state where the concentration Cs of smoke is high continues, the condition (the relation Cs < Vs0 continues for the determination time period Td2) of step S314 is not satisfied, and the state where the temporary determination flag F2 is kept to be "1", and thus the second process S33 is selected (see FIG. 6).

[0107] This state continues until the temporary determination flag F2 becomes "0". After the time t3, the concentration Cs of smoke further decreases after the time t3 and thus the condition (the relation of ΔCs ≥ Vs2 continues for the determination time period Td1) of step S339 is not satisfied. However, the temporary determination flag F2 is kept to be "1". Hence, the condition (F2 = 1) of step S312 is satisfied but the condition (the relation of Cs < Vs0 continues for the determination time period Td2) of step S314 is not satisfied. Hence, the second process S33 is still selected even after the time t3.

[0108] At the time t4, the condition (F2 = 1) of step S312 is satisfied and further the condition (the relation of Cs < Vs0 continues for the determination time period Td2) of step S314 is also satisfied. Thus, processing proceeds to step S315 and therefore the temporary determination flag F2 becomes "0". Thereafter, by way of step S313 the first process S32 is selected. However, the concentration Cs of smoke already decreases, and hence the condition (Cs ≥ Vs1) of step S321 is not satisfied and the count value Is associated with smoke is not incremented. Accordingly, the condition (Is ≥ Vs1) of step S324 is not satisfied, and thus the fire flag F1 does not become "1". This can lead to avoidance of occurrence of false notification.

[0109] In summary, in a case where CO is absent a similar to a case of steam from an electric pot, the fire determining process S30 mainly selects the second process S33. When CO is not detected, the temporary determination flag F2 becomes "1", and a state where steam is temporary determined to have occurred continues. While the temporary determination flag F2 is "1", step S313 is not selected until the concentration Cs of smoke becomes lower than the threshold value Vs0. Therefore, always the second process S33 is selected. As a result, while CO is not detected, the state where the temporary determination flag F2 is "1" and then the second process S33 is selected is maintained until the concentration Cs of smoke decreases. Hence, occurrence of false notification can be suppressed.

[0110] In a supposed case where the temporary determination flag F2 is not used in the fire determining process S30, the determination at step S313 is performed always. In this case, even if the concentration Cs of smoke starts to decrease at the time t3, the condition (ΔCs ≥ Vs2) of step S313 is no longer satisfied and thus processing proceeds to the first process S32 and accordingly the condition (Cs ≥ Vs1) of step S321 is satisfied. As a result, the count value Is associated with smoke is incremented every fire determining process, and finally the fire flag F1 becomes "1". Thus, the notifying process S20 gives notice of a fire through the notifying device 13 (S26), and this may lead to false notification. According to the configuration of the present embodiment, the aforementioned scheme can suppress such false notification.

[0111] FIG. 12 shows an example in which the concentration Cs of smoke varies periodically. In the example illustrated in the figure, a state where the concentration Cs of smoke becomes temporarily high appears periodically. In summary, the concentration Cs of smoke illustrated in the figure varies so as to show a bell-shape at a cycle Tp. The concentration Cs of smoke has its local maximum at the cycle Tp, and a difference ΔCp between local maximum values becomes relatively small. Note that, in the example illustrated in the figure, it is supposed that the local maximum values of the concentration Cs of smoke are equal to or larger than the determination value Vs1 and the cycle Tp and the determination time period Td2 satisfy a relation of Tp ≈ Td2. Additionally, the cycle Tp is supposed to be almost equal to the reference time periods T2 and T3.

[0112] When the concentration Cs of smoke varies as shown in FIG. 12, there is a high probability that smoke is not caused by a fire. According to the present embodiment, when the concentration Cs of smoke varies as shown in FIG. 12, the condition (the state in which Cs < Vs0 continues for the determination time period Td2) of step S314 in the fire determining process S30 is not satisfied, and thus processing proceeds to the second process S33. When CO is not detected, processing passes through step S339 but the condition (the state in which ΔCs ≥ Vs2 continues for the determination time period Td1) of step S339 is not satisfied and accordingly each of the fire flag F1 and the temporary determination flag F2 is kept to be "0".

[0113] Alternatively, when CO is detected, processing may pass through step S334 but the concentration Cs of smoke varies periodically. Hence, the concentration Cs of smoke does not continuously satisfy the condition (Cs ≥ Vs1) of step S334. Accordingly each of the fire flag F1 and the temporary determination flag F2 is kept to be "0".

[0114] As described above, when the concentration Cs of smoke varies periodically as shown in FIG. 12, a fire is not determined to have occurred, and thus occurrence of false notification can be suppressed. Similarly, even if steam from a bathroom continuously stays in an undressing room or dust stays for a long time, CO is not detected and thus occurrence of false notification can be suppressed.

[0115] Note that, in the aforementioned configuration example, the second sensor 112 for measuring the concentration of CO is an electrochemical sensor, and uses a moving average of the concentration Cc of CO to calculate the amount ΔCc of change in the concentration Cc of CO. However, if the second sensor 112 has relatively high measurement accuracy, it is allowed to use a configuration of using the amount ΔCc of change directly calculated from the concentration Cc measured by the second sensor 112 instead of the moving average of the concentration Cc of CO. Additionally, the reference time period T2 is set to be equal to the time interval at which the obtainer 121 obtains the concentration Cs of smoke from the first sensor 111, and the reference time period T3 is set to be equal to the time interval at which the obtainer 121 obtains the concentration Cc of smoke from the second sensor 112. However, these time periods may be extended appropriately.

[0116] The aforementioned configuration example may preferably perform an additional reset process in case false notification occurs.

[0117] Note that, in the aforementioned configuration example, it is supposed that the notifier 20 operates according to the notification signal outputted from the notifying device 13 and the sensing device 11, the processing device 12, the notifying device 13, and the notifier 20 are accommodated in a common housing. However, the notifier 20 may be accommodated in a separate housing and the notifying device 13 may output the notification signal to the notifier 20 through telecommunications.

[0118] Further, the notifier 20 may be replaced with a receiver for monitoring occurrence of a fire, and the receiver may be connected to multiple fire detectors so that the multiple fire detectors output their own notification signals to the receiver. Such a receiver has functions of managing the multiple fire detectors intensively and monitoring whether a fire has occurred for each of individual places where the multiple fire detectors are installed.

Claims

1. A detector comprising:

a first sensor configured to measure a concentration of smoke in air;

a second sensor configured to measure a concentration of carbon monoxide in air;

a processing device configured to determine whether a predetermined condition is satisfied with regard to the concentration of smoke measured by the first sensor and the concentration of carbon monoxide measured by the second sensor; and

a notifying device configured to output a notification signal when the predetermined condition is satisfied,

the processing device being configured to select either a first condition or a second condition as the predetermined condition based on a result of determination of whether a switching condition for the concentration of smoke is satisfied, the first condition being for either the concentration of smoke or the concentration of carbon monoxide, and the second condition being for both the concentration of smoke and the concentration of carbon monoxide.

2. The detector of claim 1, wherein:

the switching condition is that an amount of change in the concentration of smoke within a predetermined reference time period is equal to or larger than a first determination value; and

the processing device is configured to determine whether the switching condition is satisfied.

3. The detector of claim 2, wherein:

the processing device includes

a preliminary determiner configured to determine whether the switching condition is satisfied,

a first determiner configured to determine, without considering the concentration of carbon monoxide, whether the first condition including a condition that the concentration of smoke is equal to or higher than a second determination value is satisfied, and

a second determiner configured to determine whether the second condition is satisfied, the second condition including a condition that the concentration of smoke is equal to or higher than the second determination value in addition to a condition that an amount of change in the concentration of carbon monoxide within a predetermined reference time period is equal to or larger than a third determination value; and

the preliminary determiner is configured to,

when determining that the amount of change relating to smoke is smaller than the first determination value, select the first determiner and select the first condition as the predetermined condition, and

when determining that the amount of change relating to smoke is equal to or larger than the first determination value, select the second determiner and select the second condition as the predetermined condition.

4. The detector of claim 3, wherein:

the processing device is configured to cyclically repeat, by the preliminary determiner, a process of selecting the first determiner when the amount of change relating to smoke is determined to be smaller than the first determination value and selecting the second determiner when the amount of change relating to smoke is determined to be equal to or larger than the first determination value; and

the preliminary determiner is configured to, when a state where the amount of change relating to smoke is equal to or larger than the first determination value continues for a first determination time period, proceed to a mode of selecting the second determiner irrespective of the result of determination of whether the switching condition is satisfied, and instructs the second determiner to determine whether a condition including a condition that the concentration of smoke is equal to or higher than the second determination value in addition to a condition that the amount of change relating to carbon monoxide is equal to or larger than the third determination value is satisfied.

5. The detector of claim 4, wherein
the preliminary determiner is configured to, when a state where the concentration of smoke is smaller than a predetermined threshold value continues for a second determination time period, proceed to a mode of selecting either the first determiner or the second determiner based on the result of determination of whether the switching condition is satisfied.

6. The detector of claim 5, wherein
the second determination time period is set to a time period longer than the first determination time period.

7. The detector of any one of claims 1 to 6, further comprising a third sensor configured to measure a temperature,
wherein the processing device is configured to determine whether the predetermined condition is satisfied with regard to the temperature measured by the third sensor.

8. A detection method comprising:

obtaining, from a sensing device, a concentration of smoke in air and a concentration of carbon monoxide in air;

determining, by a processing device, whether a predetermined condition is satisfied with regard to the obtained concentration of smoke and concentration of carbon monoxide;

outputting, from a notifying device, a notification signal when the predetermined condition is satisfied,

the method further comprising selecting, by the processing device, either a first condition or a second condition as the predetermined condition based on a result of determination of whether a switching condition for the concentration of smoke is satisfied, the first condition being for either the concentration of smoke or the concentration of carbon monoxide, and the second condition being for both the concentration of smoke and the concentration of carbon monoxide.

9. The detection method of claim 8, wherein
the switching condition is that an amount of change in the concentration of smoke within a predetermined reference time period is equal to or larger than a first determination value.

10. The detection method of claim 9, wherein:

the first condition includes a condition that the concentration of smoke is equal to or higher than a second determination value is satisfied, but does not include a condition for the concentration of carbon monoxide;

the second condition includes a condition that the concentration of smoke is equal to or higher than the second determination value in addition to a condition that an amount of change in the concentration of carbon monoxide within a predetermined reference time period is equal to or larger than a third determination value;

the processing device selects the first condition when the amount of change relating to smoke is smaller than the first determination value; and

the processing device selects the second condition when the amount of change relating to smoke is equal to or larger than the first determination value.

11. A detection system comprising:

the detector of any one of claims 1 to 7; and

a notifier configured to give notice according to the notification signal outputted from the notifying device.

12. A program for allowing one or more computers to function as the processing device and the notifying device of the detector of any one of claims 1 to 7.

Drawing