Fire detection method and fire detection system

Abstract

To provide a fire detection method and a fire detection system that suppress false recognition caused by sunlight.SOLUTION: A fire detection method for identifying a fire source position within a fire monitoring range from detection results of a plurality of detection devices installed to detect a fire source position within each pre-assigned range of the fire monitoring range, includes: a first step of installing the plurality of detection devices to cover the fire monitoring ranges within the assigned range of at least two of the plurality of detection devices; and a second step of specifying data on the fire source position corresponding to the same position as a fire source position in the fire monitoring range when the data on the fire source position corresponding to the same position is acquired from at least two detection devices among the plurality of detection devices as the detected result.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a fire detection method and a fire detection system for identifying the location of a fire source within a fire monitoring range.

Background Art

[0002] In a large-scale space, there is a system that arranges fire detection devices for each compartment and calculates the location of the fire source (see, for example, Patent Document 1). In the fire detection system according to Patent Document 1, a plurality of exploration devices are arranged within the fire monitoring range, and a configuration is provided in which the fire source position data specified by the exploration device located closest to the same fire source position is adopted.

[0003] By having such a configuration, in the fire detection system according to Patent Document 1, it is possible to suppress deterioration in the calculation accuracy of the fire source position and to suppress an increase in the calculation time of the fire source position.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As an example of a large-scale space where fire monitoring should be performed, a dome stadium can be mentioned. In a dome stadium, natural turf may be used. In such a case, in order to grow natural turf, a configuration may be adopted in which the ceiling is opened and closed to allow sunlight to enter.

[0006] When conducting fire monitoring with the ceiling open, there is a risk of misidentifying the reflected light of sunlight as a fire. If a fire misidentification occurs, it may not only result in an alarm operation to notify of the fire but also involve a water discharge operation for fire extinguishing. Therefore, in order to improve the reliability of the fire detection system, it is important to suppress the misidentification of fires caused by sunlight and prevent unnecessary alarm operations or water discharge operations.

[0007] Note that suppressing misidentification of fires is a common issue not only in dome stadiums but also in various fire monitoring areas. Therefore, a fire detection system that suppresses misidentification caused by sunlight is strongly desired in fire monitoring areas affected by the reflected light of sunlight.

[0008] This disclosure was made to solve the above problems and aims to obtain a fire detection method and a fire detection system capable of suppressing misidentification of fires caused by sunlight.

Means for Solving the Problems

[0009] The fire detection method according to this disclosure is a fire detection method for identifying the position of a fire source within a fire monitoring area from the respective detection results of a plurality of detection devices installed to detect the position of the fire source within each of the pre-assigned respective responsible areas within the fire monitoring area, comprising: a first step of installing a plurality of detection devices such that the fire monitoring area is covered by the responsible areas of at least two of the plurality of detection devices; and a second step of, when position data of a fire source corresponding to the same position is obtained as a detection result from at least two of the plurality of detection devices, identifying the position data of the fire source corresponding to the same position as the position of the fire source within the fire monitoring area. In addition, the fire detection system according to the present disclosure includes a plurality of detection devices installed to detect the position of a fire source within each of the pre-assigned responsible areas in the fire monitoring range, and a general controller that identifies the position of the fire source within the fire monitoring range from the respective detection results of the plurality of detection devices. Each of the plurality of detection devices identifies the position of the fire source within the responsible area based on the detection information including the temperature information and the fire source position information acquired within the responsible area, and when the position of the fire source can be identified, executes a detection process of outputting the position data of the identified fire source as a detection result. The fire monitoring range is covered by the responsible areas of at least two of the plurality of detection devices, and when the general controller acquires the position data of the fire source corresponding to the same position as a detection result from at least two of the plurality of detection devices, the general controller identifies the position data of the fire source corresponding to the same position as the position of the fire source within the fire monitoring range.

Advantages of the Invention

[0010] According to the present disclosure, a fire detection method and a fire detection system capable of suppressing misrecognition of a fire caused by sunlight can be obtained.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the fire detection method and the fire detection system of the present disclosure will be described with reference to the drawings. The fire detection method and the fire detection system according to the present disclosure are characterized in that when the same fire source position is specified by two or more detection devices, it is determined that a fire has occurred, thereby suppressing misrecognition of a fire caused by sunlight.

[0013] Embodiment 1. FIG. 1 is an overall configuration diagram of a fire detection system according to Embodiment 1 of the present disclosure. The fire detection system shown in FIG. 1 includes a plurality of detection devices 10(1) to 10(N) (N is an integer of 2 or more) and a general controller 20.

[0014] The N detection devices 10(1) to 10(N) are arranged to detect the fire source position within their respective assigned ranges in the fire monitoring range. The general controller 20 has a function of specifying the fire source position within the fire monitoring range from the respective detection results obtained by the plurality of detection devices 10(1) to 10(N).

[0015] Each of the N exploration devices 10(1) to 10(N) has the same configuration. Therefore, when explaining the common configuration, hereinafter, it will be referred to as the exploration device 10. The exploration device 10 includes an individual controller 11, an infrared camera 12, and a drive mechanism 13 for moving the imaging area by the infrared camera 12 and changing the imaging position.

[0016] Note that the fire exploration system according to the present disclosure is characterized in that when the same fire source position is specified in two or more exploration devices 10, it is determined that a fire has occurred, thereby suppressing misrecognition of a fire caused by sunlight. Therefore, each position within the fire monitoring range is covered by the responsible ranges of at least two of the plurality of exploration devices 10(1) to 10(N).

[0017] The infrared camera 12 has a function of acquiring detection information including temperature information and fire source position information corresponding to each of a plurality of pixels by imaging the responsible range. Further, the individual controller 11 executes a specific process for specifying the fire source position within the responsible range based on the detection information acquired by the infrared camera 12. Furthermore, when the fire source position can be specified by the specific process, the individual controller 11 outputs the position data of the specified fire source to the overall controller 20. Note that the drive mechanism 13 will be described later.

[0018] The overall controller 20 specifies the fire source position based on the position data received from each of the individual controllers 11 in each exploration device 10.

[0019] Next, a specific example of the monitoring area accompanying the movement of the infrared camera 12 using the viewing angle of the infrared camera 12 and the drive mechanism 13 will be described with reference to FIG. 2. FIG. 2 is an explanatory diagram regarding the instantaneous monitoring range AV in the vertical direction and the instantaneous monitoring range AH in the horizontal direction of the infrared camera 12 according to Embodiment 1 of the present disclosure.

[0020] Here, the vertical instantaneous monitoring range AV refers to the field of view in the vertical direction when the infrared camera 12 is fixed, that is, it corresponds to the vertical field of view angle. In the specific example in the upper part of FIG. 2, the case where the vertical field of view angle is 37.0 degrees is illustrated.

[0021] Also, the horizontal instantaneous monitoring range AH refers to the field of view in the horizontal direction when the infrared camera 12 is fixed, that is, it corresponds to the horizontal field of view angle. In the specific example in the lower part of FIG. 2, the case where the horizontal field of view angle is 50.0 degrees is illustrated.

[0022] By positioning the infrared camera 12 having such an instantaneous field of view angle of horizontal field of view angle 50.0 degrees × vertical field of view angle 37.0 degrees at a total of 12 positions as follows by the pan-tilt of the drive mechanism 13 and performing fire detection, fire monitoring in a wide monitoring area can be realized with one unit.

[0023] (1) Fix the pan-tilt pitch angle at -19.5 degrees from the horizontal and horizontally rotate to search for the fire source at 4 positions. (2) Next, fix the pan-tilt pitch angle at -47.5° from the horizontal and horizontally rotate to search for the fire source at 4 positions. (3) Next, fix the pan-tilt pitch angle at -75.5° from the horizontal and horizontally rotate to search for the fire source at 4 positions.

[0024] Next, the case where the infrared camera 12 misidentifies the fire source position due to the reflected light of sunlight will be described with reference to FIG. 3. FIG. 3 is an explanatory diagram comparing the case of detecting the fire source 1 with two infrared cameras 12(1) and 12(2) and the case of detecting the reflected lights 2(1) and 2(2) of sunlight as false alarm sources, that is, non-fire alarms, with two infrared cameras 12(1) and 12(2) in Embodiment 1 of the present disclosure.

[0025] More specifically, FIG. 3(A) illustrates a state in which one heat source 1 is detected by two infrared cameras 12(1) and 12(2). On the other hand, FIG. 3(B) illustrates a case in which the reflected light 2(1) of sunlight is detected as a false alarm factor by the first infrared camera 12(1), and the reflected light 2(2) of sunlight is detected as a false alarm factor by the second infrared camera 12(2). When the reflected light of sunlight enters the infrared camera 12, in some cases, the detection result may be about 500 degrees.

[0026] As shown in FIG. 3(A), when one heat source 1 occurs within the fire monitoring range, the position data 4a(Xa, Ya) of the heat source position 4a is detected by the first infrared camera 12(1), and the position data 4b(Xb, Yb) of the heat source position 4b is detected by the second infrared camera 12(2).

[0027] Here, the position data 4a(Xa, Ya) and the position data 4b(Xb, Yb) are the results of detecting one heat source 1 at the same position, and the distance between the position data 4a(Xa, Ya) and the position data 4b(Xb, Yb) is position data in the vicinity that falls within a preset allowable range. In the present disclosure, position data in the vicinity where the distance between two points falls within the allowable range will be referred to as position data of the "same position".

[0028] The allowable range of the distance between two points is determined from the detection accuracy of the heat source position. For example, if the detection accuracy is 2 m, it is set to 10 m, which is five times that. Alternatively, it can be determined from the water discharge accuracy of the water discharge operation after the heat source is detected, or from both the detection accuracy of the heat source position and the water discharge accuracy.

[0029] On the one hand, when affected by the reflected light 2 of sunlight within the fire monitoring range, usually, it is conceivable that the reflected light 2 will only be detected by one infrared camera 12. Also, when both of the two infrared cameras 12(1) and 12(2) are affected by the reflected light 2 of sunlight, as shown in Fig. 3(B), the reflected light 2(1) of sunlight reflected by the reflector 3(1) is detected as position data 5a(Xa, Ya) by the first infrared camera 12(1), and the reflected light 2(2) of sunlight reflected by the reflector 3(2) is detected as position data 5b(Xb, Yb) by the second infrared camera 12(2).

[0030] That is, it is rare to detect the reflected light 2 of sunlight with two infrared cameras 12(1) and 12(2). Even if detected with two infrared cameras 12(1) and 12(2), due to different reflectors 3(1) and 3(2), the position data 5a(Xa, Ya) and the position data 5b(Xb, Yb) will be detected as data outside the allowable range instead of neighboring position data within the allowable range.

[0031] Examples of the reflector 3 include smartphones, metal handrails, and metal gates used in events.

[0032] Therefore, the overall controller 20 can suppress the misrecognition of a fire caused by sunlight and detect the fire source 1 to be originally detected with high precision by executing the specific processing of the fire source position in the following steps.

[0033] Step S1: When the overall controller 20 obtains the position data of the fire source from any one of the plurality of exploration devices 10, it specifies the obtained position data of the fire source as the temporary fire source position. Here, for the sake of simplicity, the case where the position data of the fire source is obtained from the exploration device 10(1) is taken as an example for explanation.

[0034] Step S2: The overall controller 20 identifies other exploration devices among the remaining exploration devices 10(2) to 10(N) other than the one exploration device 10(1) that is the source of the transmitted fire source position data, for which the provisional fire source position is included in the responsible range. Here, for the sake of simplicity of explanation, a case where the fire source position data identified by the exploration device 10(1) is included in the exploration range of the exploration device 10(2) will be described as an example. That is, the exploration device 10(2) will be described as the identified other exploration device as follows.

[0035] Step S3: When the overall controller 20 acquires the fire source position data corresponding to the same position as the provisional fire source position from the individual controller 11 corresponding to the exploration device 10(2) identified as the other exploration device, the provisional fire source position is identified as the fire source position within the fire monitoring range.

[0036] Step S4: On the other hand, when the overall controller 20 cannot acquire the position data from the individual controller 11 corresponding to the exploration device 10(2) identified as the other exploration device, or even if the position data is acquired, but it is not the position data corresponding to the same position as the provisional fire source position, it is determined that it is affected by the false alarm factor, and the provisional fire source position is not identified as the fire source position within the fire monitoring range.

[0037] By executing such a series of identification processes in Steps S1 to S4, when the overall controller 20 identifies the same fire source position in two or more exploration devices 10, it can be determined that a fire has occurred at the same fire source position, and misrecognition of a fire caused by sunlight can be suppressed. As a result, unnecessary alarm operations or unnecessary water discharge operations can be suppressed, and the reliability of the fire exploration system can be improved.

[0038] In the above-described specific example, after obtaining the position data of the fire source from the exploration device 10(1) as the provisional fire source position, the exploration device 10(2) is specified as another exploration device, and when obtaining the position data of the fire source regarding the same position as the provisional fire source position from the exploration device 10(2), a method of specifying the provisional fire source position as the fire source position within the fire monitoring range was described. However, the method of specifying the fire source position according to the present disclosure is not limited to this.

[0039] As another method, without specifying another exploration device 10(2), when obtaining the position data of the fire source corresponding to the same fire source position from two or more exploration devices within a certain period of time, the same fire source position can also be specified as the fire source position within the fire monitoring range.

[0040] Embodiment 2. In this Embodiment 2, a specific method for performing fire monitoring of the ground of a dome stadium using three infrared cameras 12(1) to 12(3) will be described in detail with reference to FIGS. 4 to 6.

[0041] FIG. 4 is a top view for explaining the arrangement and monitoring range of three infrared cameras 12(1) to 12(3) in the fire exploration system according to Embodiment 2 of the present disclosure. When the ground 100 of a dome stadium is the object of fire monitoring, the three infrared cameras 12(1) to 12(3) are arranged as follows, for example, as shown in FIG. 4.

[0042] The first infrared camera 12(1) is installed on the third base side and performs fire exploration of the ground 100 over the assigned range Z(1). The second infrared camera 12(2) is installed on the first base side and performs fire exploration of the ground 100 over the assigned range Z(2). Further, the third infrared camera 12(3) is installed on the center side and performs fire exploration of the ground 100 over the assigned range Z(3).

[0043] The three infrared cameras 12(1) to 12(3) in each of the three exploration devices 10(1) to 10(3) are installed in their respective drive mechanisms 13, although not shown in the figure, and are position-controlled by their respective individual controllers 11 so that they can monitor the desired instantaneous monitoring ranges in the horizontal direction and the instantaneous monitoring ranges in the vertical direction.

[0044] For example, as described in the previous Embodiment 1, each of the three infrared cameras 12(1) to 12(3) is moved to 4 positions at each of the three elevation angles and position-controlled at a total of 12 positions, so that their respective assigned ranges Z(1) to Z(3) can be covered.

[0045] Here, the entire surface of the ground 100 is covered by any of the assigned ranges Z1(1) to Z(3) of the three infrared cameras 12(1) to 12(3). Also, inside the first-base side bench 101 is covered by the assigned range Z(1) of the first infrared camera 12(1) and the assigned range Z(3) of the third infrared camera 12(3), and inside the third-base side bench 102 is covered by the assigned range Z(2) of the second infrared camera 12(2) and the assigned range Z(3) of the third infrared camera 12(3).

[0046] In other words, when the entire surface of the ground 100, the inside of the first-base side bench 101, and the inside of the third-base side bench 101 are taken as the fire monitoring range, all positions within the fire monitoring range are covered by the assigned ranges of at least two of the three exploration devices 10(1) to 10(3).

[0047] Each of the three exploration devices 10(1) to 10(3) has the following three modes when conducting fire exploration. <Mode 1: Normal Exploration> In the normal exploration of Mode 1, while the infrared camera 12 is sequentially position-controlled to the desired positions, fire exploration of the assigned range Z is executed.

[0048] <Mode 2: Fixed-Point Exploration> In the fixed-point search of Mode 2, the infrared camera 12 is stopped at a desired position, and a partial fire search within the assigned scope Z is continuously executed. As an example, the first infrared camera 12(1) shown in FIG. 4 is position-controlled by fixed-point search so that the entire first-base bench 101 is included within the viewing angle, and then can continuously execute a fire search within the first-base bench 101 without moving.

[0049] Similarly, the second infrared camera 12(2) shown in FIG. 4 is position-controlled by fixed-point search so that the entire third-base bench 102 is included within the viewing angle, and then can continuously execute a fire search within the third-base bench 102 without moving.

[0050] <Mode 3: Rest> In the rest of Mode 3, the exploration device 10 is put into rest, and the exploration process using the infrared camera 12 is stopped. Thereby, the individual controller 11, the infrared camera 12, and the drive mechanism 13 can be put into rest, extending the device life and achieving energy conservation.

[0051] A specific example of the monitoring process combining these three modes will be described with reference to FIGS. 5 and 6. FIG. 5 is a top view for explaining the monitoring range in a fire exploration system according to Embodiment 2 of the present disclosure, where the first infrared camera 12(1) executes normal exploration, the second infrared camera 12(2) executes fixed-point search, and the third infrared camera 12(3) is in a rest state.

[0052] In FIG. 5, the first infrared camera 12(1) sequentially monitors the entire assigned scope Z(1) by executing normal exploration. When the overall controller 20 acquires the position data of the fire source from the individual controller 11 within the first exploration device 10(1), it determines whether the position data is within the ground 100 or within the first-base bench 101 of the scope Z(1) assigned to the first infrared camera 12(1), and specifies it as a tentative fire source position.

[0053] And, when the specified temporary fire source position is within the ground 100, since the ground 100 is included in both the responsible range Z(2) and the responsible range Z(3), the second exploration device 10(2) or the third exploration device Z(3) is specified as another exploration device 10.

[0054] On the other hand, when the specified temporary fire source position is within the first base side bench 101, since the inside of the first base side bench 101 is included only in the responsible range Z(3), the third exploration device Z(3) is specified as another exploration device 10.

[0055] Furthermore, the overall controller 20 outputs an exploration command for causing the individual controller 11 in the specified other exploration device 10 to perform a fire exploration at the temporary fire source position.

[0056] The individual controller 11 in the other exploration device 10 that has received the exploration command moves the infrared camera 12 to a position including the temporary fire source position and performs a fire exploration. Then, when a fire source is detected by the infrared camera 12, the individual controller 11 returns the position data of the fire source to the overall controller 20.

[0057] When the overall controller 20 determines that the position data of the fire source received from the other exploration device 10 as a response to the exploration command corresponds to the same position as the temporary fire source position, the overall controller 20 specifies the temporary fire source position as the fire source position within the fire monitoring range.

[0058] On the other hand, when the overall controller 20 cannot receive the position data of the fire source from the other exploration device 10 as a response to the exploration command, the overall controller 20 determines that the temporary fire source position is a false alarm. Also, even when the overall controller 20 can receive the position data of the fire source from the other exploration device 10 as a response to the exploration command, if the overall controller 20 determines that the received position data of the fire source is not the same position as the temporary fire source position, the overall controller 20 also determines that the temporary fire source position is a false alarm.

[0059] Also, in FIG. 5, when the overall controller 20 acquires the position data of the fire source from the individual controller 11 in the second exploration device 10(2) that is performing fixed-point exploration, if the position data is within the ground 100 or within the third-base side bench 102 among the areas being explored by the fixed-point exploration, it determines whether it is within the ground 100 or within the third-base side bench 102 and specifies it as the provisional fire source position.

[0060] Then, when the provisional fire source position specified by the overall controller 20 is within the ground 100, since the ground 100 is included in both the responsible range Z(1) and the responsible range Z(3), it specifies the first exploration device 10(2) or the third exploration device Z(3) as the other exploration device 10.

[0061] On the other hand, when the provisional fire source position specified by the overall controller 20 is within the third-base side bench 102, since the inside of the third-base side bench 102 is included only in the responsible range Z(3), it specifies the third exploration device Z(3) as the other exploration device 10.

[0062] Furthermore, the overall controller 20 outputs an exploration command to the individual controller 11 in the specified other exploration device 10 to perform a fire exploration at the provisional fire source position.

[0063] The individual controller 11 in the other exploration device 10 that has received the exploration command moves the infrared camera 12 to the position including the provisional fire source position and performs a fire exploration. Then, when a fire source is detected by the infrared camera 12, the individual controller 11 returns it to the overall controller 20 as the position data of the fire source.

[0064] When the overall controller 20 determines that the position data of the fire source received from the other exploration device 10 as a response to the exploration command corresponds to the same position as the provisional fire source position, it specifies the provisional fire source position as the fire source position within the fire monitoring range.

[0065] On the other hand, when the overall controller 20 cannot receive the fire source position data from another exploration device 10 as a response to the exploration command, it determines that the provisional fire source position is a false alarm. Further, even when the overall controller 20 can receive the fire source position data from another exploration device 10 as a response to the exploration command, if it determines that the received fire source position data is not at the same position as the provisional fire source position, it determines that the provisional fire source position is a false alarm.

[0066] FIG. 6 is a top view for explaining a monitoring range in a fire exploration system according to Embodiment 2 of the present disclosure, in which fixed-point exploration is performed by the first infrared camera 12(1), normal exploration is performed by the second infrared camera 12(2), and the third infrared camera 12(3) is in a standby state.

[0067] In the previous FIG. 5, normal exploration was performed by the first infrared camera 12(1), and the second infrared camera 12(2) performed fixed-point exploration on the third-base side bench 102. In contrast, in FIG. 6, normal exploration is performed by the second infrared camera 12(2), and the first infrared camera 12(1) performs fixed-point exploration on the first-base side bench 101, which is different.

[0068] That is, the roles of the first infrared camera 12(1) and the second infrared camera 12(2) are only different, and the basic operations regarding the identification of the fire source position are the same. Therefore, the detailed operation description regarding FIG. 6 is omitted.

[0069] The overall controller 20 can operate the fire exploration system by alternately executing the exploration operations shown in FIG. 5 and the exploration operations shown in FIG. 6 at regular intervals. By performing such an operation, compared with the case where normal exploration is always performed by all three exploration devices 10(1) to 10(3), energy saving can be achieved, the device life can be extended with a decrease in the operating rate, and a fire exploration system that can suppress misrecognition of fires caused by sunlight can be realized.

[0070] Note that the third infrared camera 12(3) may similarly be used to perform normal exploration, while the first infrared camera 12(1) and the second infrared camera 12(2) are put on standby. In this case as well, since the basic operations for identifying the fire source location are the same, detailed operation descriptions are omitted.

Explanation of Signs

[0071] 1 Fire source, 2 Reflected light, 3 Reflective material, 4a, 4b, 5a, 5b Position data, 10 Exploration device, 11 Individual controller, 12 Infrared camera, 13 Drive mechanism, 20 Overall controller.

Claims

1. A fire detection method for identifying the position of a fire source within a fire monitoring range from the respective detection results of a plurality of detection devices installed to search for the position of a fire source within each of the pre-assigned respective areas of responsibility within the fire monitoring range, comprising: A first step of installing the plurality of detection devices such that the fire monitoring range is covered by the areas of responsibility of at least two of the plurality of detection devices; A second step of identifying, as the position of the fire source within the fire monitoring range, the position data of the fire source corresponding to the same position when the position data of the fire source corresponding to the same position is obtained as the detection result from at least two of the plurality of detection devices; A fire detection method having the above.

2. A fire detection system comprising a plurality of detection devices installed to search for the position of a fire source within each of the pre-assigned respective areas of responsibility within a fire monitoring range, and A central controller for identifying the position of a fire source within the fire monitoring range from the respective detection results of the plurality of detection devices, wherein: Each of the plurality of detection devices identifies the position of a fire source within the area of responsibility based on detection information including temperature information and fire source position information obtained within the area of responsibility, and when the position of the fire source can be identified, executes a detection process of outputting the position data of the identified fire source as the detection result; The fire monitoring range is covered by the areas of responsibility of at least two of the plurality of detection devices; When the central controller obtains the position data of a fire source corresponding to the same position as the detection result from at least two of the plurality of detection devices, the central controller identifies the position data of the fire source corresponding to the same position as the position of the fire source within the fire monitoring range; A fire detection system.

3. Each of the plurality of detection devices has, as a mode for executing the detection process: Mode 1 for performing normal detection by executing fire detection within the assigned area of responsibility; Mode 2 for performing fixed-point detection by continuously executing fire detection on a part of the area of responsibility; Mode 3 for suspending the detection process; and the three modes are switchable; The central controller controls so that the normal detection in Mode 1 is not always executed by all of the plurality of detection devices. The fire detection system according to Claim 2.

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