Combustion apparatus

Abstract

To provide a combustion apparatus capable of reducing wasteful drive of a blower fan in the case of a small effect of scavenging operation.SOLUTION: In a combustion apparatus 10 installed indoors, control means 16, assuming exhaust leakage from an exhaust passage 14 during combustion, estimates a concentration of indoor carbon monoxide on the basis of concentrations regularly detected and acquired by a CO sensor 15, makes the apparatus perform safe operation by stopping combustion when a detected concentration is a first concentration or more, makes a blower fan 12 perform scavenging operation by stopping combustion when a detected concentration is less than the first concentration and the estimated concentration of indoor carbon monoxide is a second concentration or more that is lower than the first concentration, makes scavenging operation continue when a detected concentration after a predetermined time has elapsed since the start of scavenging operation is less than the second concentration, and stops the blower fan 12 in the case of the second concentration or more.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] FIELD OF THEINVENTION This invention relates to safe operation of a combustion system, and more particularly to safe operation of a combustion system when an exhaust leak is suspected. [Background technology]

[0002] 2. Description of the Related Art Conventionally, combustion-type water heaters and heating appliances equipped with a combustion device have been widely used. Water heaters include indoor installation types, and heating appliances are generally installed in the room to be heated.

[0003] The combustion device of the equipment installed indoors introduces air for combustion, burns fuel, and generates combustion heat. This combustion heat is used by the water heater to heat water to provide hot water, and by the space heater to heat air or water to provide heating. The air for combustion introduced into the combustion device is indoor air or outdoor air introduced through an air supply passage extending from the outdoors to the combustion device.

[0004] The exhaust gas from a combustion device may contain high concentrations of carbon monoxide, which is harmful to humans, due to incomplete combustion. In order to prevent indoor air pollution by this exhaust gas, the exhaust gas after being used for heating is discharged through an exhaust passage extending from the combustion device to the outdoors. Normally, there is no exhaust gas leakage from the exhaust passage, so the carbon monoxide concentration in the room does not increase.

[0005] However, if a hole is created in the exhaust passage or if a misalignment occurs in the connection of the exhaust passage, the combustion exhaust gas will leak into the room. Therefore, as disclosed in Patent Document 1, for example, a technique is known in which the carbon monoxide concentration in the room is estimated based on the detected carbon monoxide concentration in the combustion exhaust gas under the assumption that the combustion exhaust gas has leaked into the room, and the carbon monoxide concentration in the room is prevented from exceeding a preset concentration. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-99424 A Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, in order to reduce the estimated indoor carbon monoxide concentration, purging (scavenging operation) is performed by a blower fan. However, in the case of a combustion device that uses indoor air for combustion, if exhaust gas actually leaks from the exhaust passage into the room, even if indoor air is introduced by scavenging operation, the exhaust gas leaks into the room, so the effect of reducing the indoor carbon monoxide concentration by scavenging operation is small.

[0008] In addition, in the case of a combustion device that uses outdoor air introduced from the intake passage for combustion, the air is sucked in from the outdoors to be scavenged, so the exhaust of indoor air is not promoted, and the scavenging operation has almost no effect on reducing the indoor carbon monoxide concentration. If there is a leak in either the exhaust passage or the intake passage, the indoor air is sucked in and leaks out into the room, just as in the case of using indoor air for combustion, so the effect of the scavenging operation is small.

[0009] Thus, in the technology of Patent Document 1, even when the effect of the scavenging operation in reducing the carbon monoxide concentration in the room is small, there is a waste of driving the blower fan to perform the scavenging operation. Therefore, the present invention aims to provide a combustion device that can reduce the waste of driving the blower fan when the effect of the scavenging operation is small. [Means for solving the problem]

[0010] The combustion device of the invention of claim 1 has a combustion section, a blower fan that supplies air to the combustion section, an exhaust passage for exhausting air from the combustion section to the outside, a CO sensor that detects a carbon monoxide concentration in the exhaust passage, and a control means for controlling combustion in the combustion section, and is installed indoors. The control means assumes that exhaust leaks from the exhaust passage during combustion in the combustion section, estimates the carbon monoxide concentration in the room based on the concentration detected by the CO sensor that is periodically acquired, and immediately stops combustion when the concentration detected by the CO sensor is equal to or higher than a preset first concentration. The apparatus is characterized in that it is configured to perform a safety operation, and when the concentration detected by the CO sensor is less than the first concentration and the estimated carbon monoxide concentration in the room becomes equal to or greater than a second concentration that is set in advance lower than the first concentration, it stops combustion and performs a scavenging operation by the blower fan, and when the concentration detected by the CO sensor when a predetermined time has elapsed since the start of the scavenging operation is less than the second concentration, it continues the scavenging operation, and when the concentration detected by the CO sensor when the predetermined time has elapsed since the start of the scavenging operation is equal to or greater than the second concentration, it stops the blower fan.

[0011] According to the above configuration, when the concentration detected by the CO sensor that detects the carbon monoxide concentration in the exhaust passage becomes equal to or greater than the first concentration during combustion in the combustion section, the combustion is immediately stopped to perform a safe operation. Also, even if the concentration detected by the CO sensor during combustion is less than the first concentration, when the estimated carbon monoxide concentration in the room becomes equal to or greater than the second concentration set lower than the first concentration, the combustion is stopped and a scavenging operation is performed by the blower fan. If the concentration detected by the CO sensor is equal to or greater than the second concentration after a predetermined time has elapsed since the start of the scavenging operation, that is, if the effect of the scavenging operation is small, the blower fan is stopped. Therefore, when the carbon monoxide concentration in the room rises above the second concentration, which is the judgment criterion, the combustion can be stopped to stop the increase, and wasteful driving of the blower fan can be reduced when the effect of the scavenging operation is small.

[0012] The combustion apparatus of the invention of claim 2 is characterized in that in the invention of claim 1, the control means performs the scavenging operation by the blower fan in the safety operation, and stops the blower fan when the predetermined time has elapsed from the start of the scavenging operation. According to the above configuration, since the occurrence of incomplete combustion is evident from the carbon monoxide concentration in the exhaust passage and there is a high probability that the combustion exhaust gas leaking from the exhaust passage is being introduced into the combustion device, a scavenging operation is performed for a predetermined time as a safety operation. After the exhaust passage is scavenged by this scavenging operation for the predetermined time, the blower fan is stopped. Therefore, it is possible to reduce the waste of driving the blower fan when the effect of the scavenging operation is small due to exhaust gas leakage with respect to reducing the carbon monoxide concentration in the room.

[0013] The combustion device of the invention of claim 3 is characterized in that in the invention of claim 1 or 2, the control means determines that an exhaust leak has occurred in a room in which the combustion device is installed when the blower fan is stopped when the predetermined time has elapsed from the start of the scavenging operation. According to the above configuration, when the effect of scavenging operation is small in reducing the carbon monoxide concentration in the room, it is determined that an exhaust leak has occurred and the operation of the blower fan is stopped. Therefore, by determining that an exhaust leak has occurred, it is possible to, for example, prohibit combustion to prevent the carbon monoxide concentration from increasing, and to, for example, prompt repair or inspection of the combustion device by notifying the user of the occurrence of an exhaust leak into the room. Effect of the Invention

[0014] According to the combustion apparatus of the present invention, it is possible to reduce wasteful driving of the blower fan when the effect of the scavenging operation is small. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a water heater equipped with a combustion device according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart showing estimation of an indoor carbon monoxide concentration periodically performed by the combustion device according to the embodiment of the present invention. [Diagram 3] 4 is a flowchart showing a determination of a carbon monoxide concentration that is periodically detected and estimated by the combustion device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the mode for carrying out the present invention will be described based on examples. EXAMPLES

[0017] As shown in Fig. 1, an indoor-installation type water heater 1 is installed in a room I, and a combustion device 10 mounted on this water heater 1 is also installed in the room I. The water heater 1 has a combustion device 10, a water supply section 3, a heat exchange section 4, and a hot water outlet section 5, and uses the combustion heat generated in the combustion device 10 to heat clean water supplied from the water supply section 3 in the heat exchange section 4, and supplies the heated hot water via the hot water outlet section 5 to, for example, a hot water tap 6.

[0018] The combustion device 10 includes a combustion section 11, a blower fan 12, a fuel supply section 13, an exhaust passage 14, a CO sensor 15, and a control means 16. The combustion section 11 has a plurality of combustion stages to adjust the generated combustion heat. The blower fan 12 supplies air from inside a room I to the combustion section 11 as air for combustion. The fuel supply section 13 supplies, for example, fuel gas as fuel to the combustion section 11. The combustion section 11 mixes and burns the fuel gas and the air for combustion to generate combustion heat. The combustion gas carrying this combustion heat flows toward the heat exchange section 4 by the drive of the blower fan 12, and the combustion gas (combustion exhaust) that has passed through the heat exchange section 4 is discharged to the outdoors O via the exhaust passage 14.

[0019] The exhaust passage 14 extends from the combustion section 11 to the outdoors O. A CO sensor 15 is disposed in the exhaust passage 14. The CO sensor 15 detects the carbon monoxide concentration of the fluid (air, combustion exhaust) flowing through the exhaust passage 14, i.e., the carbon monoxide concentration in the exhaust passage 14. The control means 16 controls the combustion in the combustion section 11 so as to generate the required amount of heat by adjusting the fuel supply flow rate of the fuel supply section 13, the air flow rate of the blower fan 12, and the number of combustion stages in the combustion section 11. For ventilation of the room I, for example, a ventilation port or window (not shown) is provided which connects the room I to the outdoors O.

[0020] In order to supply hot water at the set hot water supply temperature, the water heater 1 performs combustion in the combustion section 11 of the combustion device 10, and mixes clean water with the hot water heated in the heat exchange section 4 in the hot water outlet section 5. The set hot water supply temperature is set by operating an operation terminal 17 connected to the control means 16. The control means 16 is a computer that executes control programs for various operations to perform control, based on, for example, input information from the operation of the operation terminal 17, detection information from various sensors represented by the CO sensor 15, etc.

[0021] In the hot water supply operation of the water heater 1, the control means 16 calculates the required amount of heat based on, for example, the set hot water supply temperature, the flow rate detected by the water supply flow rate sensor 3a of the water supply unit 3, and the temperature detected by the water supply temperature sensor 3b. Then, in order to generate the calculated amount of heat, the control means 16 controls the air flow rate of the blower fan 12, the fuel supply flow rate of the fuel supply unit 13, and the number of combustion stages of the combustion unit 11. Furthermore, the control means 16 adjusts the mixture ratio of the hot water heated in the heat exchange unit 4 in the hot water outlet unit 5 and the clean water from the bypass passage 5a by adjusting the flow rate adjustment valve 5b of the bypass passage 5a branched off from the water supply unit 3 and connected to the hot water outlet unit 5, and supplies hot water adjusted to the set hot water supply temperature.

[0022] In order to prevent accidents caused by carbon monoxide, the control means 16 is configured to repeatedly estimate the carbon monoxide concentration in the room I at regular intervals while the combustion device 10 is in operation. This periodic estimation of the carbon monoxide concentration (CO concentration estimation) will be described with reference to the flowchart in Fig. 2. In the figure, Si (i = 1, 2, ...) represents a step.

[0023] First, in S1, the detected concentration (detected CO concentration) of the CO sensor 15 is obtained, and then in S2, the exhaust flow rate is obtained based on the fan rotation speed of the blower fan 12. Then, in S3, assuming that exhaust gas is leaking into room I, the carbon monoxide concentration (indoor CO concentration) in room I is estimated based on the detected CO concentration and exhaust flow rate that have been obtained, and the CO concentration estimation is terminated.

[0024] In S3, as in Patent Document 1, for example, the volume of room I and the ventilation rate at which the air in room I is ventilated are taken into consideration, and the previously estimated indoor CO concentration is estimated by reflecting fluctuations in the amount of carbon monoxide over a certain period. Even when the combustion device 10 is on standby, the previously estimated indoor CO concentration can be estimated by reflecting only fluctuations due to ventilation, since the exhaust flow rate is zero. Note that the carbon monoxide concentration in the atmosphere can usually be considered to be zero.

[0025] The combustion device 10 in operation introduces air from the room I, burns it in the combustion section 11, and discharges the combustion exhaust gas to the outdoor O through the exhaust passage 14. If the combustion is normal, the detected CO concentration will be low and the estimated indoor CO concentration will not increase. After the combustion is stopped, the blower fan 12 performs a scavenging operation for a preset predetermined time, and then the blower fan 12 is stopped and the device waits until the next combustion. The predetermined time is set so that the scavenging operation is performed to cool the device and prevent overheating of the heat exchange section 4, and the combustion exhaust gas remaining in the exhaust passage 14 is discharged to the outdoor O to prevent the combustion exhaust gas from flowing back into the room I. On the other hand, if the detected CO concentration increases, there is a high probability that an abnormality has occurred in the combustion (for example, incomplete combustion due to exhaust gas leaking into the room I).

[0026] Since high concentrations of carbon monoxide are harmful to the human body, the control means 16 compares the detected CO concentration obtained during the periodic CO concentration estimation and the estimated indoor CO concentration with respective preset criteria each time a CO concentration estimation is performed, and stops combustion if the detected CO concentration exceeds the criteria. In this carbon monoxide concentration judgment (CO concentration judgment), for example, as shown in Fig. 3, first in S11, it is judged whether the detected CO concentration is equal to or higher than a first concentration (e.g., 1200 ppm) preset as a judgment criterion.

[0027] If the determination in S11 is Yes, the process proceeds to S12, where the combustion in the combustion unit 11 is immediately stopped and the process proceeds to S13. At this time, the combustion in the combustion unit 11 is prohibited, and the operation terminal 17 issues a notification of the occurrence of an abnormality or a notification encouraging ventilation, for example, by voice and display.

[0028] Then, in S13, the blower fan 12 is driven to perform scavenging operation until a predetermined time has elapsed, and the combustion exhaust gas containing a high concentration of carbon monoxide remaining in the exhaust passage 14 is discharged to the outdoors O, and the process proceeds to S14. During the scavenging operation, the CO concentration is periodically estimated as during combustion, and the indoor CO concentration taking into account the ventilation rate is estimated based on the detected CO concentration and the exhaust flow rate. Then, when the predetermined time has elapsed, in S14, the blower fan 12 is stopped, and the process proceeds to S15.

[0029] In S15, it is determined from the increase in the detected CO concentration that an exhaust leak has occurred in the room I where the combustion device 10 is installed, and the operation terminal 17 notifies the user of the exhaust leak into the room I, for example by voice and display, and the CO concentration determination ends. The exhaust leak may be notified when the combustion is stopped in S12. Since the exhaust flow rate is zero after the blower fan 12 is stopped, the CO concentration in the room I can be estimated periodically by reflecting fluctuations due to ventilation.

[0030] On the other hand, if the determination in S11 is No, the process proceeds to S16, where it is determined whether the indoor CO concentration estimated by the CO concentration estimation is equal to or higher than a second concentration preset as a determination criterion. The second concentration is set lower than the first concentration, and is set, for example, to a carbon monoxide concentration (300 ppm) in room I at which combustion stop is required in the JIS standard.

[0031] If the estimated indoor CO concentration is less than the second concentration and therefore the determination in S16 is No, the CO concentration determination is terminated without stopping the combustion. Since the detected CO concentration and the indoor CO concentration are lower than their respective determination standards, the combustion is in a normal state and the combustion continues.

[0032] On the other hand, if the estimated indoor CO concentration is equal to or higher than the second concentration and therefore the determination in S16 is Yes, the process proceeds to S17, where combustion in the combustion unit 11 is stopped to stop the increase in the indoor CO concentration, and the process proceeds to S18. At this time, combustion in the combustion unit 11 is prohibited, and an error notification or a notification encouraging ventilation is issued on the operation terminal 17, for example, by voice and display.

[0033] Next, in S18, scavenging operation is performed by the blower fan 12 until a predetermined time has elapsed, and the process proceeds to S19. During scavenging operation, CO concentration estimation is performed in the same manner as during combustion. Then, in S19, it is determined whether the detected CO concentration when a predetermined time has elapsed since the start of scavenging operation is equal to or higher than the second concentration. The scavenging operation causes the air in the room I to be exhausted to the outside O via the exhaust passage 14, promoting ventilation, and the detected CO concentration of the CO sensor 15 that detects the carbon monoxide concentration of the air in the room I should be lower than the second concentration.

[0034] However, if an exhaust gas leak occurs from the exhaust passage 14 into the room I, the air that should be discharged by the scavenging operation leaks into the room I, so ventilation is not promoted and the effect of the scavenging operation is reduced. Therefore, if the determination in S19 is Yes, the process proceeds to S20, where the blower fan 12 is stopped and the process proceeds to S21. Then, in S21, it is determined that an exhaust gas leak occurs in the room I where the combustion device 10 is installed, and the operation terminal 17 notifies the exhaust gas leak into the room I, for example, by voice and display, and the CO concentration determination is terminated. If it is determined in S19 that the effect of the scavenging operation is small, the scavenging operation is stopped because the drive of the blower fan 12 is wasteful. Since the exhaust gas flow rate is zero after the blower fan 12 is stopped, the CO concentration in the room I can be estimated periodically by reflecting the fluctuation due to ventilation.

[0035] On the other hand, if the determination in S19 is No, the process proceeds to S22, where the scavenging operation is continued and the process proceeds to S23. For example, even if there is no exhaust leakage, a part of the combustion exhaust gas discharged to the outside O may be blown into the room I by the wind, causing the detected CO concentration to increase and the estimated indoor CO concentration to increase. In this case, the detected CO concentration decreases due to the scavenging operation for a predetermined time, and it is found in S19 that the scavenging operation is sufficiently effective, so that the scavenging operation can be continued even after the scavenging operation for the predetermined time to quickly decrease the carbon monoxide concentration in the room I. Also, even if there is no exhaust leakage, for example, in a case where wind blows into the exhaust passage 14 and the combustion exhaust gas cannot be discharged smoothly, causing the detected CO concentration to increase and the estimated indoor CO concentration to increase, the detected CO concentration decreases due to the scavenging operation for a predetermined time, so that the scavenging operation is continued.

[0036] Next, in S23, it is determined whether the estimated indoor CO concentration is less than a third concentration (e.g., 100 ppm) that is set in advance as a determination criterion lower than the second concentration. Since it has been found that the scavenging operation is sufficiently effective in reducing the carbon monoxide concentration in the room I, the CO concentration estimation when the scavenging operation is continued may be simplified by setting the detected CO concentration to a fixed value (e.g., 0 ppm) instead of the actual concentration detected by the CO sensor 15. If the determination in S23 is No, the process returns to S22 to continue the scavenging operation. If the determination in S23 is Yes, the process proceeds to S24, where the blower fan 12 is stopped and the CO concentration determination is terminated. Since the exhaust flow rate is zero after the blower fan 12 is stopped, the CO concentration in the room I can be estimated periodically by reflecting fluctuations due to ventilation.

[0037] In this way, if an exhaust gas leak occurs from the exhaust passage 14 into the room I in which the combustion device 10 is installed, the air in the room I mixed with the combustion exhaust gas is supplied to the combustion section 11, causing incomplete combustion and increasing the CO concentration detected by the CO sensor 15. If the detected CO concentration is equal to or higher than the first concentration, the control means 16 immediately stops the combustion and performs a scavenging operation for a predetermined time as a safety operation. Also, if the detected CO concentration is less than the first concentration but the estimated indoor CO concentration is equal to or higher than the second concentration, the control means 16 stops the combustion and performs a scavenging operation for a predetermined time.

[0038] If there is an exhaust leak from the exhaust passage 14 into the room I, the air in the room I that should be exhausted to the outside O by the scavenging operation leaks from the exhaust passage 14 into the room I. Therefore, the effect of the scavenging operation on reducing the carbon monoxide concentration in the room I is small, so the blower fan 12 is stopped after performing the scavenging operation for a predetermined time. On the other hand, there are cases where the estimated indoor CO concentration rises even if there is no exhaust leak into the room I. In this case, the effect of the scavenging operation is sufficient, so the scavenging operation is continued until the estimated indoor CO concentration falls below the third concentration, and the carbon monoxide concentration in the room I is quickly reduced.

[0039] The operation and effects of the above-mentioned combustion device 10 will now be described. When the CO concentration detected by the CO sensor 15 during combustion in the combustion section 11 becomes equal to or greater than the first concentration, the control means 16 immediately stops the combustion to perform a safe operation. Also, even if the CO concentration detected by the CO sensor 15 during combustion in the combustion section 11 is less than the first concentration, when the estimated indoor CO concentration becomes equal to or greater than the second concentration set lower than the first concentration, the control means 16 stops the combustion and performs a scavenging operation by the blower fan 12. When the CO concentration detected by the CO sensor 15 after a predetermined time has elapsed since the start of the scavenging operation is equal to or greater than the second concentration, that is, when the effect of the scavenging operation is small, the blower fan 12 is stopped. Therefore, when the carbon monoxide concentration in the room I rises above the second concentration, which is the judgment criterion, the combustion can be stopped to stop this increase, and wasteful driving of the blower fan 12 can be reduced when the effect of the scavenging operation is small with respect to the decrease in the carbon monoxide concentration in the room I.

[0040] In the safety operation, the control means 16 performs a scavenging operation by the blower fan 12, and stops the blower fan 12 when a preset predetermined time has elapsed since the start of the scavenging operation. Since the occurrence of incomplete combustion is evident from the carbon monoxide concentration in the exhaust passage 14, and it is highly likely that the combustion device 10 is burning while introducing the combustion exhaust gas leaked from the exhaust passage 14, the control means 16 performs a scavenging operation for a predetermined time as a safety operation. After scavenging the exhaust passage 14 by the scavenging operation for the predetermined time, the control means 16 stops the blower fan 12. Therefore, it is possible to reduce the waste of driving the blower fan 12 when the effect of the scavenging operation on reducing the carbon monoxide concentration in the room I is small due to the leakage of the combustion exhaust gas.

[0041] The control means 16 determines that an exhaust leak has occurred in the room I when the blower fan 12 is stopped when a predetermined time has elapsed since the start of the scavenging operation. In other words, when the effect of the scavenging operation is small with respect to the reduction in the carbon monoxide concentration in the room I, it determines that an exhaust leak has occurred and stops the blower fan 12. Therefore, by determining that an exhaust leak has occurred, it is possible to, for example, prohibit combustion in the combustion section 11 to prevent the carbon monoxide concentration from increasing, and, for example, to prompt repair or inspection of the combustion device 10 by notifying the occurrence of an exhaust leak into the room I.

[0042] The combustion device 10 may be mounted on a heating device, and in this case too, the carbon monoxide concentration is periodically determined to monitor exhaust leakage, thereby reducing the waste of driving the blower fan 12 during scavenging operation. Also, in a forced supply and exhaust type (FF type) combustion device that supplies air from outdoors and exhausts it outdoors, the detected and estimated carbon monoxide concentration is determined to monitor exhaust leakage, preventing an increase in the carbon monoxide concentration and reducing the waste of driving the blower fan during scavenging operation. In addition, a person skilled in the art can implement the present invention in various modified forms without departing from the spirit of the present invention, and the present invention includes such modified forms. [Explanation of symbols]

[0043] 1: Water heater 3: Water supply section 4:Heat exchange section 5: Tap area 10: Combustion equipment 11: Combustion section 12: Blower fan 13:Fuel supply section 14: Exhaust passage 15: CO sensor 16: Control means 17: Operation terminal

Claims

1. A combustion device that is installed indoors and has a combustion section, a blower fan that supplies air to the combustion section, an exhaust passage for exhausting air from the combustion section to the outdoors, a CO sensor that detects a carbon monoxide concentration in the exhaust passage, and a control means that controls combustion in the combustion section, the control means assumes that exhaust gas leaks from the exhaust passage during combustion in the combustion section, and estimates a carbon monoxide concentration in the room based on a detected concentration of the CO sensor that is periodically acquired; When the concentration detected by the CO sensor is equal to or higher than a first concentration set in advance, the combustion is immediately stopped to perform a safety operation. When the detected concentration of the CO sensor is less than the first concentration and the estimated carbon monoxide concentration in the room is equal to or greater than a second concentration that is set in advance lower than the first concentration, combustion is stopped and a scavenging operation is performed by the blower fan. the combustion device is configured to continue the scavenging operation if the concentration detected by the CO sensor when a preset predetermined time has elapsed since the start of the scavenging operation is less than the second concentration, and to stop the blower fan if the concentration detected by the CO sensor when the preset time has elapsed since the start of the scavenging operation is equal to or greater than the second concentration.

2. 2. The combustion apparatus according to claim 1, wherein the control means, in the safety operation, performs the scavenging operation by using the blower fan, and stops the blower fan when the predetermined time has elapsed from the start of the scavenging operation.

3. The combustion apparatus according to claim 1 or 2, characterized in that the control means determines that an exhaust leak has occurred in a room in which the combustion apparatus is installed when the blower fan is stopped when the predetermined time has elapsed from the start of the scavenging operation.

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