JPH0684077A - Fire detection method - Google Patents

Abstract

PURPOSE:To clearly distinguish fire from non-fire by calculating the temperature of a body to be detected based upon the relative ratio of intensity values of plural infrared-ray radiation bands including the intensity of infrared rays existing at least in the resonance radiation area of CO2. CONSTITUTION:Infrared rays radiated from a fire source or a similar heating source are periodically divided by a chopper and four respectively different wavelength bands are detected by four pyroelectric infrared sensors. These sensors include band pass filters capable of penetrating previously determined wavelength bands. Detected signals are aplified by an amplifier circuit and then converted into a digital signal by an A/D converter. A microprocessor applies period detection and filtering based upon the dividing period of the chopper to the digital signal to return the divided signals to a continuous signal sequence. The wavelength band of detecting infrared rays are set up so as to efficiently detect the radiation of the heating body. Then the relative ratio of intensity values of plural infrared-ray radiation bands including the intensity of infrared ray existing the resonance radiation area of CO2 is found out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detection method for detecting a fire by detecting infrared rays emitted from a fire source, and particularly to detect infrared rays of multiple wavelengths simultaneously to distinguish between fire and non-fire. Fire detection method to clarify The present invention provides a method for effective fire detection regardless of the state of a fire such as a smoky fire or a flaming fire.

[0002]

2. Description of the Related Art Conventionally, a flame detection method for detecting infrared rays emitted from a flame has been put into practical use. Also, in these flame detection methods, the method that mainly detects the characteristic spectral line (4.4 μm band; CO ₂ resonance radiation band) emitted from the flame is the mainstream, but there are several methods that reduce malfunctions due to infrared sources other than flames. Some attempts have been proposed. For example, Japanese Patent Laid-Open No. 50-
No. 2497 detects the radiation dose at 4.3 μm and two wavelengths before and after it, and judges it as a flame when the radiation dose at 4.3 μm and other two wavelengths exceeds a certain value. Japanese Patent Laid-Open No. 57-96492 proposes to detect the occurrence of a flame by determining whether or not a valley exists between two convex portions.

In addition, JP-A-61-32195 discloses a first radiation detecting means for detecting radiation having a wavelength in the near infrared region and a second radiation detecting means for detecting radiation having a wavelength in the photographic infrared region. Calculating means for receiving output signals from the first and second radiation detecting means and calculating a logical combination of the output signals based on a level difference and synchronism of these output signals, and a combined output signal from the calculating means Discloses a fire detection device including a detection means for discriminating between a fire signal and a noise signal. This is because the flaming fire and the visible light noise have synchronism in the correlation of infrared rays of 2.3 μm and 0.9 μm, the smoky fire does not show the synchrony, and the flaming fire and the smoky fire are close to each other. Taking advantage of the fact that the infrared intensity is higher than the photographic infrared intensity and the visible light noise is the near-infrared intensity is lower than the photographic infrared intensity, the two types of radiation are compared to distinguish between fire and visible light noise, and flaming fire and smoke. It distinguishes between fires.

However, in the method of judging non-fire when the radiant intensity of visible light or near-infrared region is large compared to the radiant intensity of infrared region such as electric light, false alarms due to ordinary electric lights are reduced, but other than fire. If it is a heating element that does not emit visible or near-infrared rays or is weak, it is determined to be a fire and a false alarm is issued. That is, an electric heater or the like gives a false alarm and its application is largely restricted. Also, 4.3
Detects the radiation dose at μm and two wavelengths around it,
In the method of judging as a flame when the radiation dose at 4.3 μm and other two wavelengths exceeds a certain value, it is possible to detect the flame, but the flame originates from a fire or becomes a useful heat source. It cannot be detected whether it comes from. That is, there is a drawback that an erroneous report is generated by a flame of a gas range, a gas stove, or the like. Furthermore, by comparing the level difference and synchronism of the two types of radiation of 2.3 μm and 0.9 μm, it is possible to distinguish between fire and visible light noise, and to distinguish between flaming fire and smoldering fire. However, there is no compensation that the synchronism mentioned here is always seen depending on the burning method, and reliability is lacking.

The present inventors have responded to such a situation by detecting infrared rays emitted from an infrared source in a plurality of wavelength bands,
A highly reliable fire detection method is established by including a signal processing circuit that determines whether or not there is a fire based on the detection output of the infrared detector and the temporal change in the ratio of the detection output.

For example, the present inventors have filed Japanese Patent Application No. 03-345.
47, a short-wavelength infrared wavelength band that mainly detects relatively high-temperature heat generation, a long-wavelength infrared wavelength band that mainly detects relatively low-temperature heat generation, and CO2 resonance radiation that detects the presence or absence of a flame. Each wavelength band is detected, and these wavelength bands are used to determine the radiation spectrum of combustible substances in the smoldered state, various types of loss when infrared rays propagate in the atmosphere, and the housing required for configuring a fire detector. After considering the loss etc. in the body,
2.8 μm to 3.2 μm, 4.2 μm to 4.6 μm, 4.6 μm to 5.5
We provided a fire detection method that identifies four wavelength bands of μm and 8.0 μm to 10.0 μm and detects them. These wavelength bands are, first, as a wavelength pair for detecting high temperature heat generation, and as a wavelength pair for detecting low temperature heat generation.
2 wavelength bands, and a wavelength band for detecting the presence or absence of flame.

In Japanese Patent Application No. 03-34547, the temperature of the infrared source is calculated based on the ratio of the infrared intensities in the above wavelength bands, and the infrared intensity in any of the above wavelength bands is obtained from this temperature to obtain the infrared radiation intensity. And the fire situation is determined by calculating the heat generation area as follows based on the output of the infrared detector that detects the wavelength band.

Let .lambda.1, .lambda.2, ... .lambda.n (n = integer of 2 or more) be the detection wavelength bands, and V1, V2, ... Vn are the detection outputs of the respective wavelength bands detected by the infrared detector D. It is assumed that these detection outputs accurately reflect the infrared intensity of each wavelength band incident on the infrared detector D. By the way, according to Planck's radiation law, the radiant intensity per unit area of infrared rays radiated by a body at a certain temperature T into a half space at a wavelength λ is expressed by the following equation.

[0009]

[Equation 1]

Here, C1 and C2 are C1 = 2πhc2,
It is a constant determined by C2 = hc / k. However, h is Planck's constant, c is light velocity, and k is Boltzmann's constant.

In the above equation (1), two detection wavelength bands λ1 and λ2
Substituting the radiant infrared intensities P1 and P2 in that wavelength band and deriving an approximate expression for obtaining the temperature T,

[Equation 2] Here, if there is no absorption between the infrared source S and the infrared detector D for both λ1 and λ2, P1 and P2 in the above equation (2) can be replaced with V1 and V2. That is,

[Equation 3] Becomes From the equation (3), the temperature of the infrared source can be obtained by detecting infrared rays of two different wavelengths.

Next, the blackbody radiation intensity per unit area at λ1 or λ2 from the temperature T obtained by the above equation (3) (this is designated as P1 'or P2') is Planck's radiation law, that is, (1 ) Equation. On the other hand, the intensity of infrared rays incident on the infrared detector D depends on the distance L from the infrared source S to 1 / 2π.
It becomes L2. Therefore, the infrared ray intensity P1 ″ or P2 ″ to be incident on the infrared ray detecting section D from the infrared ray source having an area having the obtained temperature T (s times the unit area) is 2πL2 in P1 ′ or P2 ′. It is a value obtained by multiplying s. That is, P1 ″ = P1 ′ × 2πL2 × S (4) P2 ″ = P2 ′ × 2πL2 × S (5) Since it is assumed that the output of the infrared detector accurately reflects the intensity of the incident infrared rays, P1 or P2 can be found from V1 or V2 by using the above equations (3) and (2). Therefore, if the distance L is known, the actually detected incident infrared ray intensity P1 or P2 and the calculated incident infrared ray intensity P
The ratio with 1 "or P2" represents the area s of the infrared source S as can be seen from the equations (4) and (5).

Further, by using the wavelength band for detecting the CO ₂ resonance radiation band, the infrared of the black body radiation in the CO ₂ resonance radiation band is calculated by the formula (1) from the temperature and heat generation area of the infrared source obtained by the above means. calculating the intensity Pco ₂ ', determined infrared intensity Pco ₂ "to be incident on the infrared detection portion in the same manner as such the P1, calculates a ratio of the actual and observed Pco ₂ thereto. here, Pco ₂ If ">> Pco ₂ , the infrared source is accompanied by a flame. In this way, the fire situation is grasped and the fire alarm is issued.

[0014]

However, in the above-mentioned fire detection method, there is a slight difference in the detection result between the heating element without flame and the heating element with flame. That is, in a heating element accompanied by a flame, the resonance radiation of CO ₂ (4.4 μm band), which is said to be peculiar to the flame, is extremely strong, but in addition, various radiation around 5 μm due to H ₂ O radiation etc. It turned out to appear. As a result, in the case of a heating element accompanied by a flame, there is a problem that the scale of the heating element cannot be accurately determined.

[0015]

In order to achieve the above object, the present invention (1) detects infrared intensities in a plurality of infrared radiation bands including a resonance radiation pair of CO ₂ and compares the detected values with each other. In a fire detector that determines whether or not there is a fire based on the ratio and absolute value and their temporal changes, the intensities of multiple infrared radiation bands, including the temperature of the object to be detected, including the intensity of infrared rays at least in the CO ₂ resonance radiation region. Fire detection method, which is calculated by the relative ratio of. (2) When the detected object emits a flame, the relative value and absolute value of the value obtained by subtracting the characteristic radiation component of the flame from the intensity of the detected infrared rays, and the temperature and area of the detected object from their temporal changes. A fire detection method characterized by calculating. (3) In (1) above, the infrared radiation band to be detected is
2.8 μm to 3.2 μm, 4.2 μm to 4.6 μm, 4.6 μm to 5.5 μ
Fire detection method characterized by m, 8.0 μm to 10.0 μm. Invented

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be specifically described below. FIG. 1 shows an example of the configuration of a fire detector to which the present invention is applied. In this example, a chopper periodically divides infrared rays emitted from a fire source or a similar heat source,
Four pyroelectric infrared sensors detect four different wavelength bands. These sensors have a built-in bandpass filter that transmits a predetermined wavelength band. However, even with four or less pyroelectric infrared sensors, a method of detecting the wavelength divided into four using the switching means may be used. Further, even with only four or less pyroelectric infrared sensors, a method of detecting four kinds of wavelength bands by using the switching means may be adopted. The signal detected by each sensor is amplified by an amplifier circuit and then converted into a digital signal by an A / D converter. The microprocessor performs synchronous detection and filtering on the digital signal according to the division cycle of the chopper, and returns the signal divided by the chopper to a continuous signal sequence. Furthermore, the signal sequence obtained here is converted into a signal sequence for communication and digitally transmitted to the host computer.

The infrared wavelength band detected in the example of FIG. 1 is a wavelength band for efficiently detecting the radiation of the heating element from a low temperature region to a high temperature region as shown in FIG. That is, the center wavelength is 3 μm, the half width is 0.4 μm, the center wavelength is 4.4 μm, the half width is 0.4
μm, center wavelength 5.5 μm half width 0.8 μm, center wavelength 8.5 μm
The half-width of m is 1.0 μm. Regarding the above wavelength band, the radiation of the heating element in the high temperature region is mainly detected, and the heating element in the high temperature region of 400 ° C. or higher is monitored in combination with the infrared intensity detected in the wavelength band. The presence or absence of flame is monitored for the wavelength band. The wavelength band is a wavelength band that efficiently detects from low temperature to high temperature, and in combination with the wavelength band, it monitors the heating element in the high temperature range.
The heating element in the low temperature range is monitored in combination with the wavelength band.
As for the wavelength band, the radiation of the low-temperature heating element below 400 ° C is efficiently detected, and the heating element in the low-temperature region below 400 ° C is monitored in combination with the wavelength band. In the process from a smoldering state to a fire, a low temperature heating element gradually increases in temperature and expands. Therefore, it is necessary to monitor the temperature of the heat source in a wide temperature range from low temperature to high temperature.

The radiation component peculiar to the flame is such that the component in the wavelength band is substantially constant regardless of the size and quality of the flame, but the amount contained in the total radiation varies depending on the size and quality of the flame. The radiation of a flame is divided into a radiation part of a black body and a radiation part peculiar to the flame in the flame, and is the sum of the radiation of the black body part and the radiation peculiar to the flame. Further, the amount of the radiation component peculiar to the flame changes depending on the size of the flame. Here, the wavelength band in which the radiation peculiar to the flame appears is the wavelength band that is a resonant radiator of CO ₂ mainly, but the radiation peculiar to the flame also appears in the wavelength band. Radiation appearing in the wavelength band is considered to be water generated by combustion.

FIG. 3 shows that the temperature of the object to be detected is at least CO ₂
2 is an example showing the relative ratios of the intensities of a plurality of infrared radiation bands including the intensity of infrared rays in the resonance radiation region of, and when performing an experiment to detect various heating elements in the fire detector having the configuration shown in FIG. The relative ratio of the sensor output in each wavelength band is shown. The radiation component peculiar to a flame has a component ratio at the FR point in Fig. 3 in the wavelength band and the wavelength band. Centering on this point, the ratio of the sensor output due to the combustion of different combustibles is on a straight line. In other words, the wavelength band and the radiation component peculiar to the flame in all kinds of flames are FR
The component ratio is represented by dots. If you subtract the amount that the flame has, it will gather at a certain point on the line of blackbody radiation regardless of the size of the flame.

Radiation of flame means C generated by combustion.
It is a superposition of resonance radiation due to molecular vibrations of O ₂ , H ₂ O, etc. and thermal radiation due to solid particles such as graphite generated by combustion. The radiation of solid particles is mostly distributed over the flame and is the radiation of particles that are dispersed in a gas, and is therefore translucent. And even if this part is a translucent body,
If the flame is large enough, the emissivity can be considered to be almost 1. Also, the radiation peculiar to the flame due to CO ₂ , H ₂ O, etc. has a very high radiation efficiency, and is emitted from the surface of the flame. Therefore, for example, the radiation accompanying the combustion of normal heptane is drawn between the point a, which is the thermal radiation due to solid particles such as graphite generated by the combustion, and the FR point, which is the radiation peculiar to the flame due to CO ₂ , H ₂ O, etc. It has a radiation component on a straight line. Similarly, the radiation accompanying the combustion of methanol becomes the radiation component on the straight line between the point b and the FR point.

The flame temperature is highest in the gas body in the outer layer of the flame. Therefore, the temperature that causes thermal radiation is often not the maximum temperature of the flame, but when considering the scale of the flame as a whole, the radiation of the flame as a whole, that is, solid particles such as graphite generated by combustion, should be followed according to the above idea. It is better to consider the heat radiation by.

The calculation method for obtaining this temperature will be examined below. In the example of FIG. 3, the FR point, which is the origin of the straight line showing the characteristic of each flame of normal heptane and methanol, has a component ratio of wavelength band: wavelength band = 74: 26. Therefore, a phase diagram with this point as the apex may be considered.

Considering in this way, the component of thermal radiation in the flame can be separated by subtracting the radiation peculiar to the flame represented by the FR point from the actually detected radiation component of the flame. You will ride on the curve of the black body radiation inside. If such a process is performed, the temperature can be obtained by the calculation of the equation (3) from the ratio of the wavelength band and the wavelength band as in the case of the temperature calculation of the usual black body radiation. Therefore, the radiation component of the flame may be subtracted from the wavelength band.

A specific calculation example will be shown below. In this calculation example, an approximate calculation is performed in order to simplify the calculation. It can be seen from the examination of FIG. 3 etc. that the characteristic of the curve of the black body radiation is that the ratio of the wavelength band is small with respect to temperature and is about 20% of the total of the three wavelengths. Therefore, by subtracting the flame-specific component so that the ratio of the wavelength band is about 20% of the total of the three wavelengths of wavelength band-wavelength band-wavelength band, it is possible to leave almost a blackbody radiation component. here,
The standard of the ratio of the wavelength band after subtraction is 700 ℃ ~ 1000 ℃
The error can be reduced by adjusting to the blackbody radiation of.
In this case, the error given to the temperature calculation result is at most 20.
It is about ℃. If this is adjusted to blackbody radiation below 500 ° C, the error at high temperature becomes large.

The calculation procedure will be described below. First, subtract the radiation component peculiar to the flame before determining the relative ratio of the intensities of the infrared radiation bands including the infrared radiation intensity at least in the resonance radiation region of CO ₂ to the temperature of the object to be detected. The output value of the sensor for each component is V1, V2,
Let V3, and let Vx be the value subtracted as a component peculiar to the flame. Vx
Is the sum of the wavelength band and the flame-specific components of the wavelength band,
The respective ratios are Vf2 and Vf3. At point c in Fig. 4, Vx is the distance from point c on the extension of the straight line from FR point to point c to the curve of black body radiation, of which the component of the wavelength band is Vf2 and the component of the wavelength band is It is Vf3. Also, if the ratio of the wavelength band in the reference blackbody radiation is R2, Therefore, Becomes It is sufficient to subtract the radiation component of the flame from the wavelength band and the wavelength band using Vx obtained here. The flame temperature can be obtained by applying the value of the wavelength band and the value of the wavelength band corrected here to the equation (3). The area, the CO ₂ ratio is calculated temperature obtained here, the area for the wavelength band, CO ₂
The ratio is obtained by applying equations (4) and (5) to the wavelength band.

The temperature and area of the infrared source are obtained by the means described above. By the way, even if the temperature of the infrared source is high, if the size, that is, the area is small, it is not a fire, and conversely, if the temperature is low and the area is large, there is a high possibility of fire. What is important in considering a heat source in all states is the amount of heat that the heat source gives to the surroundings. That is, if the amount of heat given to the surroundings is large, the risk of fire spread increases and the expansion speed also increases. The amount of heat that the fire source gives to the surroundings is determined by the amount of radiant energy from the fire source. Therefore, the amount of radiant energy can be considered as the scale of the fire source. The radiant energy W of the heat source at a certain temperature T and area s is expressed as W = T4σ · s (W) (8) from the Stefan-Boltzmann law. Here, σ is the Stefan-Boltzmann constant, and σ = 5.673 × 10 ⁻¹² (W / cm ² · deg ⁴ ). Therefore, the scale of the fire source can be determined from the temperature and area of the infrared source.

In this embodiment, an alarm is issued when the amount of radiant energy obtained by the above means exceeds the amount of heat generated in a dangerous space in the target space. Regarding a general fire, it is said that the calorific value of the fire source is 5 kW to 20 kW, which is dangerous, that is, a person in the space feels dangerous. Of course, this value has a character that can be changed depending on the size of the target space, the use, and the like.
In addition, by providing one or more subdivisions for the value smaller than the heat generation amount in the dangerous state, and categorizing the danger stepwise and issuing an alarm each time the radiant energy amount exceeds each division, an early warning From the state, it is possible to issue a warning of caution, which makes it possible not only to detect a fire with higher accuracy but also to facilitate the initial response.

Further, by paying attention to the increase in the amount of radiant energy, it is possible to grasp the change in the state of the fire more accurately. That is, when the amount of radiant energy is large and the amount of radiant energy tends to increase, the possibility of fire is extremely high. In addition, even if the amount of radiant energy is large, if it does not change with time, it is often a useful flame such as heating, not a fire. Therefore, by issuing an alarm based on the rate of increase in the amount of radiant energy, it is possible to detect a fire reliably from an earlier stage.

The rate of increase in radiant energy is obtained from the rate of change in the calculated amount of radiant energy over a certain period of time. As this method, the calculated value of the radiant energy is stored in a time series for a certain period of time, and the time series value is subjected to high-frequency cutoff filtering such as moving average, and then the two radiant energy values separated by a certain period of time are compared. Based on the time-series values stored for a certain period of time, a method of obtaining the tendency of change from these values by the least square method is used. The storage time for calculating the rate of increase is preferably 10 seconds or more, but is preferably 3 minutes or less to avoid a delay in the alarm.

The criterion for fire judgment is that if the rate of increase in the amount of radiant energy exceeds a predetermined constant value, or if the rate of increase in radiant energy is divided into one or more predetermined stages, the rate of increase in radiant energy is the heat source. There is a case where the amount of radiant energy of the heat source shows an increase of a certain rate or more, and the rate of increase is divided into one or more predetermined stepwise division ratios of the radiant energy of the heat source. These are appropriately selected according to the requirements determined by the space and the like. Usually, about 1 to 5 is suitable for this division. The alarm is determined when the heat source is judged to be a fire when the rate of increase in the amount of radiant energy exceeds the above criteria or when it falls within the above categories, and is determined by, for example, the amount of radiant energy according to each step of the rate of increase. There are cases in which a six-level alarm is transferred to a higher alarm, which is also appropriately selected according to the specifications of the target space.

[0031]

EXAMPLE As an example, an example in which the fire detection method according to the present invention is applied to the fire detector having the configuration shown in FIG. In this embodiment, the detection wavelength band of each sensor of the detection unit shown in FIG. 1 is 3.0 ± 0.2 μm, 4.4 ± 0.2 μm, 5.0 ± 0.4 μm.
m, 8.5 ± 0.5 μm. Calculation formulas (1) to (8) are stored in the host computer, and the temperature, the area of the heating element, the presence or absence of a flame, and the radiant heat amount are calculated. Further, in the host computer, when the output of the sensor is 100 times or less of the noise level, filtering processing for noise reduction is performed. The time constant of the filtering process is 8 seconds when the output of the difference sensor is 100 times or less of the noise level, and the time constant is increased when the output of the sensor is small and 64 seconds when the output of the sensor is 10 times or less. I am trying. Fires are judged in 6 stages based on the amount of radiant heat. Furthermore, the increase rate of radiant heat is obtained by the method of least squares, and if this is 1 W / sec or more, it is assumed that the heating element is expanding,
If it is 10 W / sec or more, it is said to be expanding rapidly. If the fire is being expanded, the classification of fire determination is advanced to the one-stage risk side, and if it is being expanded rapidly, it is advanced to the two-stage risk side. The storage time when performing the least squares method is 20 seconds when the output value of the sensor is 100 times the noise level or more, but when the output of the sensor is small, the storage time is lengthened and the sensor If the output is less than 10 times the noise level, it is set to 3 minutes. In this embodiment, the FR point in FIG. 3 is set as wavelength band: wavelength band: = 74: 26. Also, R in equation (6)
2 is set based on 700 ° C blackbody radiation.

FIG. 5 is an experimental comparison of how the conventional fire detection method and the fire detection method of the present invention determine the scale of the heating element. This experiment uses normal heptane combustion. Burn normal heptane in square plates of various sizes and burn 10 m
This is the case when it is detected from the distance. In the conventional fire detection method, a large error occurs when the scale of the heating element is small, but it can be seen that the error is small in the present embodiment. When such an error occurs, the scale of combustion in the initial stage of the fire cannot be grasped, which causes a delay in the initial response. On the other hand, according to the fire detection method of the present invention, it is understood that the error is small even when the scale of the heating element is small.

[0033]

According to the fire detection method of the present invention, it is possible to accurately determine the scale of a heating element accompanied by a flame. FIG. 5 is an experimental comparison of how the conventional fire detection method and the fire detection method of the present invention determine the scale of the heating element. This experiment uses normal heptane combustion. This is the case when normal heptane placed in square plates of various sizes is burned and detected from a distance of 10 m. It can be seen that the conventional fire detection method causes a large error when the scale of the heating element is small.
When such an error occurs, the scale of combustion in the initial stage of the fire cannot be grasped, which causes a delay in the initial response. On the other hand, according to the fire detection method of the present invention, it is understood that the error is small even when the scale of the heating element is small. Therefore, appropriate measures can be taken in the early stages of the fire.

[Brief description of drawings]

1 shows an example of a detector according to the invention.

FIG. 2 shows a detection wavelength band in the present invention.

FIG. 3 shows relative ratios of sensor outputs in respective wavelength bands when an experiment for detecting various heating elements was performed in the fire detector having the configuration shown in FIG.

FIG. 4 is a reference diagram of a processing procedure formula in the present invention.

FIG. 5 is a comparison of the normal heptane combustion scale determination between the conventional fire detection method and the fire detection method according to the present invention.

Claims (3)

[Claims] 1. A fire which detects infrared intensities in a plurality of infrared radiation bands including a resonance radiation band of CO ₂ and determines whether or not a fire is detected based on a relative ratio and absolute value of the detected values and their temporal changes. A fire detection method, wherein a detector calculates the temperature of an object to be detected by a relative ratio of the intensities of a plurality of infrared radiation bands including the intensity of infrared rays in at least the resonance radiation region of CO ₂ . 2. When the object to be detected emits a flame, the relative value and absolute value of a value obtained by subtracting the characteristic radiation component of the flame from the intensity of the detected infrared ray and the temperature of the object to be detected from their temporal changes. A fire detection method characterized by calculating an area. 3. The infrared radiation band to be detected according to claim 1, which is 2.8 μm to 3.2 μm, 4.2 μm to 4.6 μm, 4.6 μm
Fire detection method characterized by 5.5 μm, 8.0 μm to 10.0 μm.