JPH04273399A - Method and device for fire discrimination - Google Patents

Abstract

PURPOSE:To permit early and correct fire detection and securely detect the generation of noxious gas due to a fire by discriminating the existance from the absence of gas due to the fire by means of an absorption spectrum of infrared rays. CONSTITUTION:A compensation cell 7 is microscopically connected to an air introducing pipe for in a supervised area. Therefore, the air in the compensation cell 7 is sufficiently delayed as against the environmental change in the supervised area in comparison with the air in a measuring cell 5. The air in the measuring cell 5 and the compensation cell 7 is irradiated with infrared rays from a light source 6 via a reflection mirror. Two light beams that pass through the cells 5 and 7 are alternately intercepted by a sector mirror 8 and, after passing through a slit 9, are turned into spectrums by a prism 10. Then, they pass through a slit 11 and are condensed by a detector 12. The detector 12 outputs the difference between the intensity of the light beam passing through the compensation cell 7 and that passing through the measuring cell 5 to a signal processing part (not shown in the figure). The signal processing part discriminates the existance from the absence of absorption at a specified level to see whether a specific gas is generated or not.

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 and device, and more particularly to a fire detection method and device for determining the occurrence of a fire by detecting the presence of gas in the air.

0002

2. Description of the Related Art Conventionally, a common method for detecting a fire is to monitor heat and smoke in a monitoring area, and determine a fire when the temperature exceeds a predetermined threshold or a predetermined rate of increase. In addition, methods for early and accurate fire detection are being considered, such as methods that combine heat and smoke or consider changes in detected values over time.

[0003] In recent years, attention has been paid to combustion gases, ie, carbon monoxide, hydrogen cyanide, and other odors, which are initially released when a fire occurs. A method of detecting a fire based on a change in the resistance value of a semiconductor element due to these emitted gases is being considered. but,
In order to detect odors and the like using semiconductor devices, it is necessary to distinguish between the detection of other gases, such as alcohol and aromas, and it is difficult to obtain sufficient selectivity due to the electrical reactivity of odors. Many fire accidents are caused by poisoning by toxic gases, and it is also important to determine whether such gases are generated.

0004

[Means for Solving the Problems] Therefore, according to the present invention, in order to solve the above problems, the air in a monitoring area is irradiated with infrared rays, and when a gas is present in the air, the dipole moment of the vibration of molecules changes. The presence of gas caused by fire can be detected from its spectrum, and the toxicity of the gas can also be determined.

[0005]

[Action] When infrared rays are irradiated into a gas, absorption of infrared rays occurs. This absorption of infrared rays is based on molecular vibrations and is related to minute displacements of all atoms within the molecule, so all compounds It exhibits a unique absorption shape, which can be used to determine the presence of a compound. Furthermore, there is absorption unique to atomic groups, and toxic functional groups can be identified and detected regardless of the molecule. Therefore, by irradiating gas in the air with infrared rays and determining its absorption spectrum, it is possible to reliably determine the amount and quality of gas generated by a fire.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of the present invention,
Reference numeral 1 denotes a detection section, 2 an air inlet pipe for the monitoring area, 3 an exhaust pipe, and 4 a signal processing section composed of a microprocessor and the like.

Further, FIG. 2 is a diagram showing the internal configuration of the detection section 1 in FIG. 1, and in FIG. 7 is a compensation cell that is also connected to the inlet pipe 2 and the exhaust pipe 3. Air from the monitoring area passes through the measurement cell 5 through the introduction pipe 2 without any obstruction, but the compensation cell 7 has only a small connection to the introduction pipe 2, so even if a fire breaks out in the monitoring area, it will not be immediately affected. It is configured to prevent gas from flowing in. 6 is a light source for irradiating the measurement cell 5 and the compensation cell 7 with infrared rays; 8 is a sector mirror that alternately blocks and passes the infrared rays that have passed through the measurement cell 5 and the compensation cell 7; 9 is a slit; 10
1 is a prism for separating infrared rays that have passed through the measurement cell 5 and the compensation cell 7; 11 is a slit; and 12 is a detector.

In the above configuration, the air in the monitoring area that has been sent to the measurement cell 5 of the detection unit 1 through the inlet pipe 2 is exhausted through the exhaust pipe 3, and in this way, new air in the monitoring area is always added. However, compensation cell 7 is taking in inlet pipe 2.
Since the air in the compensation cell 7 is only slightly connected to the air in the measurement cell 5, the air in the compensation cell 7 lags sufficiently behind the environmental changes in the monitored area compared to the air in the measurement cell 5. The air inside the measurement cell 5 and the compensation cell 7 is irradiated with infrared rays from the light source 6 via a reflecting mirror, and the two rays of light that have been irradiated and passed through each cell are alternately blocked by the sector mirror 8 and reflected. The mirror passes through slit 9, the light is separated by the prism, and then the light passes through slit 1 again.
1 and is focused on a detector 12.

Usually, a silicon carbide rod or a Nernst lamp is used as the light source 6, and a thermocouple or a bolometer is used as the detector 12. The spectral range of prism 10 is usually 40
It is sufficient if the detection can be performed up to 0.00 cm-1, but if the purpose is only to detect fire, it is sufficient to further narrow down the range to a specific range.

The detector 12 outputs the intensity difference between the light passing through the compensation cell 7 and the measurement cell 5 to the signal processing section 4 shown in FIG. Perform comparison processing. If there is no change in the air in the monitored area,
That is, if the air is in the same state for a long time, there is no difference in intensity between the compensation cell 7 and the measurement cell 5, which indicates that there is no abnormality.

[0011] If there is an intensity difference, this is based on the change in the air, that is, the gas component that has been mixed in or invaded, and therefore, it is important to know whether there is a predetermined level of absorption at a specific wavelength in the intensity difference. By determining this, it is possible to know whether a specific gas has been generated or not.

[0012] Here, we will discuss the gases generated during a fire and their infrared absorption wavelengths.The gases generated during a fire vary depending on the composition of the combustion material and the burning conditions, and various gases are generated. As a general trend, CO and CO2 are always generated, and gases are released depending on the chemical composition of the material through thermal decomposition and combustion. For example, in vinyl chloride, phosgene,
It has been detected that hydrocarbons such as chlorine, HCl, benzene and methane are released, and acrylonitrile releases HC
Releases N, methane, etc., and in urethane foam, HCN
, ethylene, etc. have been detected, and CO,
Other than CO2, simple hydrocarbons such as NH3, HCN, alcohols, aldehydes, and nitriles are mainly generated. Chemical asphyxiating gases due to their combination with hemoglobin include CO and HCN, and gases irritating to the eyes and respiratory tract include HCl, NH3, phosgene, and NO.
2nd grade is known.

[0013] When a fire occurs, the gas from the fire increases in the air, so the absorption of infrared rays also increases. For example, CO exhibits absorption at 2143 cm-1 due to a triple bond, and phosgene exhibits absorption at 1828 cm-1 due to stretching vibrations of C=O bonds. Other main factors include monochloric C-C1 at 750 x 700 cm-1.
Stretching vibration, C≡N of nitrile near 2250cm-1
Stretching vibration, S of sulfonic acid near 1350 cm-1
=O stretching vibration, large H of water near 3300cm-1
-OH stretching vibration and N→O stretching vibration near 1250 cm-1.

[0014] Therefore, it is possible to discriminate a fire based on the target infrared absorption, and it is also possible to discriminate fire and its danger based on the combination of the infrared absorption and the various infrared absorptions described above. Can be done. It is desirable to determine which gas to detect or which wavelength to perform for each installation environment based on the above-mentioned infrared absorption mode.

[0015] In this way, the signal processing unit 4 is preliminarily stored with specific wavelengths to be subjected to wavelength discrimination, and as a result of the comparison process, the difference in the intensity of the transmitted light between the compensation cell 7 and the measurement cell 5, If there is a predetermined level of absorption at the specific wavelength stored in the memory, it is determined that a fire has occurred, and the danger associated with the occurrence of the fire is also determined, and a signal indicating this is output. Based on the signal, necessary fire operations are performed, such as sounding a fire alarm buzzer (not shown) and calculating and displaying the degree of toxic gas generation. If we can know the degree of toxic gas generation, we can empirically estimate what is burning.

In the above embodiment, the measurement cell 5 and the compensation cell 7 are provided to take the difference in the intensity of the light passing through the two, but the light passing through the measurement cell 5 is The signal is stored in memory, and the previous passing optical signal stored a predetermined time ago is compared with the current passing optical signal to determine whether there is an intensity difference, and if there is an intensity difference, ,
Similarly to the above, it may be determined based on the intensity difference whether or not there is a predetermined level of absorption at a specific wavelength. In this way, the compensation cell 7 becomes unnecessary.

In addition, in the detecting section 1, instead of constantly measuring infrared absorption, a semiconductor type gas sensor using a metal oxide or the like is separately provided, and the semiconductor type gas sensor or the like is installed separately.
It is also possible to start infrared absorption measurement only when a certain amount of gas generation is detected by the sensor.

Furthermore, in the above embodiment, a sampling method was shown in which the air in the monitoring area was introduced to the measurement cell 5 of the detection unit 1 through the introduction pipe 2, but the detection unit was made open to allow air in the monitoring area to be introduced into the measurement cell 5 of the detection unit 1. It may be installed directly on the ceiling or the like to directly irradiate the air in the monitoring area with infrared rays. In this way, the introduction pipe 2 and the exhaust pipe 3 become unnecessary.

It is also possible to input the infrared absorption level values at specific wavelengths obtained by the present invention into a neural network or fuzzy function using a microprocessor for each wavelength and process the values. Details of such a neural network are shown in, for example, Japanese Patent Application Laid-Open No. 2-105299 by the applicant, and details of fuzzy functions are shown in, for example, Japanese Patent Application Laid-Open No. 2-195495, also by the applicant. has been done. By using neural networks and fuzzy functions, it becomes possible to perform simple, rational, and even more detailed processing.

[0020]

As described above, according to the present invention, the air in the monitoring area is irradiated with infrared rays, and the presence or absence of gas in the air is detected from the absorption spectrum of the infrared rays. This has the effect of enabling early and accurate fire detection, and also reliably detecting the generation of toxic gases due to fire.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a fire discrimination device according to the present invention.

FIG. 2 is a diagram showing the internal configuration of the detection section 1 in FIG. 1.

[Explanation of symbols]

1 Detection part 4 Signal processing section 5 Measurement cell 6 Light source 7 Compensation cell 8 Sector mirror 10 Prism 12 Detector

Claims (5)

[Claims] Claim 1: The air in the monitoring area is irradiated with infrared rays, and when gas is present in the air, absorption is caused by vibrations that change the dipole moment of molecules. A fire discrimination method characterized by detecting the presence of a fire. Claim 2: When the air in the monitoring area is irradiated with infrared rays, when gas is present in the air, absorption is caused by vibrations that change the dipole moment of molecules. A fire discrimination method characterized by determining toxicity. 3. A light emitting means for irradiating infrared rays onto the air in the monitoring area, and a spectroscopic means for separating the light that has passed through the air.
Detection means for detecting the intensity of the separated light by wavelength;
A fire discriminating device comprising: discriminating means for discriminating gas caused by a fire from information of the detecting means. 4. A light emitting means for irradiating infrared rays onto the air in a monitoring area, and a spectroscopic means for separating light that has passed through the air,
Detection means for detecting the intensity of the separated light by wavelength;
a discriminating means for discriminating gas caused by a fire from information of the detecting means; a discriminating means for monitoring the amount of gas present in the air in the monitoring area, and when the amount of gas reaches a predetermined amount, the light emitting means, the spectroscopic means; A fire discriminating device comprising: a starting means for starting the detecting means and the discriminating means. 5. The fire discriminating device according to claim 3, wherein the discriminating means includes toxicity calculating means for calculating the degree of generation of toxic gas.