WO2022052319A1

WO2022052319A1 - Gas detection system and detection method

Info

Publication number: WO2022052319A1
Application number: PCT/CN2020/131091
Authority: WO
Inventors: 郗晓言
Original assignee: 北京中立格林传感科技股份有限公司
Priority date: 2020-09-14
Filing date: 2020-11-24
Publication date: 2022-03-17
Also published as: CN112033865A; GB202300525D0; GB2614967A

Abstract

A gas detection system and detection method, which are suitable for real-time online monitoring of the air quality of an air duct (10). The gas detection system comprises: a sampling module (110), which is used for collecting in real time a gas to be detected in the air duct (10); a detection module (120), which is connected to the sampling module (110), the detection module (120) detecting in real time the collected gas by means of a plurality of sensors; and an information processing module (130), which is connected to the detection module (120) and used for acquiring detection data of the detection module (120) and processing in real time the detection data to obtain a detection result. The detection module (120) comprises a first detection unit (121) and a second detection unit (122). The first detection unit (121) is connected to the second detection unit (122). By means of the first detection unit (121) performing preliminary detection and processing on the gas, and then the second detection unit (122) detects the gas. The detection data of the first detection unit (121) may also be used to compensate the second detection unit (122), so as to reduce the deviation of the detection result and enhance the stability and reliability of the detection result.

Description

Gas detection system and detection method

This application claims the priority of the Chinese patent application filed on September 14, 2020, with the application number of 202010964968.1 and the invention titled "Gas Detection System and Detection Method", the entire contents of which are incorporated into this application by reference.

technical field

The invention relates to gas detection technology, and more particularly, to a gas real-time detection system and detection method.

Background technique

Air quality has a very important impact on human health, and air pollutants are the predisposing factors for many diseases. At present, the harmful pollutants in the air mainly include: fine particulate matter (PM2.5) with a diameter of less than 2.5 microns and dust particles with a diameter of less than 10 microns PM10, as well as total volatile organic compounds (Volatile Organic Compounds, TVOC), carbon monoxide, Ozone, etc. PM2.5/PM10 is the main component of today's haze pollutants, TVOC includes aldehydes, benzene, ammonia and other volatile gases. With the improvement of environmental protection requirements, more and more factories need to install gas detection devices in the exhaust air ducts and public building air ducts to monitor the exhaust gas and whether the indoor air environment in public places meets the standards.

Most of the existing real-time gas detection devices can only detect a single gas in the air duct, such as monitoring carbon dioxide, carbon monoxide, etc. There are also very few detection devices that can be used to monitor PM2.5 or TVOC in the air duct, but they all use air pumping. The gas in the air duct is drawn into the detection device, and then the gas in the detection device is sensed and measured. The air pump is used for air extraction, the service life of the air pump is short, and the real-time long-term work is very prone to failure and damage. At the same time, due to the different pressure and flow rate of different air ducts, the pressure and flow rate in different time periods in the same air duct will change. If the air pump works intermittently, the gas flow rate will change, so that the measured value of PM2.5/PM10 will vary with the gas flow rate. Changes and unstable airflow cause large measurement deviations, which cannot guarantee measurement accuracy and precision. Further, the temperature and humidity in the air duct may also change, and the temperature and humidity changes will also affect the detection results of PM2.5/PM10 and TVOC. The TVOC measurement value in the prior art usually has a large deviation. Due to the different air quality concentrations in the air duct in different projects, the TVOC sensor cannot correctly find the reference point during long-term use, resulting in the inability to provide accurate TVOC values.

Therefore, designing a gas detection device suitable for long-term stable monitoring of multiple parameters in the air duct is an urgent problem to be solved at this stage.

SUMMARY OF THE INVENTION

In view of the above problems, the purpose of the present invention is to provide a gas detection system, the detection module of the gas detection system includes a sampling module for real-time collection of the gas to be measured in the air duct; the detection module has a plurality of sensors, the detection module is connected with the sampling module, and the detection module performs real-time detection on the collected gas to be measured through the plurality of sensors; an information processing module is connected with the detection module, and the information processing module is used to obtain the detection The detection data of the module is processed in real time to obtain detection results; wherein, the detection module includes a first detection unit and a second detection unit, and the first detection unit is connected to the second detection unit, The first detection unit includes a fan, and the fan controls the flow rate of the gas to be detected in the detection module within a predetermined range.

Preferably, the sensing detection data of the first detection unit is also used to compensate part of the sensors of the second detection unit.

Preferably, the second detection unit includes a particle sensor, and by controlling the rotational speed of the fan to obtain a constant flow of the gas to be measured, the detection data of the particle sensor is obtained at the same flow rate, so as to prevent the gas flow from affecting the detection data of the particle sensor Impact.

Preferably, the first detection unit includes a temperature and humidity sensor, the second detection unit includes a TVOC sensor and/or a particulate matter sensor, and the information processing module analyzes the TVOC sensor and/or the TVOC sensor according to the detection data of the temperature and humidity sensor. Or the particulate matter sensor performs data compensation processing to reduce the influence of temperature and humidity changes on the detection results of the TVOC sensor and/or the particulate matter sensor.

Preferably, when the ambient temperature is greater than T _a , temperature compensation is performed on the TVOC sensor and/or the particulate matter sensor; when the ambient humidity is greater than RH _a , humidity compensation is performed on the TVOC sensor and/or the particulate matter sensor, wherein T _a is a reference temperature value, RH _a is a reference humidity value, and the reference temperature value and the reference humidity value are pre-stored in the information processing module.

Preferably, the detection module includes a TVOC sensor, the information processing module pre-stores a reference reference value, calculates the TVOC measurement value through continuous reading, compares the measurement value with the TVOC reference reference value, and selects the TVOC reference reference value and the TVOC reference reference value. The smaller of the TVOC measurements was taken as the baseline value of TVOC.

Preferably, the collection module includes a collection tube, one end of the collection tube is connected to the detection module, and the other end extends into the air duct to collect the gas to be measured, and the collection tube is composed of two opposite sides, which are respectively provided with The airflow introduction slot and the airflow outlet slot, the airflow introduction slot is located on the windward side, and the airflow outlet slot is located on the leeward side. The gas to be tested enters the detection module from the airflow introduction slot on the windward side of the collection pipe. difference, the gas to be tested flows into the detection module from the airflow introduction slot, and then flows out through the airflow outlet slot.

Preferably, the plurality of sensors further include at least one of a carbon dioxide sensor, a carbon monoxide sensor, a formaldehyde sensor, an ozone sensor, a sulfide sensor, and a nitride sensor.

According to another aspect of the present invention, a gas detection method using the above-mentioned gas detection system is also provided, which is characterized by comprising the following steps: a sampling module obtains the gas to be measured in the air duct; The flow rate of the gas to be measured in the module is within the preset range; the temperature and humidity detection data of the gas to be measured is obtained through the temperature and humidity sensor; the detection data of particulate matter is obtained through the particulate matter sensor; the TVOC detection data of the gas to be measured is obtained through the TVOC sensor combined with the TVOC baseline value ; Compensate the particle detection data and TVOC detection data according to the temperature and humidity detection data, and obtain the detection result that the particle and TVOC have eliminated the influence of temperature and humidity.

Preferably, the method further includes: adjusting the TVOC baseline value, calculating the TVOC real-time measurement value by continuously reading, comparing the measurement value with the TVOC reference reference value pre-existing in the information processing module, and selecting the TVOC reference reference value and the smaller of the measured values as the baseline value of TVOC.

To sum up, the implementation of the present invention has the following advantages or beneficial effects: the gas detection system can monitor the air quality of the air duct online in real time, and the gas detection system divides the detection module into a first detection unit and a second detection unit. The first detection unit performs preliminary detection and processing of the gas to be measured, keeps the flow rate of the gas to be measured constant, and obtains the temperature and humidity detection data of the gas to be measured. , which can effectively improve the accuracy and reliability of the detection information of the second detection unit, and can also use the detection data of the first detection unit to compensate the detection information of the second detection unit, reducing the change of the detection items of the non-second detection unit. impact on its test results. Further, the gas detection system presets a TVOC reference reference value for TVOC detection, ensuring that in different use environments, there are standard baseline values as a reference. Of course, the system can also be based on the use environment conditions. TVOC baseline value. Correction and adjustment are made to ensure that the correct detection value can be output in different air quality environments. The detection system has strong reliability and long service life. The detection method based on the detection system, through flow control and temperature and humidity compensation, effectively reduces the influence of individual sensors on their detection results due to changes in non-detection items of the gas to be detected, and makes the detection results more accurate than the existing technology. It is stable and reliable, and can better feedback the actual situation of the gas to be measured.

Description of drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an embodiment of the gas detection system of the present invention.

FIG. 2 is a schematic structural diagram of an embodiment of the gas detection system of the present invention.

FIG. 3 is a schematic diagram of the detection method of the gas detection system of the present invention.

detailed description

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the various figures, the same elements are designated by the same or similar reference numerals. For the sake of clarity, various parts in the figures have not been drawn to scale.

However, the present invention is not limited only to these examples. In the following detailed description of the invention, some specific details are described in detail. The present invention can be fully understood by those skilled in the art without the description of these detailed parts. In order to avoid obscuring the essence of the present invention, well-known methods, procedures and processes are not described in detail.

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

1 is a schematic diagram of an embodiment of a gas detection system of the present invention. It can be seen from the figure that the gas detection system includes: a sampling module 110, a detection module 120 and an information processing module 130, wherein the detection module 120 includes a first detection unit 121 and a second detection unit 121. unit 122. One end of the collection module 110 is connected to the air duct 10, and the other end is connected to the detection module 120. Specifically, the arrows in the figure indicate the gas flow direction, and the gas to be measured in the air duct 10 passes through the sampling module 110 through the first detection unit 121 and enters the first detection unit 121. After the two detection units 122, it flows back into the air duct 10 via the first detection unit 121 and the sampling module 110; the information processing module 130 is electrically connected to the first detection unit 121 and the second detection unit 122 of the detection module 120, The first detection unit 121 and the second detection unit 122 are controlled and their detection information is acquired.

Further, the first detection unit 121 includes, for example, a fan, a temperature and humidity sensor, etc., and the second detection unit 122 includes, for example, a particulate matter sensor, a TVOC sensor, and the like. The flow rate of the gas to be measured is controlled within a predetermined range and the flow rate is kept stable, so that the particulate matter sensor can obtain particulate matter detection information at a specific flow rate to ensure that the detection information of the particulate matter sensor is not affected by the flow rate of the gas to be measured. Similarly, the temperature and humidity detection information of the gas to be measured is obtained through the temperature and humidity sensor, and the information processing module 130 compensates the detection information of the particulate matter sensor and the TVOC sensor according to the temperature and humidity monitoring information, so as to reduce the impact of the temperature and humidity changes of the gas to be measured on the particulate matter. And the influence of TVOC detection results, make the detection results more real and reliable, and reduce the occurrence of false fluctuations and false alarms. Of course, the information processing module 130 may also include a communication unit and an alarm unit (not shown in the figure), the communication unit is used for communicating with external devices and communication systems, and the communication unit includes wired communication RS485, Ethernet network interface, wireless communication WIFI At least one of GPRS and GPRS; wherein, the wired communication RS485 can be the basic communication interface, and one or more of the other three communication interfaces can be selected for use. The alarm unit is used to alarm the abnormal state. When the detection result exceeds the preset safe fluctuation range for a certain period of time, the alarm unit will issue an alarm by at least one of vibration, light and sound to remind relevant personnel to detect abnormal parameters so as to find out in time. Troubleshoot the problem.

Of course, in the gas detection system provided by the present invention, the baseline value will also be corrected periodically or according to the operation instruction according to the actual use environment. Taking the TVOC sensor as an example, the TVOC reference reference value is pre-stored in the information processing module 130. During detection, the TVOC reference reference value will be used as the baseline value at first. After a period of detection or in accordance with the operating instructions, the information processing module 130 will continuously correct the baseline value, and compare the TVOC detection information in the current environment with the TVOC reference benchmark. The smaller one is selected as the baseline value of the new TVOC, so as to calculate and output the TVOC detection result more accurately.

Certainly, carbon dioxide sensor, carbon monoxide sensor, formaldehyde sensor, ozone sensor, sulfide sensor, nitride sensor and other types of sensors may also be provided in the detection module 120 to detect various parameters of the gas to be measured.

2 is a schematic structural diagram of an embodiment of the gas detection system according to the present invention. In the figure, the gas flow direction in the air duct 10 is, for example, from left to right. 111 and flange 112, the collection tube 111 is designed with a pit tube, for example, the airflow introduction slot of the collection tube 111 is located on the windward side, the airflow outlet slot is located on the leeward side, and the gas to be tested enters the detection from the airflow introduction slot on the windward side of the collection tube 111. module, according to the pressure difference between the windward side and the leeward side of the collection tube 111, the gas to be tested flows into the detection module from the airflow introduction slot, and then flows out through the airflow outlet slot on the leeward side. The design does not require a pump drive, has a simple structure, saves energy, has a long service life, and is not easy to block, so that the system can run stably for a long time. For example, the flange 112 is used to fix the collection pipe 111, while ensuring the orientation of the collection pipe 111. For example, the flange 112 and the collection pipe 111 are integrally designed, and the direction of the windward side of the collection pipe can also be marked on the flange to ensure To ensure the correct installation direction, one end of the collection tube is connected to the detection module in the housing 20, and the other end extends into the air duct 10 to collect the gas to be measured.

Further, in the system, only part of the collection module 110 extends into the air duct 10, and the rest of the system is located outside the air duct 10, which effectively reduces the impact of the harsh environment in the air duct 10 on the system, and The flow of the gas to be measured is adjusted by the fan to keep the flow stable, so that the measured value of particulate matter (PM2.5/PM10) of the system is more accurate and stable, and no air pump is needed to extract the gas to be measured, the cost is lower, and the service life is longer. Maintenance free.

Fig. 3 is the detection method schematic diagram of the gas detection system of the present invention, and this detection method comprises the following steps:

The S10 sampling module obtains the gas to be measured in the air duct;

S20 controls the fan speed of the detection module to be constant; the fan is, for example, located at the airflow inlet of the detection module, and the flow rate of the gas to be measured in the detection module is stabilized within a predetermined range by controlling the speed of the fan;

S30 obtains the temperature and humidity detection data of the gas to be measured through the temperature and humidity sensor;

S40 obtains the particulate matter detection data through the particulate matter sensor; since the fan can control the flow of the gas to be measured in the detection module, when the flow of the gas to be measured is stable to a specific value, the particulate matter sensor detects the gas to be measured and obtains its particulate matter detection data, so that all The acquired particle detection data are all acquired under the same flow rate, which avoids the interference of different flow rates on particle detection.

The S50 obtains the TVOC detection data of the gas to be measured through the TVOC sensor, and further, can be combined with the TVOC baseline value to obtain the TVOC detection data of the gas to be measured, making the data more accurate;

S60 compensates the particulate matter and the TVOC detection data according to the temperature and humidity parameters to obtain a particulate matter measurement value and a TVOC measurement value. The specific compensation algorithm for particle detection and TVOC detection and the temperature characteristic curve and humidity characteristic curve of the corresponding sensor are pre-stored in the information processing module, and the corresponding compensation ratio is obtained according to the temperature and humidity detection data obtained by the temperature and humidity sensor and the characteristic curve. Compensate with TVOC detection data to obtain the detection results of particulate matter and TVOC, reduce the impact of temperature and humidity changes on the detection results of particulate matter and TVOC, and make the detection results more stable and reliable.

Further, the information processing module in the gas detection system of the present invention pre-stores the temperature characteristic curve and the humidity characteristic curve of the particulate matter sensor and TVOC sensor, and the characteristic curve, for example, is subjected to curve fitting according to a plurality of acquired detection data through multiple test detections. To obtain, of course, in order to further improve the accuracy of the characteristic curve, the curve can also be segmented and then fitted to obtain its characteristic curves in different intervals to improve the accuracy of the characteristic curve.

When the ambient temperature is greater than T _a , the following method is used to perform temperature compensation on the TVOC sensor, wherein T _a is a reference temperature value, and the reference temperature value T _a is pre-stored in the information processing module, and the specific compensation includes:

Calculate the sensor output value V _N after temperature compensation,

When V _N < V ₁ :

When V _N ≥ V ₁ :

Among them, V _N is the TVOC sensor output value after temperature compensation, V _r is the output value of the TVOC sensor before compensation, S _t is the compensation ratio obtained according to the temperature characteristic curve of the TVOC sensor, N ₀ , N ₁ , N ₂ is the TVOC calibration value of the three pre-stored calibration points, V ₀ , V ₁ , and V ₂ are the three output values corresponding to the three pre-stored calibration points respectively, and N is the TVOC measurement value after the final compensation.

Specifically, taking the temperature compensation of the TVOC sensor as an example, T _a is, for example, 20°C. If the current ambient temperature is 30°C, the temperature compensation is enabled. Refer to the temperature characteristic curve of the particulate matter sensor pre-stored in the information processing module, the temperature characteristic curve When the medium temperature is 20°C, the output value of the TVOC sensor is 1000, and the other parameters of the external environment except the temperature remain unchanged. When the temperature in the temperature characteristic curve is 30°C, the output value of the TVOC sensor is 800, then the current ambient temperature The compensation ratio S _t =800/1000, and then according to the compensation ratio S _t and the TVOC calibration values N ₀ , N ₁ , N ₂ stored in the information processing module and their corresponding calibration point output values V ₀ , V ₁ , V ₂ , And the output value V _r of the TVOC sensor before compensation is processed, and the final TVOC measurement value N after compensation is obtained according to the above compensation formula.

Similarly, the humidity compensation and the temperature and humidity compensation methods of the particle sensor are also similar to the above temperature compensation, which will not be repeated here. The temperature and humidity characteristic curves of the TVOC sensor and the particle sensor are different, and the compensation ratios are also different. Different compensation ratios are involved in the compensation calculation, so that the measured values of the sensor are closer to the actual parameters in the environment, enhance the accuracy of the measurement, and reduce the influence of cloudy and rainy days or temperature changes on the measured values of the sensor.

Further, in order to reduce the deviation of TVOC detection, the TVOC reference reference value is also pre-stored in the information processing module. When the TVOC sensor is detected, the TVOC reference reference value will be used as the baseline value at first, and after a period of detection or according to the operation command, the information processing module will correct and adjust the baseline value. By comparing the TVOC detection information in the current environment and the TVOC reference reference value, the smaller one is selected as the new TVOC baseline value for more accurate calculation. Output TVOC detection results to reduce detection bias.

The gas detection method reduces the influence of changes in some non-target detection items on the detection results, and alleviates the problems of drift and inaccuracy of measurement values in complex environments, which cannot reflect the actual situation. The detection method has a wide range of applicability and can be applied to Various scenarios.

To sum up, the implementation of the present invention has the following advantages or beneficial effects: the gas detection system can monitor the air quality of the air duct online in real time, and the gas detection system divides the detection module into a first detection unit and a second detection unit. unit, through the first detection unit to perform preliminary detection and processing of the gas to be measured, to keep the flow of the gas to be measured constant, and to obtain the specific flow and temperature and humidity detection data of the gas to be measured. The state is more stable, which can effectively improve the accuracy and reliability of the detection information of the second detection unit, and can also use the detection data of the first detection unit to compensate the detection information of the second detection unit to reduce the detection of non-second detection units. The impact of item changes on its detection results. Further, the gas detection system sets a TVOC reference value for TVOC detection, and the reference value can be used as a baseline value to ensure that there are standard baseline values as a reference in different use environments. Of course, the system can also be used according to The environment corrects and adjusts the TVOC baseline value to better detect and record the current environment and reflect the changes of various parameters of the gas to be measured. The detection system has strong reliability and long service life. The detection method based on the detection system, through flow control and temperature and humidity compensation, effectively reduces the influence of individual sensors on the detection results due to changes in the non-detection items of the gas to be measured, and makes the detection results more stable than the existing technology. It is reliable and can better feedback the actual situation of the gas to be measured.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

The embodiments according to the present invention are as described above, the drawings are to highlight the details of the technical solutions of the present invention, the proportions of each component are not drawn according to the actual scale, and the proportions and dimensions shown in the drawings should not limit the essence of the present invention Technical solutions, these embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments described. Obviously, many modifications and variations are possible in light of the above description. This specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can make good use of the present invention and modifications based on the present invention. The present invention is to be limited only by the claims and their full scope and equivalents.

Claims

A gas detection system, characterized in that it includes:

The sampling module is used to collect the gas to be measured in the air duct in real time;

a detection module, having a plurality of sensors, the detection module is connected with the sampling module, and the detection module performs real-time detection on the collected gas to be measured through the plurality of sensors;

an information processing module, connected to the detection module, the information processing module is used for acquiring detection data of the detection module, and performing real-time processing on the detection data to acquire detection results;

Wherein, the detection module includes a first detection unit and a second detection unit, the first detection unit is connected to the second detection unit, the first detection unit includes a fan, and the fan drives the detection module The flow rate of the gas to be tested is controlled within a predetermined range.
The gas detection system according to claim 1, wherein the sensing detection data of the first detection unit is further used to compensate some sensors of the second detection unit.
The gas detection system according to claim 1, wherein the second detection unit includes a particulate matter sensor, and the particulate matter sensor is obtained under the same flow rate by controlling the rotational speed of the fan to obtain a constant flow of the gas to be tested. to avoid the influence of gas flow on the detection data of particulate matter sensor.
The gas detection system according to claim 2, wherein the first detection unit includes a temperature and humidity sensor, the second detection unit includes a TVOC sensor and/or a particulate matter sensor, and the information processing module The detection data of the humidity sensor performs data compensation processing on the TVOC sensor and/or the particulate matter sensor, so as to reduce the influence of temperature and humidity changes on the detection result of the TVOC sensor and/or the particulate matter sensor.
The gas detection system according to claim 4, wherein when the ambient temperature is greater than Ta, temperature compensation is performed on the TVOC sensor ; when the ambient humidity is greater than RH a , humidity compensation is performed on the TVOC sensor, wherein , T a is a reference temperature value, RH a is a reference humidity value, and the reference temperature value and the reference humidity value are pre-stored in the information processing module.
The gas detection system according to claim 1, wherein the detection module comprises a TVOC sensor, the information processing module pre-stores a reference reference value, calculates the TVOC measurement value by continuously reading, and compares the measurement value with the TVOC reference reference Values are compared, and the smaller of the TVOC reference reference value and the TVOC measurement value is selected as the TVOC baseline value.
The gas detection system according to claim 1, wherein the collection module comprises a collection tube, one end of the collection tube is connected to the detection module, and the other end extends into the air duct to collect the gas to be measured, the The collection tube consists of two opposite sides, which are respectively provided with an airflow introduction slot and an airflow outlet slot. The airflow introduction slot is located on the windward side, and the airflow outlet slot is located on the leeward side. The gas to be tested enters the detection from the airflow introduction slot on the windward side of the collection tube. module, according to the pressure difference between the windward side and the leeward side of the collection pipe, the gas to be tested flows from the airflow introduction slot into the detection module, and then flows out through the airflow outlet slot.
The gas detection system of claim 4, wherein the plurality of sensors further comprises at least one of a carbon dioxide sensor, a carbon monoxide sensor, a formaldehyde sensor, an ozone sensor, a sulfide sensor, and a nitride sensor.
A gas detection method, comprising the following steps:

The sampling module obtains the gas to be measured in the air duct;

Control the fan speed of the detection module to be constant, so that the flow rate of the gas to be measured in the detection module is within the preset range;

Obtain the temperature and humidity detection data of the gas to be measured through the temperature and humidity sensor;

Obtain particle detection data through a particle sensor;

Obtain the TVOC detection data of the gas to be measured by combining the TVOC sensor with the TVOC baseline value;

The particulate matter detection data and TVOC detection data are compensated according to the temperature and humidity detection data to obtain a detection result in which the particulate matter and TVOC have eliminated the influence of temperature and humidity.
The detection method according to claim 9, further comprising:

Adjust the TVOC baseline value, calculate the TVOC real-time measurement value by continuously reading, compare the measurement value with the TVOC reference reference value pre-existing in the information processing module, and select the smaller of the TVOC reference reference value and the measurement value. as the baseline value of TVOC.