JP5081046B2 - Acetic acid or formic acid detector tube, indoor air quality monitoring method and building material quality evaluation method - Google Patents

Description

  The present invention relates to an acid gas detector tube capable of easily quantifying a very small amount of acid gas (acetic acid, formic acid) in the air, a method for monitoring indoor air quality, and a method for evaluating building material quality.

In art museums and museums, the presence of chemicals such as acetic acid and formic acid in the air adversely affects art and exhibits. Also, in the clean room related to electronic devices, these chemical substances are offensive odor and there is concern about the impact on workers.
Therefore, when constructing buildings such as museums, museums, clean rooms, etc., it is required to reduce the indoor concentration of such undesirable chemical substances as much as possible. It is necessary to strictly manage this. In addition, it is necessary to measure the concentration at the time of delivery.
On the other hand, it is necessary for the user to make efforts to maintain the indoor concentration of chemical substances at a low level in facility management. Specifically, the concentration of the above chemical substances in the air is periodically measured to affect the effects of artworks and products. I know.

Table 1 exemplifies management standards for the concentration of harmful substances in the air in museum rooms. In this standard, the concentration of each substance in the air is classified into five stages of ranks I to V, and it is recommended that acid gases (acetic acid and formic acid) are ranks I to II. That is, it is desirable that the concentration in the air of both acetic acid and formic acid is less than 200 μg / m ³ (less than 0.082 ppm).

  Conventionally, in order to measure the concentration of such a very small amount of acid gas, it is common to use a precision method involving chemical analysis. This precision method is a method in which the air to be measured is sampled for a long time and then taken back to the laboratory, where it is analyzed and quantified with a chemical analyzer (ion chromatography). Sampling sucks the air to be measured in ultrapure water and dissolves and collects the target acidic substance. However, since it is extremely small, it usually takes 2 to 24 hours to increase the sensitivity. . In addition, it is necessary to perform chemical analysis of the ultrapure water sample brought back and calculate the concentration in the air based on the analysis result. For this reason, in the measurement by the precision method, it usually takes several weeks to obtain the result from the measurement preparation. In addition, sampling and analysis operations require specialized chemical knowledge, and measurement costs are high. Therefore, it is difficult for the person in charge at the site / facility to easily perform concentration measurement by a precision method at an arbitrary timing.

On the other hand, a method using a gas detection tube is widely used as a method for easily knowing the concentration of a specific gas present in the air. The gas detector tube is a transparent tube such as a glass tube in which a detector that reacts with a specific gas and changes color is charged. By flowing a certain amount of air to be measured in this tube and reading the length of the region where the detection agent changes color (discoloration length), the discoloration length can be converted into the concentration of the specific gas in the air. It is. However, a detector tube capable of quantifying a small amount of acidic gas having an air concentration of less than 200 μg / m ³ has not been put into practical use. For example, as an existing acid gas detector tube, manufactured by Komyo Chemical Co., Ltd .; Model 216S is known. The measurable range of this type is that the concentration of acetic acid and formic acid in the air is 1 to 50 ppm (2452 to 122620 μg / m ^3). ).

JP 2005-345280 A JP 2004-85525 A

As described above, in order to manage the concentration of acid gas in a room such as a museum, it is necessary to detect acid gas of less than 200 μg / m ³ . In addition, in order to evaluate the acid gas release characteristics of building materials, it is desired to adopt a measurement method capable of detecting an acid gas concentration of less than 200 μg / m ³ . However, in order to quantify such a small amount of acid gas, it is currently necessary to rely on a precision method.
In view of such a current situation, the present invention intends to provide a technique that can easily measure the concentration of an extremely small amount of acidic gas in the air in a shorter time and at a lower cost.

As a result of detailed studies, the inventors have found that the above object can be achieved by a new and improved gas detector tube.
That is, in the present invention, a part containing a detection reagent that changes color by reacting with a specific gas (hereinafter referred to as “detection agent”) is loaded in a portion where the inner diameter of the tube is constant, and a certain amount of the object to be measured In the gas detection tube adapted to detect the concentration of the specific gas in the air by visually recognizing the color change length of the detection agent when air is passed in one direction in the tube,
The detection reagent is composed of an alkali that changes color by reacting with acetic acid or formic acid and a pH indicator.
The detection agent is a granule in which the detection reagent is coated on the surface of base particles (for example, silica sand particles) having an average particle size of 250 to 350 μm,
Discoloration length when air to be measured containing 10-1200 μg / m ³ acetic acid or formic acid in terms of air concentration at 25 ° C. is continuously vented through the pipe at a flow rate of 100-400 mL / min for a total of 5 L or more. An acid gas detector tube is provided in which the length is in the range of 2 to 80 mm. Here, the acidic gas to be detected is acetic acid or formic acid (the same applies hereinafter).

What uses sodium metasilicate as an alkali of a detection reagent is mentioned.
Examples include those in which cresol red is used as the pH indicator of the detection reagent.
As the detection agent, in particular, a base particle (for example, silica sand particle) having an average particle diameter of 250 to 350 μm having a hydrophobic layer formed on the surface thereof is preferably a granule in which the detection reagent is coated on the hydrophobic layer. It becomes.

The acid gas detection tube of the present invention is preferably a target in which particles containing a substance that collects NO ₂ (hereinafter referred to as “NO ₂ collection agent”) are loaded before the detection agent in the tube. It becomes. Examples of the substance that collects NO ₂ include those containing at least one of diphenylamine, 3,3′-dimethylbenzidine, and 3,3′-dimethylnaphthidine as components.

  In the present invention, the acid gas detector tube is used to detect the concentration of acid gas existing in the building room in the air a plurality of times at different times, so that the acid gas concentration in the room over time can be detected over time. A room air quality monitoring method for monitoring changes is provided.

  Furthermore, in this invention, the air in the container which put the building material sample is extract | collected continuously, it ventilates in the acidic gas detection tube in any one of Claims 1-6, and in the collection | recovery air using the detection tube A construction material quality evaluation method for evaluating the amount of acid gas released from building materials by detecting the acid gas concentration is provided.

When the acidic gas detection tube of the present invention is used, it is possible to know the concentration of a small amount of acidic gas in the air of less than 200 μg / m ³ . Compared with conventional precision methods, it can be measured very quickly and easily. Since no special chemical knowledge is required, the person in charge at the construction site, art museum or museum can freely select the time and place where the concentration is to be measured and perform the measurement work by himself / herself. For this reason, it becomes easy to grasp the change in the indoor acid gas concentration with time, and when the concentration increases, it is possible to take quick measures. It is also effective for concentration management during construction of museums, and for selecting materials that emit less acid gas.

In addition to the above, the present invention is expected to be applied in the following situations, for example.
-Judgment of the effect of acid gas on the display of important cultural properties-Grasping acid gas concentration when semiconductors, flat panel displays and other electronic products deteriorate-Judgment of production line start / stop at semiconductor manufacturing factories-Installation in clean rooms Of the life of a chemical filter

FIG. 1 schematically illustrates the configuration of the acid gas detection tube of the present invention.
This detection tube is loaded with a detection agent 2 containing a detection reagent in a portion having a constant inner diameter of a transparent tube 1 having a portion where the inner diameter of the tube is constant. The air to be measured passes through the pipe in one direction indicated by an arrow. The NO ₂ trapping agent 3 containing a substance that traps NO ₂ is preferably loaded before the detection agent 2. Protective materials 4 and 4 'are loaded between and behind these particles, and the particles flow through a spherical plug 5 made of, for example, a fluororesin on the front side and a stopper 6 made of a porous body on the back side. It is restrained not to do. Both ends of the transparent tube 1 are sealed at the time of manufacture of the detection tube, and are in a sealed state before use.

At the time of use, both ends of the transparent tube are broken at the broken lines 11 and 12 to form the measured air suction port 21 and the suction pump connection port 22. Then, the suction pump connection port 22 is connected to the suction pump, and the measured air is sucked from the measured air suction port 21 so that the inside of the transparent tube 1 is ventilated. When acidic gas (acetic acid or formic acid) is present in the air to be measured, it reacts with the detection reagent when passing through the gaps between the particles of the detection agent 2, and the detection reagent in the reacted portion changes color. The concentration of acid gas in the air is detected based on the discoloration length when a certain amount of air is ventilated. A scale 7 for reading the acid gas concentration is attached to the surface of the transparent tube 1 as necessary.
Hereinafter, matters for specifying the present invention will be described.

[Detection reagent]
The detection reagent contains an alkali that reacts with acetic acid or formic acid and a pH indicator as components. That is, the principle that acetic acid or formic acid reacts with an alkali and a pH indicator is colored is used. It is desirable to use a pH indicator having a color change range near neutrality. For example, cresol red is suitable. Cresol red turns yellow near neutrality. The coloration principle in this case can be schematically shown as follows:
CH ₃ COOH (acetic acid) or HCOOH (formic acid) + Alkali + pH Indicator → Yellow reaction product

Various alkalis can be used, and examples thereof include sodium metasilicate. In this case, for example, the reaction with acetic acid is as follows.
2CH ₃ COOH + Na ₂ SiO ₃ → 2CH ₃ COONa + SiO ₂ + H ₂ O
At this time, if the pH indicator is cresol red, the detection reagent turns from pale pink to light yellow.

[Detection agent]
In the case of a conventional general acid gas detection tube, the amount of air to be measured that allows the detection agent to pass through the gap is as small as 1 L or less (for example, 200 mL). However, in the present invention, since it is necessary to detect an extremely small amount of acidic gas in the air, a total of 5 L or more of air is continuously passed through the gap between the detection agents as described later. As a result of various investigations in consideration of such a situation, it has become clear that it is preferable to use a granule in which the surface of a base particle having an average particle size of 250 to 350 μm is coated with the detection reagent as a detection agent. . More preferably, the BET specific surface area is 0.05 to 0.1 m ² / g.

  In particular, when the crushed silica sand is classified and the average particle diameter is adjusted to 250 to 350 μm as the base particle of the detection agent, the air is well dispersed in the gap between the detection agent particles loaded in the tube. However, it is possible to effectively avoid the phenomenon that the air flow is short-circuited or drifted in the particles.

  Moreover, it is preferable to use the base particles having a hydrophobic layer formed on the surface. When the detection reagent is coated on the surface of the base particle on which the hydrophobic layer is formed, the detection sensitivity is improved for highly hydrophilic organic acids. Moreover, the influence of humidity during measurement is reduced. The hydrophobic layer can be formed, for example, by coating the surface of the base particles with colloidal silica dispersed in an organic solvent.

  When the average particle diameter of the substrate particles is larger than 350 μm, the reaction density is coarse and the boundary of discoloration tends to be unclear, making it difficult to accurately read the discoloration length. On the other hand, when the average particle diameter of the base particles is less than 250 μm, the color change boundary becomes clear, but the sensitivity is lowered, and it may be difficult to detect an extremely small amount of acidic gas.

[Target air to be measured]
The air to be measured containing 10 to 1200 μg / m ³ of acetic acid or formic acid in terms of the concentration in air at 25 ° C. is the measurement target. To monitor changes in the indoor environment of such museums, it is necessary that the concentration in the air to detect the 10 [mu] g / m ³ or more ~200μg / m ³ of less than trace amounts of acid gases. Moreover, this level of sensitivity is also required in order to understand the acid gas release characteristics of building materials. On the other hand, changes over time and the indoor environment during building construction, in order to grasp the temporal change of the indoor environment of museums is to cope also 200 [mu] g / m ³ or more ~1200μg / m ³ range of concentrations It is desirable. Therefore, the acidic gas detection tube of the present invention is intended to cover a wide concentration range of 10 to 1200 μg / m ³ . As a result of many experiments, it has been confirmed that formic acid can be quantified by converting the concentration scale printed on the detector tube. In the case of air to be measured containing both acetic acid and formic acid, the quantitative value can be read as the total amount of acetic acid and formic acid (ppm or μg / m ³ ).

[Discoloration length and air flow]
The detection tube of the present invention has a discoloration length of 2 to 2 at an acidic gas concentration of 10 to 1200 μg / m ³ when the air to be measured is continuously vented through the tube at a flow rate of 100 to 400 mL / min for a total of 5 L or more. It has characteristics that can be in the range of 80 mm. When the discoloration length is less than 2 mm, accurate quantification is difficult. On the other hand, if the discoloration length is excessively long, it does not lead to improvement in measurement accuracy, and the amount of air to be measured increases, which is uneconomical. As a result of various studies, it is possible to quantify sufficiently accurately within a range where the discoloration length is within 80 mm.

If the concentration of the acid gas is the same, the discoloration length becomes longer as the total aeration amount is increased. However, in order to enable accurate quantification in the acidic gas concentration range of 10 to 1200 μg / m ³ , it is necessary to secure an air flow of 5 L (liters) or more in the sample loaded with the detection agent. If the air flow rate is smaller than that, acetic acid or formic acid is slightly trapped before the detection agent, and the measurement accuracy tends to be lowered. However, it is sufficient to adjust the total ventilation amount within a range of 20 L or less.

  In addition, the gas flow rate (flow velocity) must be 100 mL / min or more, and it is necessary to continuously vent until the measurement is completed. When the flow rate is less than 100 mL / min, or when ventilation is stopped in the middle, the measurement accuracy is liable to decrease, which is not preferable. The continuous ventilation time is desirably 15 minutes or longer, and more preferably 30 minutes or longer. It is difficult to obtain high measurement accuracy with a very short ventilation.

  Regarding the discoloration length, basic characteristics are determined by the coating amount of the detection reagent. In addition, the discoloration length can be adjusted to be within a range of 80 mm or less depending on the total ventilation amount at the time of use. Specifically, for a detection tube manufactured with a certain coating amount, for example, a calibration curve for a total ventilation amount of 6L and a calibration curve for 12L are obtained in advance, and ultra-high sensitivity when the acid gas concentration is extremely small. For the detection, the total ventilation rate is 12L, and when 12L is over the range (for example, when the discoloration length exceeds 80 mm), the total ventilation rate is 6L.

[NO ₂ collector]
According to the detailed examination by the inventors, unlike the case of the conventional acid gas detector tube in which the total ventilation rate of the air to be measured is 1 L or less (for example, about 200 mL), the total ventilation rate is 5 L or more. In order to achieve highly accurate quantitative determination, it has been found that it is very effective to interpose a NO ₂ trapping agent before the detection agent in the tube. That is, when 0.02 ppm or more of NO ₂ gas coexists in the air to be measured, the color change boundary of the detection reagent becomes unclear, and the scale indication of the detection tube is larger than the actual acid gas concentration (color change length). Tends to be longer).

The NO ₂ concentration of 0.03 ppm is the concentration level of NO ₂ present in normal air. It is necessary to ventilate a large amount of air to be measured by using a detector tube with a filter that can remove 0.02 to 0.06 ppm of NO ₂ , which is set as an environmental standard, in front of the detector. The acid gas detector tube of the invention is very preferable.

As the NO ₂ trapping agent, a material obtained by coating a surface of base particles having an average particle diameter of 250 to 350 μm with a substance that traps NO ₂ can be suitably used. By using the base particles having such a particle size, the air passing through the tube is easily dispersed between the particles, and the efficiency of collecting the NO ₂ gas component is increased. As the substrate, those obtained by classifying crushed quartz sand and adjusting the average particle size to 250 to 350 μm can be suitably used.

Examples of the substance that collects NO ₂ include those containing at least one compound of diphenylamine, 3,3′-dimethylbenzidine, and 3,3′-dimethylnaphthidine as a component. These compounds trapping NO ₂ gas component in the air by reaction with NO _2. Acid gas components (acetic acid, formic acid) pass through without reacting.

[Monitoring indoor air quality]
By using the gas detection tube of the present invention, it is possible to monitor a change in air quality over time in a building room such as an art museum or a museum that dislikes acid gas. Specifically, the acid gas detector tube of the present invention is used to detect the concentration of acid gas present in the building room in the air regularly or irregularly multiple times at different times. It is possible to grasp the change with time of the concentration of acid gas in the air. What is necessary is just to set the space | interval of a measurement according to each indoor environment and the measurement objective. Unlike the precision method, the concentration of the acid gas in the air can be detected quickly on the spot. For example, if the measurement interval is set to several hours, it is possible to know the temporal change in the air quality of the day.

[Evaluation of building material quality]
As another use mode of the gas detector tube of the present invention, there is a use for evaluating how much acid gas a certain building material emits. In this case, after the building material to be evaluated is left in the closed space for a certain period of time, the acid gas released from the building material by detecting the concentration in the air of the acid gas present in the closed space using the acid gas detector tube of the present invention. The amount can be evaluated. Thereby, it is also possible to quickly determine whether the building material can be applied to a specific building.

[Verification test with acid standard gas]
A detector tube having the configuration shown in FIG. 1 was produced. The transparent tube 1 is a glass tube conventionally used for a general detection tube, and the inner diameter of the tube is 3.5 to 3.7 mm. The detection reagent used sodium metasilicate as an alkali component and cresol red as a pH indicator. Silica sand having an average particle size of 250 to 350 μm, which was crushed and classified, was used as the base particles of the detection agent 2. A hydrophobic layer was formed on the surface of the silica sand particles by coating the surface of the base particles with colloidal silica dispersed in an organic solvent. The surface of the silica sand particles (on the hydrophobic layer) was coated with a detection reagent. Based on the results of various preliminary experiments, the coating amount is 30 mm when the air with an acetic acid concentration of 200 μg / m ³ is aerated at a flow rate of 200 mL / min and a total aeration amount of 12 L. Set as a goal. The loading length of the detection agent 2 was 80 mm. The NO ₂ scavenger 3 was loaded at a loading length of 15 mm before the detection agent 2. The base particles of the NO ₂ collection agent 3 were crushed and classified into silica sand having an average particle size of 250 to 350 μm, and diphenylamine was coated on the surface of the base as a substance for collecting NO ₂ . The coating method was the same as that of the detection reagent described above, and the coating amount was set so that a filter capable of removing 0.02 ppm of NO ₂ at the loading length was constructed. For the protective material 4, silica sand having a classified average particle diameter of 250 to 350 μm was used, and for 4 ′, synthetic zeolite was used. The front spherical plug 5 is made of Teflon (registered trademark), and the rear stopper 6 is a cotton plug.

  Using this acid tube calibrated to various acetic acid concentrations by the permeation tube method, the discoloration length was measured when vented at 25 ° C, flow rate 200 mL / min, total air flow 6 L and 12 L, and acetic acid concentration A calibration curve indicating the relationship between the color change length and the color change was obtained. A suction pump having a function of controlling the flow rate (flow velocity) to a constant value and a function of automatically stopping suction when a predetermined total ventilation amount (6 L or 12 L) is used was used.

FIG. 2 illustrates a plot of measurement results and a calibration curve. As can be seen from FIG. 2, it was confirmed that this detector tube can detect the acetic acid with high accuracy in the air concentration range of 10 to 1200 μg / m ³ . By selecting the total air flow rate, the discoloration length in the above density range falls within the range of 2 to 50 mm, which is sufficiently practical. When detecting a very small amount of acid gas having an acid gas concentration of less than 200 μg / m ^3, it is advantageous to increase the total ventilation rate in order to improve measurement accuracy. Even when a 12 L calibration curve is used in the above example, the sampling time is 1 hour, which is very short compared to the precision method.

[Verification of temperature and humidity effects]
About the detector tube produced in Example 1, the influence of the temperature and humidity on discoloration length was investigated by the acidic gas of 5 degreeC, 20 degreeC, and 35 degreeC calibrated to the various acetic acid concentration by the permeation tube method. The flow rate was 200 mL / min, and the total aeration rate was 12 L. FIG. 3 illustrates the influence of temperature when the humidity is fixed at 50% RH. FIG. 4 shows the influence of humidity when the acetic acid concentration is 370 μg / m ³ .

  Regarding the temperature, there was a tendency that the indicated value was lower as the temperature was lower and the indicated value was higher as the temperature was higher (FIG. 3). On the other hand, it was confirmed that there was no significant variation in humidity within the range of 20 to 80% RH (FIG. 5). In general, in museums and museums, the humidity is controlled to about 40 to 60% RH by air-conditioning equipment to protect the exhibits, so the effect of humidity on the measured value is not considered to be a problem in normal use. . Therefore, it is possible to measure with high accuracy by setting the applicable humidity range as, for example, 20 to 80% RH as the product specification and correcting the indicated value according to the temperature of the air to be measured. As a method for simple correction based on temperature in the field, for example, there is a method of providing a table showing the relationship between acid gas concentration and discoloration length at each temperature attached to the detector tube product, and several temperature levels. It is effective to attach a scale on the detector tube so that the scale position at the actual temperature can be found by proportional distribution.

[Measurement of acid gas concentration in the museum]
A scale for displaying the acid gas concentration at 25 ° C. in the case of a flow rate of 200 mL / min and a total air flow of 12 L was attached to the acid gas detector tube produced in Example 1 based on the calibration curve shown in FIG. Using this detector tube, acid gas concentrations were measured at various locations in the museum. At that time, the temperature of the air to be measured was measured, and the value of the acid gas concentration converted to 25 ° C. was obtained from the value of the acid gas concentration obtained by performing the temperature correction based on the result of Example 2. At the same time, the air for use in the analysis by the precision method was sampled and brought back to the laboratory to obtain the acid gas concentration in terms of 25 ° C. by ion chromatography.

FIG. 5 shows the correspondence between the measurement result obtained by the acid gas detector tube and the measurement result obtained by the precision method. Although there was some variation, a good correlation (correlation coefficient = 0.96) was observed between the measured values. That is, according to the acid gas detector tube of the present invention, it is possible to rapidly monitor the time course of the traces of the concentration of acid gases such as 10 [mu] g / m ³ or more ~200μg / m less than ^3.
In addition to the acidic gas, alkaline gas and organic gas are mixed in the field air, but it was also confirmed that the presence of these gases does not affect the indication of the detector tube.

[Evaluation of building material quality]
As shown in FIG. 6, the building material sample was put in a stainless steel 20L container, and the air in the container was continuously collected while air was introduced from the outside at a flow rate of 0.5L / min. The tube was aerated at a flow rate of 0.2 L / min for 1 hour. The building material sample in the container is placed at a position to be an air flow path. On the other hand, the same building material sample was aerated for 24 hours as shown in FIG. 7 to collect gas components from the air in the container, and analyzed by a precision method. Such a test was carried out on various building material samples, and the correspondence between the detector tube method of the present invention and the precision method was examined for the amount of acid gas released from the unit surface area of the building material sample per unit time. The results are shown in FIG.

  As can be seen from FIG. 8, there is a good correlation (correlation coefficient = 0.97) between the measurement values of the detection tube method and the precision method of the present invention, and the quality of building materials can be quickly increased by using the detection tube of the present invention. It was confirmed that it is possible to evaluate.

The figure which illustrated typically the composition of the gas detection pipe of the present invention. The graph which illustrated the relationship between acidic gas (acetic acid) density | concentration and discoloration length about the detection tube of this invention. The graph which illustrated the influence of the temperature which acts on discoloration length about the detection tube of this invention. The graph which illustrated the influence of the humidity which acts on acidic gas concentration (detection pipe instruction value) about the detection pipe of this invention. The graph which illustrated the correspondence of the measurement result by the detection tube of this invention, and the measurement result by a precision method about the acidic gas density | concentration in indoor air. The figure which illustrated typically the test method which evaluates building material quality using the detector tube of this invention. The figure which illustrated typically the test method which evaluates building material quality by a precision method. The graph which illustrated the correspondence of the measurement result by the detection tube of the present invention, and the measurement result by a precision method about acid gas emitted from building materials.

Explanation of symbols

1 transparent tube 2 detector agent 3 NO ₂ scavenger 4,4 'protectant 5 spherical plug 6 stopcock 7 scale 21 to be measured air inlet 22 suction pump connection port

Claims (8)

Particles containing a detection reagent that changes color by reacting with a specific gas (hereinafter referred to as “detection agent”) are loaded into the part where the inner diameter of the tube is constant, and a certain amount of air to be measured is directed in one direction into the tube. In the gas detection tube adapted to detect the concentration of the specific gas in the air by visually recognizing the discoloration length of the detection agent when aerated.
The detection reagent is composed of an alkali that changes color by reacting with acetic acid or formic acid and a pH indicator.
The detection agent is a granule in which the detection reagent is coated on the surface of a base particle having an average particle diameter of 250 to 350 μm,
Discoloration length when air to be measured containing 10-1200 μg / m ³ acetic acid or formic acid in terms of air concentration at 25 ° C. is continuously vented through the pipe at a flow rate of 100-400 mL / min for a total of 5 L or more. An acetic acid or formic acid detector tube, wherein the length is in the range of 2 to 80 mm. The acetic acid or formic acid detector tube according to claim 1, wherein sodium metasilicate is used as an alkali of the detection reagent. The acetic acid or formic acid detection tube according to claim 1 or 2, wherein cresol red is used as a pH indicator of the detection reagent. The acetic acid according to any one of claims 1 to 3, wherein the detection agent is a granule of base particles having an average particle diameter of 250 to 350 µm having a hydrophobic layer formed on the surface, and the detection reagent is coated on the hydrophobic layer. Or formic acid detector tube. The acetic acid or formic acid according to any one of claims 1 to 4, which is loaded with granules (hereinafter referred to as "NO ₂ trapping agent") containing a substance that traps NO ₂ before the detection agent in the tube. Detector tube. The acetic acid or formic acid detector tube according to claim 5, wherein the substance that collects NO ₂ contains at least one of diphenylamine, 3,3'-dimethylbenzidine, and 3,3'-dimethylnaphthidine as a component. By using the acetic acid or formic acid detector tube according to any one of claims 1 to 6 to detect the concentration in the air of the acidic gas present in the building room a plurality of times at different times, acetic acid or formic acid in the room A method for monitoring indoor air quality, which monitors changes in air concentration over time. The air in the container containing the building material sample is continuously collected and ventilated in the acetic acid or formic acid detector tube according to any one of claims 1 to 6, and the acetic acid or formic acid in the sampling air is collected using the detector tube . A construction material quality evaluation method that evaluates the amount of acid gas released from building materials by detecting the concentration.

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