On using aroma to improve the workplace productivity with increasing their comfort, an intermittent exposure method is considered to be more effective than a continuous exposure method, which causes olfactory habituation. On the other hand, since there is concern about the effect of repeated exposure on olfactory fatigue, it is thought that it would be meaningful in the future to be able to evaluate the tendency of aroma intensity to decay with time in intermittent exposure with a numerical index. Using aroma intensity evaluations in intermittent and continuous exposure experiments using two aroma, two cases were examined: one in which the constant term of the regression curve was used as an index, and the other in which the area of the regression curve up to a arbitrary elapsed time was used as an index. With both indices, the aroma intensity evaluation in the intermittent exposure method was greater than that in the continuous exposure method, indicating that the intermittent exposure can maintain the aroma intensity for a longer time. In addition, the latter index was more convenient in that it could evaluate the cumulative aroma intensity up to an arbitrary time. Furthermore, using these indices, the spray concentration and spray interval set in the experiment were compared between conditions, and it was shown that the effect of the spray concentration on the index was relatively small, and that the longer the spray interval, the greater the index.

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In recent years, indoor air pollution caused by substitute materials for guideline VOCs, household products, and microbially derived VOCs has been observed. To assess health risks posed by such diverse VOCs, comprehensive and continuous monitoring of indoor chemical pollution is essential. In this study, sampling rates (SR) for 93 VOCs frequently detected in indoor air were calculated through exposure experiments using passive sampling. The experimentally determined SR shows high linearity (R² > 0.95) and reproducibility (RSD < 15%) for all target compounds. Validation in a simulated indoor environment showed that the deviation from SR obtained via the exposure chamber method was within 15%, indicating the applicability of these SR to actual indoor environments. A comparison between theoretical SR and experimental SR revealed significant discrepancies for low boiling point compounds. Further analysis of the relationship between molecular volume (volume3D) and SR identified molecular volume as a key factor contributing to the reduction of SR, particularly for chain hydrocarbons and cyclic siloxanes.

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Conventionally, simultaneous analysis of formaldehyde and other VOCs requires separate analytical systems (HPLC and GC/MS), leading to increased analytical labor and reduced efficiency. This study aims to develop a passive sampling method capable of simultaneously collecting and analyzing formaldehyde and other volatile organic compounds (VOCs) in indoor environments. To resolve this issue, we derivatized formaldehyde from o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) and applied GC/MS measurements to passive sampling. A mixture of PFBHA-impregnated silica gel and activated carbon was used as an adsorbent to stabilize the sampling rate (SR) under high humidity. The optimal adsorbent ratio was determined to be 300 mg:300 mg (activated carbon:silica gel), and the SR for each VOC was calculated through exposure testing. The results demonstrated high sampling rates of 0.115 and 0.247 L/min for toluene and formaldehyde, respectively. Moreover, the SR remained stable within a variation of ±15% across a humidity range of 10–80% RH and a temperature range of 15–35 °C, indicating minimal impact on quantification. This method enables simple and highly sensitive VOC monitoring and is a useful tool for indoor air quality monitoring.

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Sofas are known to be contaminated with mites, but no data exist on the amount of the mite allergen Der 1 detected in sofas in Japan. In October 2017, the authors collected house dust from sofas and floors in five homes in the Kanto region and measured the amount of Der 1 in the dust. The geometric mean of Der 1 in the sofa dust was 27.8 μg/g, and that in the floor dust was 2.6 μg/g. Four of the five sofas had Der 1 levels exceeding 10 μg/g dust, which is considered the threshold for an increased risk of asthma, while the remaining one exceeded 2 μg/g dust, which is considered the threshold for an increased risk of mite sensitization.

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In response to the need for effective infection risk mitigation in public transportation during infectious disease outbreaks and reduction of the exposure to particles in the atmospheric environment should be implemented, this study conducted experiments and field surveys to evaluate the effectiveness of medium-performance filters and their long-term performance degradation, particularly in reducing exposure to airborne particles. In laboratory experiments, three types of electrostatic filters were tested to assess changes in pressure drop and particle removal efficiency during extended indoor particle loading. Results showed a significant decline in removal efficiency from the early stages of use, primarily due to the loss of electrostatic charge. The removal efficiency, which was 79%, 48%, and 69% for filter A, B, and C at the start, decreased to 43%, 6.7%, and 21% after 73 days, respectively. In high-concentration particle loading tests, it was confirmed that larger particles were mainly captured through physical clogging, while electrostatic charge played a key role in collecting smaller particles. After discharging of the filter using isopropyl alcohol, the efficiency for small particles dropped markedly. Furthermore, in performance evaluations of filters installed in buses in actual operation, some vehicles maintained equivalent air change hour of approximately 20 /h even after two years of filter use, while others showed a decline to 10 /h after only six months of use. The performance changes of filters in buses showed a similar trend to those observed in indoor tests. These findings provide important insights into the aging behavior of medium-performance filters and inform design and maintenance strategies for vehicle HVAC systems.

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Compared to passenger cars, there have been fewer studies on the on-board environment of large buses and fewer studies on infection control and air quality. The analysis of odors emitted from the air conditioning equipment and atmosphere of large buses has been difficult because it requires multifaceted studies that include factors directly related to passenger safety, such as micro-organisms and aerosols. This study describes the process and results of evaluating the odor of air collected from the air conditioning vents of buses using sensory evaluation and instrumental analysis. Odor sensory test and instrumental analysis combining odor-sniffing gas chromatograph: thermal desorption (TD), gas chromatograph time-of-flight mass spectrometer (GC-TOFMS) and sniffing with odor intensity device (OID) were used. The results showed that sniffing inside the bus was unsuitable for sensory evaluation due to the large influence of the panel's body odor, and that this influence could be reduced by collecting odor samples in a bag and sniffing them outside the bus. We then found odor substances that were thought to emanate from human body and bus interior materials by sniffing ourselves with OID. As a result, this screening method with TD-GC-OID-TOFMS enabled the detection and estimation of the substances and sources that have an impact on the odor inside of buses.

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Vehicle cabin air contains various chemical substances from interior materials, personal belongings, and combustion gases, raising concerns about potential health risks. Conventional target analyses are limited to specific compounds and are insufficient for comprehensive risk assessment. In this study, we developed a risk screening approach by combining quantitative non-targeted analysis (qNTA)—which integrates thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) with post-column reaction-flame ionization detection (PR-FID)—with in silico toxicity prediction. This method enables simultaneous qualitative and quantitative evaluation without standard analytical reagents by integrating structural information from MS with methane-equivalent concentrations obtained via FID, and can be applied to unknown substances. Using the proposed approach, approximately 130 chemical substances were identified and quantified in the cabin air of trucks, with Hexane (track A: 550* μg m⁻³, track B: 710 μg m⁻³) (* indicates reference values) and Ethyl acetate (track A: 560* μg m⁻³, track B: 44 μg m⁻³) detected at relatively high concentrations. Furthermore, risk potentials (MOE_p) were calculated based on predicted no-observed-effect levels (NOEL_p) from in silico toxicity prediction and estimated human exposure rates. As a result, Hexane (MOE_p = track A: 490, track B: 370) and Butylcyclohexane (MOE_p = track A: 2,700, track B: 1,900) were identified as compounds with high-risk potential.

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[in Japanese]

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Visualization of vehicle cabin air quality is being promoted for the purpose of providing safe and secure air and monitoring appropriate air quality control. Air quality visualization necessitates continuous monitoring of chemical compounds using gas sensors. However, information on the fundamental performance and usage of gas sensors is insufficient. In this study, fundamental investigations were carried out to establish a standard evaluation method for gas sensors. This paper presents a comprehensive study on the GC-MS analysis of silicone compounds derived from gas tubes and volatile organic compounds presented in indoor air, which affect the response signal of gas sensors. In addition, this report will be presented on the construction of a water vapor generation system for precise humidity control.

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