Effects of Indoor Environment on Mold Growth Mechanism Based on a Multivariate Experimental System
学生名:楊 智君
研究テーマ:Effects of Indoor Environment on Mold Growth Mechanism Based on a Multivariate Experimental System
(多変量実験に基づく室内環境がカビの成長メカニズムに与える影響に関する研究)
入学年月:2021.10
修了年月:2025.03
取得学位:博士（工学）
論文概要:Indoor environments are where people spend most of their daily lives, and their quality directly impacts health and comfort. Comprising various factors interact to determine the livability of a space. However, poor control of indoor conditions can lead to the accumulation of contaminants, among which mold contamination is one of the most common and hazardous. Molds are a type of fungi that are widely present in nature, typically thriving in damp, warm, poorly ventilated environments. When indoor air humidity exceeds 60%, molds proliferate rapidly, releasing spores that disperse into the air. Areas prone to dampness are especially susceptible to mold contamination. Mold not only compromises building structure but also poses health risks to occupants.
This study focuses on the issue of mold contamination in indoor environments. To address this problem, we conducted an investigation and developed a multifactorial mold growth laboratory. Through our survey, we identified the current state of indoor mold contamination in the area and the primary mold species responsible for it. Laboratory research allowed us to analyze in depth the environmental factors influencing indoor mold growth. Our findings aim to support future prevention and control efforts for mold contamination in Guangzhou and similar regions.
Chapter 1, Research Background and Purpose of the Study, introduces the concept of the indoor environment in buildings and the critical microbial threats present within. The design of indoor spaces directly affects the health of life of occupants. One of the most significant yet often overlooked impacts on occupant health comes from indoor microorganisms. The relationship between the indoor environment and microorganisms is bidirectional. To reduce the impact of indoor microorganisms and prevent the growth and spread of harmful species, effective indoor microbial management is essential. This chapter provides an overview of the study’s structure and summarizes the content of each subsequent chapter. This study seeks to enhance our understanding of the interaction between indoor environmental conditions and microorganisms, aiming to inform strategies for improved indoor environmental quality.
Chapter 2, Literature Review of Indoor Mold, aims to introduce current research on indoor mold and its control. Indoor mold has significant implications for occupant health. Mold is associated with various diseases, and in China, especially in the southern regions, respiratory conditions highlighting the urgent need for improvement. The study also reviews existing approaches to mold control in indoor environments. Predictive measures during construction, combined with maintenance, management, and remediation strategies during building use, are employed to suppress indoor mold contamination. Governments worldwide have established standards to reduce mold contamination in buildings. However, there remains limited knowledge of mold contamination in southern China, and research on mold growth under the combined influence of multiple environmental factors is sparse. This study seeks to improve understanding of mold contamination in Guangzhou, China, and to conduct experimental research on mold growth under multifactorial conditions relevant to this region.
Chapter 3, Multi Factor Laboratory Research Method based on Field Research, outlines the study’s subjects and primary research methods. First, the basic information on Guangzhou, China, the region selected for this study, is presented. Next, the study’s methodology is described.
Chapter 4, Field Research and Analysis of Typical Case in Guangzhou Area, presents the results of the questionnaire survey and case investigations conducted in the Guangzhou area. Among the 729 valid responses collected through the online survey, only 22% reported no signs of mold contamination in their homes. The survey results indicate a strong correlation between high indoor mold contamination and factors. Based on the survey findings, typical cases were selected for in-depth field investigations. Temperature and humidity variations in these rooms were recorded, and both wall and air mold samples were collected. Results showed that the ceiling contained areas of high humidity, which corresponded to the most severe mold contamination. Mold sampling revealed that the primary mold species contributing to contamination in these cases were Trichoderma, Penicillium, and Aspergillus.
Chapter 5, Design and Verification of Multi Tactor Experimental System. To replicate the complex indoor environment, we designed a novel experimental system. Based on the Fluent simulation of a model room, we created a test box capable of accurately simulating real ventilation conditions. In collaboration with the Guangdong Provincial Academy of Building Research Group Co., Ltd., we utilized their air enthalpy difference laboratory to construct a mold growth experimental system. Finally, we conducted validation experiments, which confirmed that our system effectively supports normal mold growth.
Chapter 6, The Relationship Between Temperature, Humidity, Ventilation and Indoor Mold Growth. A total of seven experiments were conducted. Based on the observed mold growth rates, we found that mold growth was slow at both low (24°C) and high (32°C) temperatures. Under low humidity conditions (50% RH), mold growth was suppressed. Additionally, the study revealed that higher inlet wind speeds in the test box also promoted faster mold growth. This stimulative effect of inlet wind speed on mold growth was consistent across various temperature and humidity conditions. The position of materials within the box also influenced mold growth; mold growth was more vigorous on materials placed in elevated positions.
Chapter 7, The Relationship Between Light Exposure and Indoor Mold Growth. Custom light-shielding panels were designed with transparency ratios ranging from 10% to 90% to adjust the light intensity within the test box. A full-spectrum supplementary light was placed outside the transparent panel to mimic natural sunlight exposure. Using a controlled variable method, five experiments were conducted. Results indicated that when the box’s transparency ratio was set to 10%, mold growth rates were higher compared to both fully opaque and other transparency ratios. When the transparency ratio was increased to 20% or more, mold growth rates dropped below those observed in fully opaque conditions. For transparency ratios above 50%, the inhibitory effect on mold growth was consistent, and this suppression effect was stronger than the growth-promoting influence of increased wind speed.
Chapter 8, Conclusion and Prospect. The main conclusions of this study and the prospects for future research are summarized.