Effective strategies for indoor particulate air pollution control

Ph.D.It is crucial to reduce indoor exposure to particulate air pollution of indoor and outdoor origin, which is a dominant risk factor to damage occupants’ health. This thesis aims to explore the effective strategies for controlling indoor exposure to particulate air pollution in residential buildings with natural ventilation.This study firstly used the time-resolved indoor and outdoor PM₂.₅ (particulate matter with aerodynamic equivalent diameter less than 2.5 μm) concentrations and the window opening/closing behavior to differentiate the indoor exposure to PM₂.₅ of indoor and outdoor origin for naturally ventilated buildings. A statistical algorithm of change point analysis, the physical mechanism of PM₂.₅ mass balance and window behavior characteristics were combined to process the data and recognize the indoor PM₂.₅ sources. To verify the method, a set of experiments were conducted in a small-scale test rig.Besides, this study then applied the differentiation method to real building case for further validation. The real-time indoor PM₂.₅ concentrations and windows behavior in an apartment located in Tianjin, China, were monitored for a whole year. The indoor emissions and their contributions to the total exposure to PM₂.₅ were analyzed in the apartment.With the indoor emissions being correctly identified, people can take effective strategies to control indoor exposure to PM₂.₅ of both indoor and outdoor origin. An opening window can introduce fresh air and dilute indoor emissions. Besides, air filtration technology can be used to further reduce indoor exposure to particulate air pollution. Therefore, this study systematically reviewed nanofiber filter media in the literature. It was found that nanofiber filters have a relatively low pressure drop and high particle removal efficiency compared with conventional fibrous filters.Coating nanofiber filter on window screen could provide clean fresh air in the naturally ventilated residence. This study fabricated nanofiber window screens and measured the PM₂.₅ removal efficiency and pressure drop under various window opening angles. The measured data validated the proposed model for predicting the pressure drop. Then, the modelling results of a natural ventilation case showed that the nanofiber window screen can reduce indoor PM₂.₅ of outdoor origin and the ventilation rate was improved when compared with infiltration only.To facility the usage of nanofiber filter media, this study experimentally developed a semi-empirical model between the pressure drop and solid particle loading mass for nanofiber filters under various face velocities. Then the assessment of the long-term performance indicated that of an air cleaner equipped with a nanofiber filter could effectively control indoor PM₂.₅, but the lifetime of the nanofiber filter was shorter than that of traditional HEPA filters.Apart from solid particles, PM₂.₅ contains amounts of liquid aerosols. Thus, this study investigated the long-term filtration performance by conducting experiments to understand the evolution of wetting liquid aerosols, taking incense particles as an example, on nanofiber filter media and the influence of loading mass on PM₂.₅ removal efficiency and pressure drop. Using the experimental data, the method for establishing empirical equations for pressure drop and PM₂.₅ removal efficiency in terms of loading mass were developed.減少室內暴露於室內和室外空氣中的微粒污染至關重要，這是損害人體健康的主要風險因素。本論文旨在探索有效的策略，用以控制自然通風住宅中的顆粒污染物室内暴露量。本論文首先使用室內和室外PM₂.₅（空气动力学当量直徑小於2.5 μm的顆粒物）濃度和窗戶的開/關行為，來解析自然通風下的室內暴露於室內发生的和室外渗入的PM₂.₅。結合了轉變點分析的統計方法，PM₂.₅質量平衡的物理模型和开窗行為來識別室內PM₂.₅散發源。並且進行了系統的實驗驗證該方法。此外，本論文將該方法應用於實際建築以進一步驗證。對位於中國天津的一間公寓室內PM₂.₅濃度和窗戶行為進行整年實時監測。分析了公寓中室內发生源對室內PM₂.₅總暴露量的貢獻。通過正確識別室內PM₂.₅散發源，人們可以採取有效策略來控制室內PM₂.₅。在此基礎上，空氣過濾技術可用於進一步減少室內顆粒污染物的暴露程度。首先，本研究系統地回顧了文獻中的納米纖維濾料。發現與常規纖維過濾器相比，納米纖維過濾器具有相對較低的壓降和較高的PM₂.₅去除效率。把納米薄膜塗在窗紗上可為自然通風的住所提供乾淨的新鮮空氣。本論文製造了納米纖維窗紗，並測量了在不同窗戶打開角度下的PM₂.₅去除效率和壓降。實測數據驗證了所提出的預測壓降的模型。然後，自然通風案例的模擬結果表明，納米纖維窗紗可以有效地減少室外的室內PM₂.₅，並且與僅滲透（所有窗戶關閉）相比，通風量得到了提高。為了落實納米纖維過濾器的使用，本研究通過實測建立了與面風速相關的納米纖維過濾器的壓降與固體顆粒負載質量的半經驗模型。對配備納米纖維過濾器的空氣淨化器的長期性能的表明它可以有效地控制室內PM₂.₅，但是納米纖維過濾器的壽命比傳統的HEPA過濾器短。除固體顆粒外，PM₂.₅還包含一定量的液態氣溶膠。因此，本研究通過實驗以了解親水的液態氣溶膠的演變（以熏香液態顆粒為例）對納米纖維濾料的影響及負載質量對PM₂.₅去除效率和壓降的影響。利用實驗數據，本論文提出了建立壓降和PM₂.₅去除效率隨負載質量變化的經驗方程的方法。Xia, Tongling.Thesis Ph.D. Chinese University of Hong Kong 2021.Includes bibliographical references (leaves 163-175).Abstracts also in Chinese.Title from PDF title page (viewed on April 1, 2022)