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研究生:郭韋志
研究生(外文):Wei-Chih Kuo
論文名稱:定性密合度測試微粒粒徑分布需求
論文名稱(外文):Searching for the Optimal Challenge Aerosol Size Distribution for QLFT
指導教授:陳志傑陳志傑引用關係
指導教授(外文):Chih-Chieh Chen
口試委員:蔡朋枝陳振菶李書安
口試委員(外文):Peng-Chi TsaiChen-Peng ChenShu-An Lee
口試日期:2014-07-31
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:職業醫學與工業衛生研究所
學門:醫藥衛生學門
學類:公共衛生學類
論文出版年:2014
畢業學年度:102
語文別:中文
論文頁數:54
中文關鍵詞:密合度測試粒徑分布吸入效率洩漏方向
外文關鍵詞:Fit testParticle size distributionAspiration efficiencyLeak orientation
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根據OSHA規範,定性密合度測試(QLFT)方法適用於密合係數小於100之口罩。由於定性密合度測試受限於受測者對於感受性溶液的刺激,故測試結果通常無法有效驗證其實際防護效果。然而其測試方便性及成本低廉等因素使得QLFT仍時常被應用,其中又以糖精及苦味試劑最為普遍。即使QLFT所使用的霧化器已經被研發並販售於市面上許久,其輸出之粒徑分布卻鮮少有人去確認及定義。此外由於過去針對口罩不密合處的微粒穿透特性資料仍十分有限,因此本研究的目的即利用毛細管模擬口罩不密合處實驗探討其微粒穿透率特性,並以數值模擬方式計算最理想的定性密合度測試微粒粒徑分布。

  本研究中以長1、2cm直徑0.7、0.4 mm毛細管模擬口罩不密合處,並使用超音波霧化器產生多粒徑分布氯化鈉微粒作為挑戰氣膠,以氣動微粒分徑器(Aerodynamic Particle Sizer, APS)量測上、下游微粒濃度及粒徑分布以計算毛細管穿透率,實驗參數包含不同的流量大小以及毛細管方向。理論模式以微粒進入毛細管的吸入效率及重力沉降機制計算洩漏損失,並以實驗結果進行比較驗證。濾材穿透率則依據單一纖維理論進行計算。因此密合係數可結合濾材穿透率及不密合處收集效率進行計算並以不同質量中位粒徑及幾何標準偏差呈現。

  實驗結果符合理論模式之計算,表示微粒於毛細管之穿透特性受到吸入效率所影響,其機制和微粒粒徑顯著相關。在穩定流場中吸入效率所造成的微粒損失,隨著毛細管流量上升而增加。當毛細管較細長且呈水平方向時穿透率額外受重力沉降機制所影響,並隨流量下降而越顯著。實驗及模式的結果顯示不同洩漏大小、長度、方向、流量及濾材特性均會影響進入口罩內的總微粒量即密合係數。微粒的測試粒徑分布上限主要受到不密合處收集機制,而下限則以濾材穿透特性所決定。最理想的定性密合度測試粒徑分布條件考量25% 誤差後為0.4< MMD< 2.0 μm, GSD< 2,當密合條件需更準確之10%誤差,其範圍則為 0.5< MMD< 1.3 μm, GSD&;#8776; 1.5。


Qualitative fit test (QLFT) methods can only be used when a fit factor of 100 or less is considered to be an acceptable pass level, in accordance with OSHA regulations. This is largely due to the limitation of human sensitivity to the chemical stimulants used in QLFT. In general, QLFT has the disadvantages of chance of employee deception or bluffing, and limited protection-factor verification. However, it is getting more popular because of low equipment cost, high portability, and simple pass/fail results. Among the QLFT methods, saccharin and Bitrex are probably the most commonly used test agents. Several QLFT aerosol generators have been developed and commercially available, but the generated aerosol size distributions have not been well defined and justified. The data on aerosol penetration through faceseal leaks were still quite limited. Therefore, this study aimed to characterize the aerosol penetration through small diameter tubing, and to derive the appropriate range of size distribution of challenge aerosol particles for QLFT.

Microtubes with different length (1, 2 cm) and diameter (0.7, 0.4 mm) were employed to simulate faceseal leaks. Ultrasonic nebulizer was used to generate polydisperse NaCl particles with various size distributions as challenging aerosol. Aerosol number concentrations and size distributions upstream and downstream of the microtubes were measured by an Aerodynamic Particle Sizer (APS). Aerosol penetration data were taken at different flow rate through microtubes and under tube orientation (horizontal and perpendicular). Empirical models taking into account the aerosol aspiration efficiency and gravitational deposition were used to calculate the faceseal leakage. The modelled data were then compared with experimental results. The filter penetration was predicted based on the single fiber efficiency theory. Accordingly, fit factors, obtained by combining the filter penetration and faceseal leakage, were shown as a function of mass medium diameter and geometric standard deviation.

Experimental results agreed well with the modelled data, showing that aerosol penetration was significantly affected by aspiration efficiency which is a strong function of particle size. Aspiration effect increased with increasing leak flow through microtubes, given in the calm air environment. Gravitational deposition loss in the microtubes was apparent, especially when the tube was placed horizontally and leak flow was low. Experimental data and modelled results all showed that leak size, leak length, leak orientation, breathing flow, filter properties all affected and contributed to the total inward leakage, and therefore, the fit factor. The upper limit of the size distribution of challenge aerosols was mainly determined by the aerosol deposition in the faceseal leaks, while the lower limit was driven by the filter penetration. The optimal challenge aerosol size distribution for QLFT was found to be 0.4< MMD< 2.0 μm and GSD< 2, with 25% error. When a more accurate (10% error) fit factor was desired, the aerosol size distribution should be 0.5< MMD < 1.3 μm and GSD around 1.5.


目錄
致謝 I
中文摘要 II
英文摘要 IV
表目錄 VIII
圖目錄 IX
第一章 研究緣起與目的 1
第二章 文獻探討 2
2-1 密合度確認 2
2-1-1 定性密合度測試(Qualitative fit test) 2
2-1-2 定量密合度測試 (Quantitative fit test) 3
2-2 評估定性密合度測試的效能 4
2-2-1 濾材和不密合處的流量分配 5
2-2-2濾材過濾機制 7
2-2-3 濾材穿透率的計算及模擬 7
2-2-4 口罩不密合處收集機制 8
2-2-5不密合處毛細管穿透率的計算與模擬 9
2-3 定性密合度測試用霧化產生器 11
2-3-1 霧化產生器之種類 11
2-3-2 霧化產生器之原理 11
第三章 研究方法 13
3-1 實驗系統測試 13
3-1-1毛細管模擬口罩不密合處測試系統 13
3-1-2 氣動微粒分徑器 (Aerodynamic Particle Sizer, APS) 14
3-1-3 超音波霧化器 (Ultrasonic nebulizer) 14
3-2 數值模擬探討 15
3-2-1 測試粒徑分布產生模式 15
3-2-2 口罩不密合處穿透率 16
3-2-3 定性密合度密合係數 16
第四章 結果與討論 17
4-1 毛細管模擬口罩不密合處穿透率測試 17
4-1-1 口罩與毛細管模擬口罩不密合處之流量和壓降關係 17
4-1-2 毛細管模擬口罩不密合處穿透率 17
4-2 數值模擬毛細管穿透率 18
4-2-1 不同方向、長度、管徑對毛細管穿透率之影響 18
4-2-2 不同管徑下的密合係數 19
4-3 N100口罩之定性密合度測試粒徑分布需求評估 20
4-4 N95口罩之定性密合度測試粒徑分布需求評估 21
4-5 定性密合度測試微粒粒徑分布需求 21
第五章 結論與建議 23
第六章 參考文獻 24



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