微粒防護衣材質測試方法比較

Comparison of test methods for determining aerosol penetration through particulate protective clothing materials

卓融駿(Jung-Chun Cho)

指導教授 ： 陳志傑

國立臺灣大學/公共衛生學院/職業醫學與工業衛生研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.01289

摘要

個人防護衣是用來保護工作人員避免有害物質經由皮膚暴露。截至目前為止雖然有許多方法來可用來測試防護衣的防護性能，然而皆著重於針對液體噴濺以及蒸氣危害的測試，對於空氣中粒狀污染物的防護性能卻尚無一套成熟並廣為使用的測試規範。在不同的工作環境中，正確選擇防護衣可以帶來最適當的防護效果，過當及不足的防護皆會造成危害，應力求避免。因此，本研究最主要的目的是發展三種測試方法來評估防護衣對微粒的防護性能，三種方法依序為：(1)主動抽氣過濾法：研究在超低過濾表面風速下，微粒防護衣的的過濾狀況；(2) 內循環採樣法：利用內循環系統來進行微粒採樣，評估防護衣微粒防護性能；(3)螢光微粒測試法：以螢光微粒評估防護衣微粒防護性能。

不論是用在醫療照護者或是工業上所使用的各式各樣防護衣皆必須經過微粒過濾效率及阻抗測試。由於聚氨酯海綿具有容易清洗、可重複使用、容易控制各項物理特性等優點，如此可減低濾材之間的變異，進而有更優質的實驗數據。實驗採用定量輸出霧化器與超音波霧化噴嘴分別產生次微米級與微米級多粒徑分佈測試微粒。由於需要較高濃度的單一粒徑測試微粒，以凝結核氣膠產生器產生。微粒產生後經過氣膠電性中和器(Am-241)以中和微粒帶電，使其達到波茲曼電量平衡的狀態。微粒量測儀器則是以氣動微粒分徑器量測粒徑大於0.7微米的微粒濃度分佈；以電移動度掃描分徑器量測小於0.7微米的微粒濃度分佈。另外，以白光氣膠分徑儀量測0.1~20微米的微粒濃度分佈，用來檢驗APS的實驗數據力保正確性。

主動抽氣過濾法中，過濾風速設定範圍涵蓋0.01~20 cm/s。極低過濾風速利用大面積的濾材握持器及低抽氣流量來達成。實驗亦改變濾材的擺放方向，探討氣流與濾材表面的夾角對過濾造成的效應。內循環採樣法中，循環的流率、採樣系統配置以及環境風速是最重要的實驗參數。螢光微粒測試法利用螢光檢知器來計算不同微粒粒徑的穿透率。

由主動式採樣法的結果得知，在極低表面風速下，對較大的微粒而言重力沉降機制成為主要的過濾機制。重力沉降機制與慣性衝擊機制的轉換點能成功的以改變採樣的方向及表面風速來找出；內循環採樣法中發現環境風速對微粒穿透具有顯著影響，抽補氣流率則因為有稀釋效應的存在而影響穿透率之計算。不論是主動式採樣法或內循環採樣法，皆發現濾材在車縫邊的微粒穿透率顯著較高，顯示車縫邊將是濾材提升防護效果的關鍵；三種測試方法所測得之穿透率值分別差一個數量級，以主動式採樣法最高，螢光微粒法最低。實驗中所有的資料對微粒防護衣測試方法的擬定佔有重要的貢獻。

關鍵字

微粒穿透率 ； 微粒防護衣 ； 車縫邊 ； 螢光 ； 內循環系統

並列摘要

Personal protective clothing is designed to protect workers against hazardous substances that might come into contact with the skin. Several widely accepted test methods are available to measure barrier properties of protective clothing against liquid and/or vapor assaults, but there is no officially accepted test method for particulate protective clothing. For any given situation, equipment and clothing should be selected that provide an adequate level of protection. Overprotection as well as under-protection can be hazardous to the wearers and should be avoided. Accordingly, the main objective of this study was to develop three test methods for evaluating the aerosol penetration through particulate protective clothing materials: (1) Active sampling method: monitoring aerosol penetration through PPC under extremely low filtration velocity, (2) Closed-return sampling train method: using a closed-return to measure the PPC performance without active sampling, (3) Fluorescent aerosol method: using fluorescent aerosols to measure aerosol penetration through protective ensembles, without active sampling. The active sampling method is useful to illustrate the aerosol penetration through protective clothing, when the wears are in motion and vacuum might be created inside the clothing. Both fluorescent aerosol method and closed return sampling train method simulated wearers in static condition. Closed return sampling train method provided fast measurement results when coupled with real time aerosol size spectrometer or aerosol counter. However, fluorescent aerosol method theoretically provides the most accurate aerosol deposition rate.
In the present study, a variety of protective garments, currently used in health care industry, were tested for aerosol penetration and air resistance. Polyurethane foam filter was used as the reference filter media for their cleanability and reusability. These unique features reduce variability and lead to good quality experimental data. In order to cover a broad size range, a constant output atomizer and an ultrasonic atomizing nozzle was used to generate polydisperse sub-micrometer-sized and micrometer-sized particles, respectively. Whenever high concentration monodisperse challenge aerosols are needed, a condensation nucleation aerosol generator was used. The aerosol output was neutralized by using a 25 mCi radioactive source, Am-241, and then introduced into the mixing (test) chamber. Two different particle size spectrometers were used to measure the aerosol concentrations and size distributions upstream and downstream of the filters: a scanning mobility particle sizer (SMPS) for particles smaller than 0.7 mm, and an aerodynamic particle sizer (APS) for particles larger than 0.7 mm. The third aerosol instrument, a Welas 3000 size spectrometer, covering size range from 0.1 to 20 mm, was used to double-check the aerosol penetration measurements by APS and SMPS.
For active sampling method, filtration velocity ranging from 0.01 to 20 cm/sec was adopted to study the flow dependency. This extremely low face velocity was made possible by using a large filter hold and the lowest sampling flow feasible. The effect of filter orientation on the filter penetration was also be investigated by rotating the filter holder to be either parallel or perpendicular to the flow. The closed-return sampling train method was conducted in a wind tunnel-like chamber. The flow rate of the closed-return system, the configuration of the sampling train, and the external approaching velocity were the principal operating parameters. The fluorescent aerosol method shared the same test apparatus with the closed-return sampling train method, except that monodisperse uranine particles, instead of polydisperse potassium sodium tartrate, were used as challenge aerosols. A fluorescence meter was used to measure the aerosol penetration through protective materials.
Under extremely low face velocity, gravitational settling became the principal filtration mechanism. This was particularly true for large particles. Transition from gravitational settling to inertial impaction was best demonstrated by rotating sampling orientation and changing face velocity. Both active sampling method and closed return sampling train method showed that the aerosol penetration through clothing with seam was much higher than that of clothing without seam. The approaching velocity played an important role pushing aerosols through particulate protective clothing. However, this effect diminished as the velocity decreased or the air resistance of the clothing material increased. In general, the aerosol penetration measured by active sampling method (filtration velocity in the proximity of 0.01 cm/sec) was about 10 times higher than that of closed return sampling train method. The aerosol penetration determined by fluorescent aerosol method decreased by a factor of 100 when compared to active sampling method.

並列關鍵字

aerosol penetration ； protective clothing ； seam ； uranine aerosol ； closed-return sampling

參考文獻

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