空氣年齡概念在作業場所通風特性評估之應用

Application of the 'Age of Air' Concept in Envaluating Ventilation Characteristics in a Work Place

本研究主要目的在於以「空氣年齡」概念與追蹤氣體技術瞭解待測空間中不同位置的通風效能差異、推測可能之氣流型態，期能適用於使用整體換氣之作業場所其通風特性之測定與評估。通風為工業衛生中危害控制系統之一環，通風功能之良窳對現場工作人員之健康有相當重要的影響。此外，瞭解作業環境之通風特性有助於提出改善之建議與風險評估。本研究選擇在半導體業之黃光室中進行。在待測空間之空調入口內，以脈衝注射法釋放追蹤氣體二氧化碳（CO2），由擺設在作業場所中不同位置的紅外光吸收光譜儀－MIRAN，記錄該測量地點之追蹤氣體濃度變化與時間之關係。由此估算出各測量地點之平均空氣年齡與空氣交換效率等通風參數，以瞭解整個作業場所空間的通風狀況。由現場測量之結果顯示：作業環境之空調出、回風口位置與形式為影響測量地點通風特性之關鍵。在原設計氣流型態為置換式氣流的黃光室中，其中一回風口處測得之平均空氣年齡小於空間其他位置平均空氣年齡的1/4，可知此作業環境有氣流短路的現象產生。此外，整個空間之溫度在呼吸區高度處由右至左遞增而呈階梯式分布，也顯示了由於空調出、回風口的設計與使用不良，以致於通風效用在空間不同位置呈顯著差異。

The primary objective of this study is to apply the 'age of air' concept and tracer gas techniques for evaluating ventilation parameters and investigating ventilation characteristics in work places equipped with a general ventilation system. Designed and operated properly, a ventilation system can be effective for hazards control. A good understanding of ventilation characteristics should be helpful in improving the ventilation performance and providing information for risk assessment. A clean room was selected for this study. After a tracer gas (carbon dioxide) was released into the air supply, its concentrations were measured at various locations by non-dispersive infrared spectrophotometers(MIRAN). The ventilation parameters, such as average age of air and air exchange efficiency, were then calculated from the results obtained by the tracer gas pulse injection method. The results of field measurements indicate that the position and type of air inlets and outlets were the key factors influencing the ventilation characteristics. In the clean room studied, the air was found to be short-circuiting and the average age of air at one of the air outlets was lower than one-fourth of the highest value measured in the clean room. Moreover, the room temperature was increasing from the right side to the left side in the clean room because the heat removal ability varies from location to location. This non-uniform temperature distribution indicates that inappropriate design and operation of the air inlets and outlets have a significant influence on ventilation effectiveness.