整體換氣壓力差對有害物散布之影響

A Study on Contaminant Dispersion and Pressure Difference of General Ventilation

在整體的通風系統中，利用兩個鄰近的區域產生壓力差去控制危害物的逸散是一種重要的技術，例如在醫療院所的手術室或感染隔離室、半導體業隔離機台，都是採用壓力差來避免污染互相影響。然而在相互鄰近的區域設有開口的情況下，在打開開口時，將使得氣流變得更為複雜，是否會影響隔離控制效果，將是設計規劃的重要因素。研究利用二氧化碳追蹤氣體技術，探討在兩鄰近區域產生特定壓力差下，打開開口後，高壓區受到低壓區危害物影響情形，藉以評定危害物控制效果，研究開口面積模擬某手術室大門的比例，壓力模擬 0.01 in-H2O 至 0.06 in-H2O，結果發現當開口面積過大或壓力差太小，低壓區危害物將會產生逸散，並隨著開口面積加大，壓力差減小，逸散效應愈明顯，可知利用壓力差來控制危害物逸散，必須考慮壓力差及開口面積的大小。而比較 CDC 對於肺結核隔離病房的負壓要求來看，在研究實驗條件下，可能無法有效控制危害物逸散，而在 CDC 所有相對的控制措施及不同開口部形狀下，是否產生逸散則必須進一步探討。

Pressure difference between different zones is an important factor in controling the dispersion of air-borne contamination in a general ventilation system. Maintaining certain level of pressure difference is essential to achieve effective control in areas such as operating and isolation rooms. However, the pressure difference will affect the control of air-borne contaminats when opening the door between different zones. This study used CO2 tracer gas technology to evaluate the contaminant dispersion under various pressure differences. The door size was simulated with real operating rooms with the pressure drop varying from 0.01 in-H2O to 0.06 in-H2O. The air-borne contaminant in low-pressure zone would disperse to high-pressure zone if the door is too large or the pressure difference is too low. Lower pressure difference or larger door sizes will cause more air-borne contaminant dispersion. Using pressure difference to control the dispersion of air-borne contaminats in general ventilation must consider the pressure drop and door size. Comparison with the CDC requirement for TB isolation rooms, the contaminant dispersion may not be controlled under tested conditions. A study on CDC contaminant dispersion requirement for TB isolation rooms with different shapes of doors is highly recommended.