家用瓦斯熱水器一氧化碳模擬分析與中毒防制之研究

Abstract

台灣人口密度隨著環境變遷不斷地持續增加，民眾為追求更多之生活空間，部分家庭將熱水器安裝於前、後陽台或室內，且因宵小橫行並將陽台裝設防盜窗，導致形成一密閉空間，每當天氣較為寒冷時，常因熱水器燃燒不完全產生一氧化碳，發生室內人員中毒死亡的悲劇，另由全台幾個案例亦發現，民眾雖有開窗保持通風之防制行為，但也同樣造成屋內人員中毒死亡之慘劇。本研究使用NIST（National Institute of Standard and Technology , U.S.A，美國國家標準局火災實驗室）所發展之FDS（Fire Dynamics Simulator）軟體，模擬瓦斯熱水器使用時之陽台環境如密閉陽台、開啟對內室內門、強制通風等3個情境，經過FDS軟體計算後得到陽台及相鄰空間內之氧氣、一氧化碳及二氧化碳等氣體濃度數據，發現模擬數據曲線與勞研所全尺寸實驗所得之數據有高度吻合趨勢，觀察氧氣、一氧化碳及二氧化碳等3種氣體在室內空間的濃度變化，相互之間亦符合燃燒邏輯，例如當室內氧氣濃度低於15％以下時，一氧化碳濃度會明顯迅速上升，甚至達到1500ppm以上，在短時間即可使人致死，另外當強制通風量足夠供給熱水器完全燃燒時，室內一氧化碳濃度則會保持在很低的濃度，對人體無害。 成功建立FDS模擬瓦斯熱水器使用狀態之電腦模型後，在陽台未晾曬衣物之淨空間內，嘗試以不同之開窗面積、外氣風速及熱水器型號等變數探討安全使用瓦斯熱水器之模式，得出之安全建議為在陽台空間大（等）於14m3，使用瓦斯熱水器規格小（等）於16L（33.1KW），關閉陽台與室內相通門窗之環境下，將陽台對外窗開啟0.2m2以上時，即可保持室內空間之人員安全。 以上成果證實本研究所建構之電腦模型及參數設定可用於模擬家用瓦斯熱水器使用情境，優點除了免除全尺寸實驗產生之人員中毒風險與重複實驗之高成本外，並彌補實驗中觀測數據之不足，日後研究人員更可進一步利用此模型進行更多防制中毒之研究。

This study adopted FDS (Fire Dynamics Simulator), developed by NIST (National Institute of Standard and Technology, to simulate 3 scenarios, different balcony environments when using gas water heater, such as airtight balcony, indoor door with openings, force ventilation. According to FDS simulation results, this study obtained several gas concentration data such as oxygen, carbon monoxide and carbon dioxide in balcony and adjacent compartment. Also, we could find that data of the FDS simulation, O2, CO, and CO2 concentration, correspond highly with full-scale experimental results made by Institute of Occupational Safety & Health. Through observing O2, CO, and CO2 concentration curve in the indoor compartment, we also find that when the indoor O2 concentration was lower than 15%, the CO concentration would rise rapidly and even reached above 1500ppm, causing death in short time so the phenomena correspond logically with combustion theory. In addition, when the force ventilation model supplied the water heater with enough air to burn, the indoor CO concentration will keep low and unharmful concentration to human body. After setting up the computer models of FDS simulation related to gas water heater performance, the balcony is not drying clothes , the study also adopted diverse variables such as, the opening area of window, outdoor wind speed, and water heater types, to analyze deeply user’s safety regarding gas water heater. In a result, the study found out that while balcony area is above 14m3, water heater type is below 16L（33.1KW）, and the indoor window ,connecting balcony with room, is closed, if the opening on the outdoor window of the balcony is above 0.2m2, this can ensure the personal security of the indoor space. In accordance with the above-mentioned results, it is clear that FDS models and several parameters set up by this study could simulate a series of household gas water heater scenarios effectively and logically. Therefore, not only could this study avoid poison risk by conducting full-scale experiments, but obtained CO poison prevention models and strategies to study further in the future.