沖水馬桶氣膠逸散控制裝置的開發與測試

Abstract

沖馬桶，一個每天的例行公事，卻可能成為使用者感染SARS或COVID-19的原因。研究發現馬桶沖水過程會產生10^5顆的細小微粒，這些微粒可能攜帶感染性微生物或是病人的藥物殘留，對使用者造成健康威脅。為解決此問題，先前研究提出不同的解法因應，包含對整體浴廁通風進行改善，可稀釋廁所中微粒濃度，卻無法保證完全清除；或是評估蓋子的使用，雖能相當程度阻擋微粒沖出，卻仍然能從縫隙洩漏；以及針對盆內控制，如加裝紫外線消毒使微生物失去活性，然其只能針對於生物性微粒，且作用時間可能不夠長。 為彌補先前文獻不足，本研究針對微粒產生源頭進行工程控制，透過抽氣加上蓋子構型的改善，目的為使整體微粒控制裝置達到100%的微粒捕集，並考量能源使用，比較各參數條件之置換空氣體積(將達99.9%微粒捕集的所需流量與盆內濃度降低99.9%之清除時間相乘所得)相對原設計的比例，以得到改善率最多的參數與設計。研究將市售馬桶置於可控乾淨條件之測試艙中，使量測過程不受環境微粒干擾。使用兩臺凝結式微粒計數器，同時對環境濃度(馬桶外)與盆中(馬桶內)進行濃度監測，以了解微粒被裝置捕集的成效與馬桶內部達到清除的所需時間。 結果發現，當單純使用馬桶蓋，對於微粒有60%的捕集效果，然沖水後盆內微粒會長時間懸浮在盆內，因此透過加上風扇抽氣，可於358 L/min達99.9%的微粒捕集，約32秒達到盆內濃度下降99.9%的乾淨程度，此時流量與時間相乘所得之置換空氣體積約為191 L，訂為置換空氣體積比100%。接著比較不同縫隙橫向面積、高度，以及內部導入的垂直延伸板與盆內體積，其各別條件在達到99.9%捕集效率的最低置換空氣體積比為50.0%、49.9%、37.9%與31.0%，以填充實體使盆內降至3L的條件為最佳。進一步組合不同參數之最佳條件，可發現以3 L盆內體積組合0 mm的縫隙高度有最低之置換空氣體積比(25.1%)。然在此條件下所需清除時間為60秒，約為其他條件的2至3倍，因此提升流量以降低時間使各條件在同為24秒清除時間下比較，此時該條件所需置換空氣體積比上升至42.3%，最低置換空氣體積比則為3 L盆內體積與19 cm²的縫隙面積之組合(30.6%)。 本研究在達到99.9%捕集效率的前提下，以置換空氣體積比與清除時間作為指標，提出兩種最佳設計原型，分別適用於家用與公共場所。所需要的共同設計包含平面的蓋子、風扇與濾材組合、後側盡量密封與內部加裝實體。家用馬桶因使用間隔較長，對於清除時間要求較寬鬆，因此可使縫隙盡可能密封，此時清除時間較長但可使用較低之抽氣流量，因此置換空氣體積比最低。公共場所的馬桶則因使用頻繁，需盡可能降低清除時間，此時不可將縫隙密封，而是留下進氣口使內部氣流更流通，雖須以更高流量使微粒不往外逸散，但能夠將清除時間降低。

Toilet flushing, a routine daily activity, may expose users to infectious diseases such as SARS and COVID-19. Previous studies have shown that flushing generates approximately 10⁵ fine particles that may carry infectious microorganisms or pharmaceutical residues, posing potential health risks. Several control strategies have been proposed, including improving bathroom ventilation to dilute airborne particles, although complete removal cannot be guaranteed; using toilet lids to reduce particle escape, although particles may still leak through lid gaps; and applying ultraviolet (UV) disinfection inside the bowl to inactivate microorganisms, although it is only effective against biological aerosols and may not provide sufficient exposure time. To address these limitations, this study developed an engineering control strategy targeting the particle source by combining suction with optimized toilet lid configurations. The objective was to achieve complete particle capture while considering energy-related performance. Different design parameters were evaluated using the air replacement volume ratio, defined as the suction flow rate required to achieve 99.9% particle capture multiplied by the in-bowl clearance time required for the particle concentration to decrease by 99.9%. A commercial toilet was installed in a clean environmental chamber to eliminate background particle interference. Two condensation particle counters simultaneously monitored particle concentrations outside and inside the toilet bowl to evaluate capture efficiency and in-bowl clearance time. Results showed that using a toilet lid alone achieved approximately 60% particle capture, while particles remained suspended inside the bowl for an extended period after flushing. By adding suction, 99.9% particle capture was achieved at 358 L/min, and the in-bowl particle concentration was reduced by 99.9% within approximately 32 s. Under this condition, the air replacement volume was 191 L and was defined as an air replacement volume ratio of 100%. The effects of gap lateral area, gap height, a vertical extension plate, and residue toilet volume were subsequently investigated. The minimum air replacement volume ratios required to achieve 99.9% capture efficiency were 50.0%, 49.9%, 37.9%, and 31.0%, respectively, with the 3 L residue toilet volume providing the best individual performance. Combining the optimal parameters further reduced the air replacement volume ratio to 25.1% using a 3 L residue toilet volume with a 0 mm gap height. However, this configuration required 60 s for in bowl clearance, approximately two to three times longer than the other conditions. When all configurations were compared under the same 24 s clearance time by increasing the suction flow rate, the air replacement volume ratio of this configuration increased to 42.3%, whereas the lowest value (30.6%) was obtained using the combination of a 3 L residue toilet volume and a 19 cm² gap area. Based on the criteria of 99.9% particle capture, air replacement volume ratio, and clearance time, two optimal design prototypes were proposed for residential and public toilets. Both designs include a flat toilet lid, a fan-HEPA filter assembly, a sealed rear gap, and a solid body installed inside the toilet bowl. For residential toilets, where the interval between uses is relatively long, the gap can be sealed as much as possible to minimize the air replacement volume ratio, despite requiring a longer clearance time. In contrast, public toilets require rapid clearance because of frequent use. Therefore, an inlet gap should be maintained to enhance airflow circulation inside the bowl. Although a higher suction flow rate is required to prevent particle leakage, the clearance time can be substantially reduced.