| Abstract: | 目前氫氯酸的評估方法，尚未針對瞬間暴露濃度能立即呈現的方法，導致勞工即使暴露在時量容許濃度內，仍可能因為瞬間的高濃度，而暴露在酸危害。本研究考量氫氯酸之容許濃度為最高容許濃度，因此選擇某鋼鐵工廠之酸洗作業環境中，利用商業化之直讀式儀器進行時間與濃度之監測，同時以定量採樣分析方法進行測定氫氯酸之暴露量，結合兩種評估方法，以瞭解氫氯酸濃度隨時間變化情形，以進行判斷該酸洗作業氫氯酸之瞬間最高暴露濃度。
本研究以某鋼鐵廠酸洗槽為研究地點，分別於酸洗內區、酸洗中區(人員作業區域)、與酸洗外區，進行區域採樣，採樣期間以NIOSH 7907採樣方法(石英濾紙和pump)和直讀式儀器(MX6 iBrid氣體探測器)同步進行監測，並利用八階分徑採樣器進行評估粒徑分布情形，同時選擇一名酸洗作業勞工進行個人採樣，所採集之樣本由實驗室進行氫氯酸分析。
依短時間(30分鐘)同步監測與分析結果顯示，直讀式儀器即時監測與定量採樣之測定，兩者評估方法於酸洗作業場所之濃度分佈具有高度相關性，r為0.91。以長時間(4小時)監測氫氯酸濃度值，於酸洗內區有較高之氣相濃度(97%)，酸洗中區(人員作業區域)及個人採樣所採得之氣相占比分別為88%及87%，酸洗外區所採得之氣相占比為84%，可發現空氣中氫氯酸濃度越高時，其氣相佔比也相對較高。在粒徑分布之評估，可發現僅酸洗內區呈現雙峰分布，而酸洗中區與酸洗外區有一致的結果，皆呈現單峰分布，推測應與酸洗內區有較高氣相占比有關。另一方面，以直讀式儀器連續監測之結果，酸洗內區95th值為10.2ppm、酸洗中區95th值為3.6ppm、酸洗外區95th值為2.2ppm、個人採樣95th值為2.6ppm。結合定量分析與直讀儀隨時間變化之監測進行推估氫氯酸濃度隨時間變化之結果，發現無論是在酸洗外區、酸洗中區(人員作業區域)、酸洗內區、與個人濃度暴露之推估結果，皆有超過於PEL-C(5ppm)之時間點，應加強人員之防護或進行有效之工程控制。
藉由上述結果，本研究可藉由直讀式儀器之輔助，推估短時間作業勞工之任何時間的實際暴露濃度，以瞭解是否超過最高容許濃度之規範。建議事業單位在進行具有最高容許濃度規範物質時，可搭配直讀式儀器之輔助監測，將可協助瞭解最高濃度暴露之情形。
At present, the acid evaluation method does not have an immediate display results for the instantaneous exposure concentration, which causes the worker to be exposed to the acid hazard due to the instantaneous high concentration even if it is exposed to the allowable concentration. Considering the allowable concentration of hydrochloric acid is the maximum allowable concentration, the objective was that a commercial direct reading instrument was selected to monitor the concentration of hydrochloric acid with time variation and the traditional sampling was selected to evaluate the exposure amount of hydrochloric acid in the selected period during the pickling process in a steel factory. In order to determine the instantaneous maximum exposure concentration of hydrochloric acid, the two evaluation methods was used to estimate the instantaneous maximum exposure concentration of hydrochloric acid over time.
In this study, used steel pickling tank as the research site, sampled in the pickling inner zone, the pickling middle zone (working area), and the pickling outer zone respectively. Used NIOSH 7907 sampling method (quartz filters with pump) and gas detector (MX6 iBrid) to monitored in the same time, size-selective sampler to evaluate the particle size distribution, selected a pickling worker for the personal sampling, the collected sample would analysis for hydrochloric acid by the laboratory.
According to the short-time (30 minutes) synchronous monitoring and results of analysis indicated that the real-time monitoring of gas detector and quantitative sampling determination were highly correlated with the concentration distribution of the pickling workplace, r is 0.91. Monitored the concentration of hydrochloric acid for a long time (4 hours), have a higher gas phase concentration in the pickling inner zone (97%), the pickling middle zone (working area) was 88%, the personal sampling was 87%, the pickling outer zone was 84%. We found that the higher the concentration of hydrochloric acid in the air, the higher the gas phase ratio. In the evaluation of the particle size distribution, we found that only the inner pickling zone appeared a bimodal distribution, however the middle pickling zone and the outer pickling zone had same results, appeared a single peak distribution, so we supposed that because of the higher gas phase in the outer pickling zone. On the other hand, with the result of continuous monitoring by gas detector, the 95th value of the inner pickling zone was 10.2ppm, the 95th value of the middle pickling zone was 3.6ppm, the 95th value of the outer pickling zone was 2.2ppm, and the 95th value of the personal sampling was 2.6. ppm. Combined with the quantitative analysis and the monitoring result of the gas detector over time, we found the results in the outer, middle, inner pickling area and result of personal sampling were higher than PEL-Ceiling (5ppm), we should to reinforce the personal protection or engineering control.
Based on the above results, this study can estimate the actual exposure concentration of the short-time workers in any time by used gas detector to found whether the PEL-Ceiling was exceeded or not. We suggested that using gas detector for monitoring while using the substance of PEL-Ceiling was helpful for understand the situation of the highest concentration exposure. |
