定点采样法估测TWA值探讨

Study on method for estimating TWA with grab sample determinatiom

[目的 ] 探索一种从最高容许浓度 (MAC)过渡到 8小时时间加权平均浓度 (TWA)检测的定点采样 (GrabSample)方法。 [方法 ] 利用电子计算机技术对含一氧化碳的环境进行不同方式的模拟采样 ,分析采样结果与总体的符合情况 ,以确定合适的采样方法。 [结果 ] 用采样频率将工作时间等分 ,在每一等分时间段内随机确定采样时机 ,或在第一等分时间段内随机 ,以后加上相等时间间隔确定采样时机 ,当采样频率适当时 ,可以得到与全程采样相近的TWA值 ;采样频率 (It)可根据采样时间 (Ts)用方程式It=36 .61 8Ts- 0 .50 4 5计算。 [结论 ] 沿用MAC的标准采样方法 ,增加采样频率并用推荐方法确定采样时机 。

To search a method using grab sampling of 8h time weighted average concentration(TWA) to replace the Maximum alowable concentration(MAC). Computer technology was used to simulate sampling carbon monoxide with different methods from various workplaces. Those sampling methods were selected for practical use when the results of their samples were very similar to those of the population. The whole working time was divided into several sampling sections. Select a random beginning time for sampling in each section or just in the first section,then plus a fixed time length to decide the beginning time for sampling in the next section. If the frequency of sampling was proper,the TWA values from grab samplings were very similar to those from full period single 8h-samplings. The relationship of sampling frequency(I t)and sampling time(T s)could be shown as I t=36.618T s -0.5045 . [Conclusion] According to the recommended MAC standard sampling time with additional sampling at a certain frequency,most of the MAC standard sampling processes can be used by grab sampling to estimate the TWA values of the samples which are very similar to those of the population.