Study on method for estimating TWA with grab sample determinatiom

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.