On the filtering characteristic features of the two kinds of common masks used in an underground uranium mines

The paper is oriented at making an exploration of the efficiency of the two kinds of frequently-used face masks in underground uranium mines for filtering the aerosol particles. For our research purpose,we have done a series of related experiments by using APS spectrometer model 3321 to trace the filtering features of gauze mask and KN95 mask in a uranium mine in China south.The results of our experiments indicate that in the actual uranium mining environment:( 1) The filtering efficiency of the gauze mask to PM10 ranges from 61. 62% to 99. 02%,with the average filtering efficiency being 76%,whereas the filtering efficiency of the gauze mask to PM2. 5stands between 43. 70% and 80. 17%,with the average filtering efficiency being 61%. On the other hand,as to KN95 mask,the filtering efficiency to PM10 can be as high as 91. 52%-99. 92% and average value is 95%,while the filtering efficiency to PM2. 5is 89. 74%-98. 54% and average value is 93%,respectively.( 2) And,in terms of 0. 5-3. 5 μm,the filtering efficiency of the two masks to different sizes of particles can both be expected to rise with the increase of particle size.What is more,in a range of 3. 5-10 μm,the filtration efficiency of the two masks can be close to 100%.( 3) It can also be found that most of the minute aerosols filtrated out by the masks either in terms of mass concentration or number concentration,spread within the range of less than 2. 5 μm. What is more to be added,firstly,the filtration efficiency of gauze mask to PM10 and PM2. 5may not be steady under the mines; in contrast,the filtration efficiency of KN95 mask proves to be combatively stable and is less affected by the environmental factors. Secondly,the filtration efficiency of the gauze mask is likely significantly lower than KN95 mask both for PM10 and PM2. 5,even to the degree that the gauze mask may not be suitable for the anti-dust mask purpose for its filtration efficiencies both in the case of PM10 and in that of PM2. 5are much below the national standard values. Therefore,whereas the average filtration efficiency of KN95 mask to PM10 comes up to the national standard,its average efficiency in filtering PM2. 5is2% lower than the national standard value( 95%). Thirdly,the main pollutant aerosol to be filtered by the two masks is PM2. 5.Therefore,when estimating uranium mine operators' respiratory irradiation dose which are caused by inhaling the radioactive aerosol particles,it is important to lay stress on the effects of concentration,size distribution and chemical composition of the minute particles,especially those of PM2. 5,on the irradiation dose estimation.