Feasibility test of cellulose filter for collection of sulfuric acid mists

Exploring affordable and reliable filters to sample sulfuric acid mists is of interest because the polytetrafluoroethylene filters recommended by NIOSH Method 7908 are relatively costly. In this study, the feasibility of hardened cellulose filters such as Whatman grade 540, 541, and 542 filters were investigated for sampling sulfuric acid mists. Thirty-minute collection efficiency tests showed low collection efficiency for Whatman grade 540 and 541 filters while Whatman grade 542 filters exhibited high collection efficiency because of its smaller pore size. Eight-hour collection efficiency tests for the concentration of ca. 5000 µg/m3 showed Whatman grade 542 filters retained 95% collection efficiency. The collection efficiency over eight hours neither increased nor decreased because the mists might have been absorbed or have formed a thin layer on the fiber and the filter structural integrity did not change. The higher collection efficiency was at the expense of a higher pressure drop; however, the pressure drop was still under the back pressure limit for most personal pumps. The integrity test showed that under the typical concentration in the occupational environment the hardened cellulose filters can maintain integrity for more than seven days. In summary, Whatman grade 542 filter is a suitable alternative for measuring sulfuric acid mists.