Step 1. Write the penetration (Pt) equation:
From the figures in USEPA-84/03, p. 9-12, we read (dp)cut/dgm, for Pt∗ = 0.01, and σgm = 3.0;[dp]cut/dgm equals 0.063. Because dgm = 12 μm, the scrubber must be able to collect particles of size 0.063 × 12 = 0.76 μm (with at least 50% efficiency) to achieve an overall scrubber efficiency of 99%.