For the PM collected above S6 (PM 1.1–2.1 ), the bestefficiencies were obtained for a speed of 121.3 m/s, fol-lowed by 76.6 m/s. For PM smaller than 1.0 μm, that is,from stage 6, at a speed of 49.3 m/s, the best efficiencyresults were obtained, followed by a speed of 121.1 m/s.Figure 3 shows the removal efficiencies for each diam-eter range in the Andersen cascade impactor, withV th = 174 m/s and a water flow rate of 6.0 L/min for twotests: Test 1—PM emission concentrations for the Ven-turi off (Tgas = 274.8 °C) and on (Tgas = 244.0 °C) andTest 2—PM emission concentrations for the Venturi off(Tgas = 172.3 °C) and on (Tgas = 244.0 °C). The highest effi-ciencies occurred for the 3.3–4.7 μm (S4) and 2.1–3.3 μm(S5) ranges, with values of 94.3% and 90.6% for Test 1,and 88.2% and 87.4% for Test 2, respectively. The lowestefficiencies are represented in the smallest PM diameterranges of 0.7–1.1 μm (S7) and 0–0.4 μm (backup stage) 1 3with maximum values of 27.1% for the two ranges, respec-tively. This reveals the efficiency of the Venturi scrubberin collecting particles above 2.5 μm to the detriment ofsmaller particles, which are more difficult to collect.