Smoke varies from 0.6 BSU at low load to 5.6 BSU at full load for WPO whereas for WPO 70 it varies from
0.61 BSU at low load to 5.5 BSU at full load. For WPO 50, it varies from 0.51 BSU at low load to 5.23 BSU at full load, from 0.45 BSU at low load to 5.21 BSU at full load WPO 30.