802 through the control unit 2 inlet line 420 through the inlet 2 flexible hose 430 entering the bottom and exiting the top of control unit no 2 802 passing through the outlet 2 flexible hose 440 to the outlet 2 hard pipe to discharge valve no 1 500 given that control unit 2 outlet valve 470 and discharge valve 2 510 are closed flow from the pollution control device 150 exits via the control device outlet 520 while the above description illustrates one configuration of how the function of two control units may be coordinated other combinations may allow for the same function and in many instances specific pieces of pipe could be eliminated simplifying the system for example outlet 1 flexible hose could be coupled directly to control unit 1 outlet 360 without first passing through outlet 1 hard pipe 350 in all cases hard pipes may be substituted with flexible pipe hoses and vice versa configuration with a single control unit would be significantly simplified and configurations with more than two control units would become more involved reference is now made to fig3 which shows a control unit in greater detail control units may be identically configured or may be differently configured in this example control unit no 1 801 and control unit no 2 802 are similarly configured vapor enters the control unit via an internal control unit diffuser line 820 the control unit contains an absorbent liquid designated as control unit liquid 860 a purpose of the liquid is to capture entrained or condensed liquids prior to proceeding to the control unit carbon 870 which is supported by the control unit screen support 830 and the lower control unit screen 840 and optionally retained by an.