The specific behavior of antifoam use was studied in a particular plant. The goal was to find a solution for applying the new antifoam for the best compatibility with amine systems. A gas sweetening unit was installed to remove hydrogen sulfide (H₂S) contained in a high-pressure (HP) natural gas stream. The solvent used for the H₂S removal from the gaseous stream was a 34 wt% diethanolamine (DEA) solution, and the designed plant treating capacity was 250 million standard cubic feet per day (MMscfd) of HP sour gas. Due to bad filtration and an improper antifoam selection, an upset occurred that created foaming at the contactor tower. Six months after the unit startup, the deferential pressure of the lean/rich (L/R) exchanger was increased to 4 bar (allowed limitation was 0.7 bar). An unplanned shutdown of the sweetening plant occurred since cleaning was needed for the L/R amine heat exchangers. It took maintenance 12 hours to do the turnaround.