| Type | Operating mechanism | Assembly | Function | Remarks |
| Settling tank knockout drum | Gravity | Tank (upright or horizontal) | Slowing down the gas flow so much that the settling velocity is higher than the gas velocity. | Simple, inexpensive apparatus for very gross drops, poor efficiency, rare use. |
| Fiber filter filtering candle | Mechanical filter | Case with compact packing of fibers on different single or individual filtering candles | Single drops are brought in touch with the fibers, flow together, increase and fall down due to gravity. The filtering candle prevents the passing of droplets while gas flows through. | Voluminous apparatus with very low face velocity and low liquid loading preferably for very small drops; the danger of clogging and build-up. |
| Electrostatic precipitator | Electrostatic forces | Case with electrodes | The drops are electro-charged and attracted to the collecting electrodes. | Complicated, expensive apparatus for extremely fine drops, very high efficiency, rare use. |
| Cyclone | Mass moment of inertia | Tank with the installation which forces the gas flow to rotate | Based on rotation separation because of varying density, the drops are eliminated along the tank walls. | Simple and voluminous apparatus for middle-sized drops, good efficiency, frequent use. |
| Wire mesh | Mass moment of inertia | Tank with a pack of several layers of wire mesh of undulating wires; compact wire mesh with high porosity | The drops are brought in touch with the wire surface, flow together, coalesce and fall down due to gravity. | Voluminous apparatus with low face velocities for low liquid loading and very fine drops, the danger of clogging and build-up. |
| Impingement eliminator | Mass moment of inertia | Tank with a set of profile plates of different types | Gas flow is split up into many single flows and repeatedly deflected. Due to inertia, the drops cannot follow the flow of the gas and thus are eliminated on the impingement surfaces. | Small compact construction because of high face velocity, very high efficiency even for very fine drops, low-pressure drop on well-formed profiles, and increasing use. |
