High operating pressure increases gas density and changes mist eliminator pressure drop, droplet behavior, and re-entrainment limits. A velocity acceptable at atmospheric conditions should not be applied directly to pressurized service without recalculating the hydraulic basis.

Mist eliminator datasheets should be compared by process basis, gas-flow condition, performance definition, wet or dry pressure drop, active thickness, mesh or vane geometry, material, supports, and segmentation. Similar-looking specifications may represent different technical scopes.

Intermittent liquid slugs can saturate a mist eliminator far faster than ordinary continuous mist loading, causing sudden pressure-drop spikes, flooding, re-entrainment, and possible mechanical movement. Average liquid loading alone does not describe slugging duty.

Upflow, downflow, and horizontal mist eliminators experience different relationships between gas force and gravity. Flow direction affects drainage, re-entrainment, support requirements, and vane orientation, so separator geometry must match the actual installation.

When droplet size is unknown, mist eliminator selection can begin from the droplet-generation mechanism, liquid loading, fouling condition, gas flow, downstream sensitivity, and existing operating history. Unknown data should remain identified as uncertainty rather than replaced by an arbitrary assumed micron value.