When an HCl pickling scrubber loses removal efficiency while pressure drop remains normal, inspect for oil-mist contamination and hydrophobic films. Oil can reduce aqueous wetting, spread through the recirculation loop, and lower effective packing area without causing severe blockage.

Marine exhaust scrubber design must consider soot, ash, oily particulate, seawater salts, evaporation, ship motion, wash-water solids, and allowable engine backpressure. Fine random packing can provide strong contact but may become an unintended soot-and-salt filter unless the solids duty is carefully controlled.

For seawater packed scrubbers, long-term reliability should include biofouling as well as alkalinity and chloride corrosion. Low-flow zones, stagnant operation, distributor branches, packing surface area, trapped solids, cleaning access, and water-treatment strategy can determine whether the tower maintains its original hydraulic capacity.

When a formaldehyde absorber develops white deposits in cold or stagnant sections, review formaldehyde concentration, water evaporation, stabilizer conditions, minimum liquid temperature, shutdown residence time, distributor geometry, and deposit identity. The fouling mechanism can be fundamentally different from mineral scaling.

When a geothermal H₂S scrubber develops silica-rich scale, evaluate upstream brine carryover, cooling profile, water chemistry, pH, packing openness, distributor blockage, and solids removal. A corrosion-resistant packing can still lose capacity rapidly if mineral-bearing droplets continuously enter the tower.