Outdoor packed scrubbers in freezing climates should be reviewed for local wall cooling, trapped water, frozen distributor branches, demister icing, drain blockage, shutdown conditions, insulation, and heat tracing. A tower can experience severe pressure-drop and carryover problems even when the bulk sump liquid remains above freezing.

When activated carbon follows a packed wet scrubber, evaluate outlet humidity, gas temperature, downstream condensation, demister carryover, dissolved salts, duct drainage, real gas velocity, and the carbon supplier's allowable inlet condition. A demister removes droplets but cannot remove water vapor, so saturated gas may require additional conditioning before adsorption.

For chlorine-dioxide scrubbers, select packing and tower internals from the actual oxidizing chemical environment rather than assuming compatibility from HCl or chlorine service. ClO₂ concentration, temperature, liquid reaction products, cleaning chemistry, small hardware, demister materials, and long-term polymer exposure should all be reviewed before final selection.

When a packed odor scrubber removes H₂S but sulfur odor remains, identify residual reduced-sulfur compounds before adding packing. Mercaptans and other odorants may require different chemistry or a polishing stage. Gas analysis, scrubbing chemistry, oxidation conditions, liquid aging, demister carryover, and packed-bed contact should be evaluated separately.

When oxygen concentration increases in an SO₂ caustic scrubber, absorbed sulfur species may become more strongly oxidized, changing the sulfate/sulfite balance, dissolved-solids concentration, blowdown demand, crystallization behavior, distributor fouling, and demister deposits. Packing geometry affects fouling tolerance but does not replace liquid-chemistry control.