A packed NOx scrubber should distinguish nitric oxide from nitrogen dioxide rather than using total NOx alone. If the inlet is dominated by poorly absorbed NO, oxidation chemistry may control performance more strongly than packing surface area. NO/NO₂ ratio, absorbent chemistry, oxidation strategy, materials, liquid salts, circulation, and packed height should be evaluated together.

In a pressurized biogas water scrubber, stronger gas-liquid contact can improve CO₂ removal but does not eliminate methane dissolution. Pressure, water circulation, packing efficiency, flash recovery, water regeneration, H₂S loading, pressure drop, outlet CO₂, and methane-recovery target should be optimized together.

When a limestone-slurry FGD project proposes fine random packing for higher SO₂ removal, first evaluate solids concentration, gypsum formation, scale, support-grid plugging, abrasion, washing, and acceptable maintenance interval. Fine high-area packing can become a solids trap, and in heavy slurry service an open spray-contacting system may be more suitable than forcing the duty into a conventional packed bed.

For a seawater SO₂ scrubber, high circulation rate alone does not guarantee adequate removal. Natural alkalinity, pH, temperature, salinity, fresh-water dilution, recirculation fraction, fouling, material compatibility, and demister salt carryover should be included in the operating basis. The limiting factor may be chemical buffering rather than packing hydraulics.

Outdoor scrubbers with open vertical stacks should be reviewed for rain ingress, especially during shutdown. Rainwater can wet the demister from above, increase sump level, dilute reagent, load distributors and packing, and create restart carryover. Stack termination, drainage, storm liquid balance, and restart checks should be considered before blaming mist-eliminator performance.