The top five assignees together hold 35.2% of the 352 records in scope, and the top ten reach 50.6%. That means roughly half the field sits outside the ten most active filers, spread across ninety more ranked assignees and unranked entrants. The leader alone holds 31 records versus 21 at fifth place, so within the top group there is a clear front-runner rather than a tight cluster. For a new entrant, this points to a field where broad freedom-to-operate exists but the leading player's claims deserve specific scrutiny.

Filing peaked in 2019 at 29 records and has since settled into a plateau: the 2021-to-2024 comparison shows 17 down to 16, a -6% change over three years. That is a flattening, not a collapse. The 2025 and 2026 figures in any such dataset are understated because patent publication typically lags actual filing by around eighteen months, so recent years will fill in as more applications publish.

B01D, covering separation processes such as filtration, appears in 60.2% of the 352 records and is by far the dominant class. B01J (chemical and physical processes, including catalysis) follows at 17.9%, and C01B (non-metallic elements and inorganic compounds) at 8.8%. Smaller classes including C07F, F25J, C12M, C07C and C12P each sit under 9%, meaning the field is still framed mostly as separation-process hardware rather than as gas-liquefaction, bioreactor, or fermentation equipment. Because a single record can carry several IPC classes, these shares add up to more than 100% of the total.

US20240157326A1, filed by East China University of Science and Technology and published 2024-05-16, claims a packing element built from a collection-predistribution unit, a fluid uniform distribution unit and an opening window unit arranged in sequence. Its specific claim elements include orifices sized 1-5 mm on the distribution substrate and a window-length-to-fluid-viscosity relationship tied to a 0.5 power. Anyone designing a structured packing element with orifice geometry or viscosity-scaled window sizing in that same numeric range should review this filing closely, though contactor designs using different geometric ratios or distribution mechanisms would sit outside its specific claim language.

The clearest gaps sit in the IPC classes with the lowest density relative to the dominant B01D cluster: C12M (bioreactor and enzyme apparatus) and C12P (fermentation and enzymatic synthesis) each cover under 7% of the 352 records despite touching gas-exchange hardware that overlaps contactor design. Dust fouling mitigation and wind-driven contactor orientation control are also underrepresented relative to their operational importance in field-deployed direct air capture units. These are areas where a well-drafted first claim has more room to stand without colliding with the dense B01D prior art.