The dataset ranks 100 assignees by patent family count, and the leading assignee holds 208 records with the field dropping to 97 by fifth place and 83 by tenth. That is a fragmented landscape rather than one dominated by a single company: the top five assignees combined account for only 9.0% of the 7,417 records in scope. Anyone doing freedom-to-operate work in this space needs to check a long list of mid-sized holders, not just the largest filer.

Filing activity rose from 252 records in 2017 to a peak of 606 in 2021, almost certainly reflecting pandemic-era demand for indoor air filtration. It then declined to 236 by 2024, a -61% change over that three-year span, which is the most recent period the data can treat as complete. 2025 and 2026 figures look lower still, but that reflects the roughly 18-month lag between filing and publication rather than a genuine collapse in R&D activity.

B01D, the separation-processes class covering filter media and mechanical filtration, is the core of the field at 43.5% of the 7,417 records. F24F (air conditioning and ventilation) follows at 16.0%, but sterilising equipment (A61L), body-fluid devices (A61M), material testing (G01N), cleaning appliances (A47L), rescue equipment (A62B) and catalysis-linked processes (B01J) each carry a meaningful share too. A record can sit in several of these classes at once, so a search limited to F24F alone will miss a large share of relevant filings.

US20260102637A1 is a 2026 filing from Patient Knowhow, Inc. covering a maskless respiratory, skin and eye protection device that pairs a filter and fan sized for a stated aerosol filtration efficiency threshold around 0.3 micron particles, plus filtration of named chemical warfare agent vapors. Its claims are narrow to that combined aerosol-and-vapor threshold and device form factor, so it constrains designs that match both elements closely rather than blocking HEPA filtration broadly. Filers working on general HVAC or appliance filtration are unlikely to be affected by this specific claim scope.

The dense claim territory sits in core filter media and air-conditioning housings (B01D and F24F), where filing density is highest. Sub-areas tied to specific test methodologies and performance metrics — penetrating particle size measurement, filter loading and dust-holding capacity, media pleating geometry aimed at pressure drop, and clean air delivery rate measurement — carry the underlying language but drew comparatively few dedicated filings, making them worth a closer look before assuming the space is occupied.