The assignee ranking spans 100 companies counted by patent family, with the leader holding 488 records out of 13,551 in scope. The field is fragmented rather than gated: the top 10 assignees combined account for only 13.9% of all records, so no single company controls the space. Several of the most active historical filers have slowed sharply in the most recent year, though publication lag means some of that recent-year drop reflects filings still working through the pipeline rather than an actual stop in R&D.

On the last complete years of data, filing activity has eased: 2021 to 2024 saw a 20% decline, from 505 to 406 records, after a peak of 612 records in 2023. The 2025 and 2026 figures in the trend are understated because publication typically lags actual filing by around 18 months, so they should not be read as continuing the same downward slope. The honest read is that the field passed a filing peak in 2023 and has since cooled, pending confirmation once later years finish publishing.

The search scope combines thermal Heating, HVAC thermal Heating and thermal Ventilation terms with core thermal-management concepts including temperature sensors, heat flux, thermal cycles, working fluid, heat transfer and refrigerant circuits. This pulls in more than conventional building HVAC hardware — the two largest IPC classes are A61B (diagnosis & surgery, 17.0% of records) and A61N (electrotherapy, 8.6%), both ahead of H05B electric heating circuits at 5.4%. Anyone scoping a building-systems portfolio should expect adjacent medical thermal-sensing filings to surface in the same search.