One assignee holds 54 of the 360 records in scope, making it the clear leader in this dataset, with the next four ranked entrants bringing the top five combined to 107 records, or 29.7% of the field. Beyond the top ten — which together hold 40.3% of records — filings spread thinly across the remaining ranked assignees. This pattern, a strong single leader followed by a moderate long tail, means competitive tracking should focus first on the leader's portfolio and then on watching which smaller filers start accumulating multiple records rather than single filings.

Over the clean three-year comparison from 2021 to 2024, filings fell 69%, following a peak of 17 records in 2020. That said, patent publication typically lags filing by around 18 months, so the lower counts shown for 2025 and 2026 are provisional and will rise as more records publish. The honest read is a cooling trend through 2024, not a confirmed continued decline into the most recent years.

No single IPC class dominates outright: non-metallic elements and inorganic compounds (C01B) and gasification of fuels (C10J) are tied at 17.2% of the 360 records each, with earth and rock drilling (E21B) close behind at 16.9%. Because a single patent record can carry multiple IPC classes, these percentages add up to more than 100% and should not be read as mutually exclusive categories. The practical takeaway is that plasma heating claims cut across waste treatment, hydrocarbon recovery, and catalytic processing rather than sitting in one vertical.

The United States receives the largest share of filings among receiving offices tracked, at 96 records, followed by South Korea at 42 and WIPO PCT filings at 37. Europe, India and Australia each sit in a similar band from the high 20s to low 30s. This spread indicates that meaningful protection in this field typically requires a multi-jurisdiction strategy rather than reliance on a single national filing.

US5505909A, filed via PCT in 1991 and published in 1996, covers a process and device that mixes plasma gas flow into hot flue gas from waste incinerators to thermally decompose toxic compounds, with pre-heating of the fresh flue gas through a recuperation-stage heat exchanger working in counter-flow against the plasma-treated gas. It is one of the earliest records in this dataset combining plasma injection with heat recuperation for emissions treatment, so its claims are most relevant to designs that use this specific recuperative counter-flow arrangement for incinerator flue gas. Designs using different heat-exchange geometries, different plasma injection points, or entirely different target gas streams sit outside its core claim scope, but a claim-by-claim comparison against the granted claim set is needed before relying on that distinction.