area_classification string | definition_heading string | derived_fields list | id string | pollutant string | row_id string | source string | source_quote string | test string | threshold_tpy string | url string | verified_fields list |
|---|---|---|---|---|---|---|---|---|---|---|---|
Serious | Major source means any stationary source | [
"row_id",
"test"
] | co-nonattainment-serious | carbon monoxide | co-nonattainment-serious | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For carbon monoxide nonattainment areas: (A) That are classified or treated as classified as “Serious,” and (B) in which stationary sources contribute significantly to carbon monoxide levels as determined under rules issued by the Administrator, sources with the potential to emit 50 tpy or more of carbon monoxide; and | Part D Title I nonattainment major stationary source | 50 | https://referencesource.org/clean-air-act-major-source-thresholds/co-nonattainment-serious/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
Extreme | Major source means any stationary source | [
"row_id",
"test"
] | ozone-nonattainment-voc-nox-extreme | volatile organic compounds or oxides of nitrogen | ozone-nonattainment-voc-nox-extreme | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For ozone nonattainment areas, sources with the potential to emit 100 tpy or more of volatile organic compounds or oxides of nitrogen in areas classified or treated as classified as “Marginal” or “Moderate,” 50 tpy or more in areas classified or treated as classified as “Serious,” 25 tpy or more in areas classified or ... | Part D Title I nonattainment major stationary source | 10 | https://referencesource.org/clean-air-act-major-source-thresholds/ozone-nonattainment-voc-nox-extreme/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
Marginal | Major source means any stationary source | [
"row_id",
"test"
] | ozone-nonattainment-voc-nox-marginal | volatile organic compounds or oxides of nitrogen | ozone-nonattainment-voc-nox-marginal | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For ozone nonattainment areas, sources with the potential to emit 100 tpy or more of volatile organic compounds or oxides of nitrogen in areas classified or treated as classified as “Marginal” or “Moderate,” 50 tpy or more in areas classified or treated as classified as “Serious,” 25 tpy or more in areas classified or ... | Part D Title I nonattainment major stationary source | 100 | https://referencesource.org/clean-air-act-major-source-thresholds/ozone-nonattainment-voc-nox-marginal/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
Moderate | Major source means any stationary source | [
"row_id",
"test"
] | ozone-nonattainment-voc-nox-moderate | volatile organic compounds or oxides of nitrogen | ozone-nonattainment-voc-nox-moderate | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For ozone nonattainment areas, sources with the potential to emit 100 tpy or more of volatile organic compounds or oxides of nitrogen in areas classified or treated as classified as “Marginal” or “Moderate,” 50 tpy or more in areas classified or treated as classified as “Serious,” 25 tpy or more in areas classified or ... | Part D Title I nonattainment major stationary source | 100 | https://referencesource.org/clean-air-act-major-source-thresholds/ozone-nonattainment-voc-nox-moderate/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
Serious | Major source means any stationary source | [
"row_id",
"test"
] | ozone-nonattainment-voc-nox-serious | volatile organic compounds or oxides of nitrogen | ozone-nonattainment-voc-nox-serious | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For ozone nonattainment areas, sources with the potential to emit 100 tpy or more of volatile organic compounds or oxides of nitrogen in areas classified or treated as classified as “Marginal” or “Moderate,” 50 tpy or more in areas classified or treated as classified as “Serious,” 25 tpy or more in areas classified or ... | Part D Title I nonattainment major stationary source | 50 | https://referencesource.org/clean-air-act-major-source-thresholds/ozone-nonattainment-voc-nox-serious/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
Severe | Major source means any stationary source | [
"row_id",
"test"
] | ozone-nonattainment-voc-nox-severe | volatile organic compounds or oxides of nitrogen | ozone-nonattainment-voc-nox-severe | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For ozone nonattainment areas, sources with the potential to emit 100 tpy or more of volatile organic compounds or oxides of nitrogen in areas classified or treated as classified as “Marginal” or “Moderate,” 50 tpy or more in areas classified or treated as classified as “Serious,” 25 tpy or more in areas classified or ... | Part D Title I nonattainment major stationary source | 25 | https://referencesource.org/clean-air-act-major-source-thresholds/ozone-nonattainment-voc-nox-severe/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
ozone transport region | Major source means any stationary source | [
"row_id",
"test"
] | ozone-transport-region-voc | volatile organic compounds | ozone-transport-region-voc | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For ozone transport regions established pursuant to section 184 of the Act, sources with the potential to emit 50 tpy or more of volatile organic compounds; | Part D Title I nonattainment major stationary source | 50 | https://referencesource.org/clean-air-act-major-source-thresholds/ozone-transport-region-voc/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
Serious | Major source means any stationary source | [
"row_id",
"test"
] | pm10-nonattainment-serious | PM-10 | pm10-nonattainment-serious | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For particulate matter (PM-10) nonattainment areas classified or treated as classified as “Serious,” sources with the potential to emit 70 tpy or more of PM-10. | Part D Title I nonattainment major stationary source | 70 | https://referencesource.org/clean-air-act-major-source-thresholds/pm10-nonattainment-serious/ | [
"area_classification",
"pollutant",
"threshold_tpy"
] |
null | Major stationary source means | [
"row_id",
"test"
] | psd-any-other-source-250tpy | a regulated NSR pollutant | psd-any-other-source-250tpy | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-52/subpart-A/section-52.21 | Notwithstanding the stationary source size specified in paragraph (b)(1)(i)(a) of this section, any stationary source which emits, or has the potential to emit, 250 tons per year or more of a regulated NSR pollutant; or | PSD major stationary source (40 CFR 52.21) — any other source category | 250 | https://referencesource.org/clean-air-act-major-source-thresholds/psd-any-other-source-250tpy/ | [
"pollutant",
"threshold_tpy"
] |
null | Major stationary source means | [
"row_id",
"test"
] | psd-listed-source-category-100tpy | any regulated NSR pollutant | psd-listed-source-category-100tpy | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-52/subpart-A/section-52.21 | Any of the following stationary sources of air pollutants which emits, or has the potential to emit, 100 tons per year or more of any regulated NSR pollutant: Fossil fuel-fired steam electric plants of more than 250 million British thermal units per hour heat input, coal cleaning plants (with thermal dryers), kraft pul... | PSD major stationary source (40 CFR 52.21) — one of the listed source categories | 100 | https://referencesource.org/clean-air-act-major-source-thresholds/psd-listed-source-category-100tpy/ | [
"pollutant",
"threshold_tpy"
] |
null | Major source means any stationary source | [
"row_id",
"test"
] | section112-combined-hap | any combination of such hazardous air pollutants | section112-combined-hap | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For pollutants other than radionuclides, any stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit, in the aggregate, 10 tons per year (tpy) or more of any hazardous air pollutant which has been listed pursuant to section 112(b... | Section 112 HAP major source | 25 | https://referencesource.org/clean-air-act-major-source-thresholds/section112-combined-hap/ | [
"pollutant",
"threshold_tpy"
] |
null | Major source means any stationary source | [
"row_id",
"test"
] | section112-radionuclides | radionuclides | section112-radionuclides | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For radionuclides, “major source” shall have the meaning specified by the Administrator by rule. | Section 112 HAP major source | specified by the Administrator by rule | https://referencesource.org/clean-air-act-major-source-thresholds/section112-radionuclides/ | [
"pollutant",
"threshold_tpy"
] |
null | Major source means any stationary source | [
"row_id",
"test"
] | section112-single-hap | any hazardous air pollutant which has been listed pursuant to section 112(b) of the Act | section112-single-hap | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | For pollutants other than radionuclides, any stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit, in the aggregate, 10 tons per year (tpy) or more of any hazardous air pollutant which has been listed pursuant to section 112(b... | Section 112 HAP major source | 10 | https://referencesource.org/clean-air-act-major-source-thresholds/section112-single-hap/ | [
"pollutant",
"threshold_tpy"
] |
null | Major source means any stationary source | [
"row_id",
"test"
] | section302-any-regulated-pollutant | any air pollutant subject to regulation | section302-any-regulated-pollutant | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | A major stationary source of air pollutants, as defined in section 302 of the Act, that directly emits, or has the potential to emit, 100 tpy or more of any air pollutant subject to regulation (including any major source of fugitive emissions of any such pollutant, as determined by rule by the Administrator). | Section 302 major stationary source (Title V, 40 CFR 70.2) | 100 | https://referencesource.org/clean-air-act-major-source-thresholds/section302-any-regulated-pollutant/ | [
"pollutant",
"threshold_tpy"
] |
null | Major source means any stationary source | [
"row_id",
"test"
] | section302-ghg-co2e | Greenhouse gases (GHGs) | section302-ghg-co2e | https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2 | Greenhouse gases (GHGs), the air pollutant defined in § 86.1818-12(a) of this chapter as the aggregate group of six greenhouse gases: carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, shall not be subject to regulation unless, as of July 1, 2011, the GHG emissions ar... | Section 302 major stationary source (Title V, 40 CFR 70.2) — greenhouse-gas ‘subject to regulation’ threshold | 100,000 | https://referencesource.org/clean-air-act-major-source-thresholds/section302-ghg-co2e/ | [
"pollutant",
"threshold_tpy"
] |
Clean Air Act "major source" emission thresholds by pollutant and area classification
Canonical, always-current version: https://referencesource.org/clean-air-act-major-source-thresholds/ Machine-readable: https://referencesource.org/clean-air-act-major-source-thresholds/data.json — this mirror is a point-in-time copy.
- Last verified: 2026-08-31
- Stale after: 2027-08-31 (past this date, prefer the canonical copy — it re-verifies on a cadence this snapshot does not)
- Records: 15
Whether a stationary source (a factory, plant, or facility) needs a federal Clean Air Act permit turns on whether its potential to emit crosses a tons-per-year (tpy) threshold -- and 'major source' is not one number but several, set by different regulations that do not agree. The Title V definition at 40 CFR 70.2 alone carries three overlapping tests: the section 112 hazardous-air-pollutant test (10 tpy of a single HAP, 25 tpy of any combination), the section 302 test (100 tpy of any air pollutant subject to regulation, with greenhouse gases counting only at 100,000 tpy CO2 equivalent), and the part D title I nonattainment test, tiered by pollutant (VOC, NOx, CO, PM-10) and by how severely out of attainment the area is (ozone precursors at 100 tpy in Marginal or Moderate areas, 50 in Serious, 25 in Severe, 10 in Extreme). PSD is a separate definition in a separate part -- 40 CFR 52.21(b)(1)(i) -- and it splits again: 100 tpy for the source categories the rule lists by name, 250 tpy for everything else. That last distinction is the one most often flattened: a facility told 'the threshold is 100 tons a year' is being given the Title V number, which is the wrong answer for any source outside the listed categories. Each record is one test/pollutant/classification combination and the threshold that test sets, quoted from the regulation that sets it. Answers 'what's the major-source threshold for VOC in a Severe ozone nonattainment area', 'does 25 tpy of a HAP make me major', and 'is my PSD threshold 100 or 250 tons a year'.
Provenance — what every record carries
Every record carries source (the URL the value was read from) and
source_quote (a verbatim quote from that page stating it). A value you
cannot check against its page is indistinguishable from an invented one;
these can all be checked. Each record is also individually addressable on
the canonical site at its url.
Licence position
US federal regulation — 17 USC 105, no copyright
Facts are not copyrightable; what this dataset takes from each source is a fact plus a short attributed quote linking back to the page that states it.
Sources
- https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-70/subpart-A/section-70.2
- https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-52/subpart-A/section-52.21
Fields
See any record in data/records.jsonl — field names are self-describing,
and the canonical page for each record renders them with labels:
https://referencesource.org/clean-air-act-major-source-thresholds/
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