NOAA Satellite Services Division corroborates
Smoke analysis through 1500 UTC October 19, 2005
NOAA observed Southeast haze and said residual smoke from numerous primarily agricultural fires could be trapped below the inversion under a surface high.
Prescribed fire Possible
2005-10-19 Nashville-Davidson--Murfreesboro--Franklin, TN prescribed-fire smoke episode
Daily PM2.5 peaked at 61.1 µg/m³ near Nashville across 1 covered metro home to 2.2 million people. 1 metro recorded their worst day on record.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.3 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 4.9 million cigarettes. An awareness illustration of outdoor exposure at 22 µg/m³ per cigarette (Berkeley Earth), counting only the event's ranked days; not a medical dose.
Why we think this happened
The basis for “Prescribed fire”
NOAA described exact-day Southeast haze that could contain residual smoke from numerous primarily agricultural fires beneath an inversion.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
NASA Earth Observatory · Oct 19, 2005 corroborates
Fires in the Southern United States
NASA's October 18 satellite image shows numerous fires across the South with visible smoke plumes, and its October 19 account says the mix included prescribed burns conducted by land managers.
Evidence path
From source to city
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
- 1Documented
Source or mechanism
Prescribed fire
NOAA observed Southeast haze and said residual smoke from numerous primarily agricultural fires could be trapped below the inversion under a surface high.
View supporting source ↗ - 2Documented
Air-mass movement
Transport into the affected region is documented
NOAA observed Southeast haze and said residual smoke from numerous primarily agricultural fires could be trapped below the inversion under a surface high.
View transport source ↗ - 3Documented
Local response
61.1 µg/m³ near Nashville
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.8 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓
Event autopsy
What the instruments saw
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Prescribed fire” explanation; it does not assign the cause by itself.
Nashville-Davidson--Murfreesboro--Franklin, TN
Monitor comparison window 2005-10-16 to 2005-10-22 · PM2.5 target: Columbia
13% above nearby days
No adjacent-day comparison
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 22.2 µg/m³
13% higher than surrounding days
Before10.3 µg/m³ Event22.2 µg/m³ After19.6 µg/m³
PM10 46 µg/m³
No adjacent-day comparison
Before— Event46 µg/m³ After—
Carbon monoxide 1.24 ppm
58% higher than surrounding days
Before0.785 ppm Event1.24 ppm After0.717 ppm
Nitrogen dioxide 36.2 ppb
6% higher than surrounding days
Before34.5 ppb Event36.2 ppb After14.8 ppb
Sulfur dioxide 4.38 ppb
9% higher than surrounding days
Before4.08 ppb Event4.38 ppb After2.79 ppb
Ozone 0.034 ppm
16% higher than surrounding days
Before0.029 ppm Event0.034 ppm After0.022 ppm
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
Air-mass reconstruction
Where the air had been
NOAA HYSPLIT traces the air arriving at each metro backward for 72 hours. Multiple arrival times and heights show whether the broad path is stable—or sensitive to assumptions about when and where the polluted layer arrived.
Air arriving near Nashville-Davidson--Murfreesboro--Franklin
Peak-date arrivals · 2005-10-19
Broad history Mostly west of the metro
72-hour reach 150–1,950 km
Sensitivity runs 12 modeled paths
Near surface · 100 mLower atmosphere · 500 mHigher layer · 1,000 m
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Measured daily PM2.5 at EPA monitors, as cigarette-equivalents
EPA monitors sit in metro areas, so the colour clusters there. Land between and beyond
them is unmeasured, not clean: this map shows where IAQng has readings, not the extent
of the smoke.
—
Episode peak
-- cigarettes
The smoke map's scale, replayed over this event: the surface interpolates between covered metros' daily records, framed to the affected region. Hover for a reading, click a metro to pin it to the card. Days a monitor did not report draw nothing.
Views from the selected metro
Camera views near
Select a metro on the map to see nearby cameras. Where an operator archive reaches the event, drag the divider to compare two moments, adjust either date and time, or play the available event-day frames. Camera imagery is visual context, not an air-quality measurement or proof of smoke.
No useful public camera views are currently available within 80 km of this metro.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Nashville-Davidson--Murfreesboro--Franklin, TN | 61.1 µg/m³ | 2.8 | Oct 19, 2005 | Worst day on record |
"Cigarettes, whole event" totals a metro's ranked event days at 22 µg/m³ per cigarette: what a person outdoors there breathed across the event, as the illustration. "All-time standing" is where this episode's days sit in each metro's ranked record (worst-area measure, since 1999). Full local context is on each metro's Air Records page.
Public evidence library
What supports this account
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
Fires in the Southern United States
NASA Earth Observatory
NASA's October 18 satellite image shows numerous fires across the South with visible smoke plumes, and its October 19 account says the mix included prescribed burns conducted by land managers.
What it supports
A retained source supports the event interpretation for the stated place and dates.
Limit
The regional image does not identify which individual fires affected Nashville at ground level; the retained NOAA analysis supplies the closer transport assessment.
Smoke analysis through 1500 UTC October 19, 2005
NOAA Satellite Services Division
NOAA observed Southeast haze and said residual smoke from numerous primarily agricultural fires could be trapped below the inversion under a surface high.
What it supports
A retained source supports the attributed cause for the stated place and dates.
Limit
The analyst used conditional language and did not identify Nashville surface measurements.
What remains uncertain
- Conditional regional attribution is capped at possible.
Status and provenance
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.