Indiana Department of Environmental Management official
2024 PM2.5 exceptional-event demonstration, Part 2
IDEM lists October 20, 2024 Indianapolis PM2.5 monitors, including the West 18th Street 50.7 µg/m3 monitor, as impacted by wildfire smoke.
Wildfire smoke Documented
2024-10-20 wildfire smoke episode affecting Indianapolis-Carmel-Anderson, IN
Daily PM2.5 peaked at 50.7 µg/m³ near Indianapolis across 1 covered metro home to 2.2 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.7 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 3.7 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 “Wildfire smoke”
The supplied retained evidence supports wildfire smoke for this event; no supplied evidence establishes membership in a broader time-bounded episode.
Documented An agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
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
Wildfire smoke
IDEM lists October 20, 2024 Indianapolis PM2.5 monitors, including the West 18th Street 50.7 µg/m3 monitor, as impacted by wildfire smoke.
View supporting source ↗ - 2Research gap
Air-mass movement
The transport path has not been reconstructed
The retained record does not yet show how air traveled from the proposed source to these metros. A trajectory replay or dated plume analysis belongs here.
- 3Documented
Local response
50.7 µg/m³ near Indianapolis
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.3 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 “Wildfire smoke” explanation; it does not assign the cause by itself.
Indianapolis-Carmel-Anderson, IN
Monitor comparison window 2024-10-17 to 2024-10-23 · PM2.5 target: Indpls- W. 18th St./ Ernie Pyle School 90
56% above nearby days
About the same as surrounding days
29% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 27.3 µg/m³
56% higher than surrounding days
Before21.8 µg/m³ Event27.3 µg/m³ After11.6 µg/m³
PM10 53 µg/m³
29% higher than surrounding days
Before41 µg/m³ Event53 µg/m³ After40 µg/m³
Carbon monoxide 0.847 ppm
29% higher than surrounding days
Before0.874 ppm Event0.847 ppm After0.411 ppm
Nitrogen dioxide 16.4 ppb
About the same as surrounding days
Before16.6 ppb Event16.4 ppb After12 ppb
Sulfur dioxide 0.658 ppb
22% higher than surrounding days
Before0.537 ppb Event0.658 ppb After0.315 ppb
Ozone 0.034 ppm
27% higher than surrounding days
Before0.022 ppm Event0.034 ppm After0.035 ppm
Atmospheric conditions
Nearby EPA weather observationsAbout the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
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.
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.
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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 |
|---|---|---|---|---|
| Indianapolis-Carmel-Anderson, IN | 50.7 µg/m³ | 2.3 | Oct 20, 2024 | #23 of its top days |
"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.
Agency and publisher pages 1
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2024 PM2.5 exceptional-event demonstration, Part 2
IDEM lists October 20, 2024 Indianapolis PM2.5 monitors, including the West 18th Street 50.7 µg/m3 monitor, as impacted by wildfire smoke.
Status and provenance
Documented An agency or publisher page assesses this cause, without an agency record naming the event or an EPA qualifier on the data.
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.