Pennsylvania DEP official
Ambient Air Quality Update
The agency presentation states that the February 2-4, 2019 PM2.5 episode occurred with cloud cover, light winds, and a strong inversion.
Temperature inversion Likely
2019-02-03 to 2019-02-04 Harrisburg-Carlisle, PA temperature-inversion pollution episode
Daily PM2.5 peaked at 55.4 µg/m³ near Harrisburg across 1 covered metro home to 615,361 people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 4.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 2.5 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 “Temperature inversion”
A Pennsylvania DEP presentation identifies the exact February 2-4, 2019 PM2.5 episode and attributes it to cloud cover, light winds, and a strong inversion.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
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
Temperature inversion
The agency presentation states that the February 2-4, 2019 PM2.5 episode occurred with cloud cover, light winds, and a strong inversion.
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
55.4 µg/m³ near Harrisburg
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.5 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 “Temperature inversion” explanation; it does not assign the cause by itself.
Harrisburg-Carlisle, PA
Monitor comparison window 2019-01-31 to 2019-02-07 · PM2.5 target: Carlisle
90% above nearby days
52% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 46.1 µg/m³
90% higher than surrounding days
Before14.8 µg/m³ Event46.1 µg/m³ After16.6 µg/m³
PM10 36.5 µg/m³
52% higher than surrounding days
Before24 µg/m³ Event36.5 µg/m³ After11 µg/m³
Ozone 0.008 ppm
16% lower than surrounding days
Before0.011 ppm Event0.008 ppm After0.010 ppm
Atmospheric conditions
Nearby EPA weather observationsAbout 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 |
|---|---|---|---|---|
| Harrisburg-Carlisle, PA | 55.4 µg/m³ | 5.0 | Feb 3, 2019 | #19 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.
Ambient Air Quality Update
Pennsylvania DEP
The agency presentation states that the February 2-4, 2019 PM2.5 episode occurred with cloud cover, light winds, and a strong inversion.
What it supports
An official source supports the attributed cause for the stated place and dates.
What remains uncertain
- The classification is bounded to the retained evidence and does not apportion every source contributing to the daily PM2.5 value.
Status and provenance
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
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.