Wildfire smoke Possible
Daily PM2.5 peaked at 62.4 µg/m³ near Birmingham across 1 covered metro home to 1.2 million people. 1 metro placed a top-ten day in their record.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 4.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 5.2 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
Birmingham airport reported smoke and haze for three event-window hours. The independent FPA-FOD inventory records a substantial same-window cluster of nearby Alabama Forestry Commission wildfires, while the surface archive shows predominantly calm or light winds. Together they support wildfire smoke as a possible broad cause, but do not identify one contributing fire or quantify its PM2.5 share.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
USDA Forest Service Rocky Mountain Research Station hypothesis
FPA-FOD retains 12 Alabama Forestry Commission wildfire records discovered within 50 miles of Birmingham during the two-day smoke event, totaling 270.7 reported acres. The largest were 90 and 80 acres about 32-33 miles east of the airport on October 27 and a 76-acre fire about 36 miles away on October 28.
NOAA/NWS surface observations via Iowa Environmental Mesonet · Oct 28, 1999 hypothesis
BIRMINGHAM MUNI, 18.2 km from the PM2.5 target monitor, reported the official present-weather code FU (smoke) during 3 observed hours inside the catalog event window.
Inference, not direct attribution
surface_smoke_plus_bounded_fire_occurrences_possible.v1: This inference is recorded in the catalog methodology.
Evidence path
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.
Source or mechanism
surface_smoke_plus_bounded_fire_occurrences_possible.v1. This inference is recorded in the catalog methodology.
Air-mass movement
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.
Local response
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
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.
Birmingham-Hoover, AL
Monitor comparison window 1999-10-24 to 1999-10-31 · PM2.5 target: Wylam
39% above nearby days
55% higher than surrounding days
39% higher than surrounding days
55% higher than surrounding days
33% higher than surrounding days
40% higher than surrounding days
20% lower than 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.
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
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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Birmingham-Hoover, AL | 62.4 µg/m³ | 5.6 | Oct 27, 1999 | #6 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
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.
NOAA/NWS surface observations via Iowa Environmental Mesonet
BIRMINGHAM MUNI, 18.2 km from the PM2.5 target monitor, reported the official present-weather code FU (smoke) during 3 observed hours inside the catalog event window.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The surface code establishes smoke at the nearby airport; it does not identify whether the source was a wildfire, prescribed burn, agricultural fire, or another local fire.
USDA Forest Service Rocky Mountain Research Station
FPA-FOD retains 12 Alabama Forestry Commission wildfire records discovered within 50 miles of Birmingham during the two-day smoke event, totaling 270.7 reported acres. The largest were 90 and 80 acres about 32-33 miles east of the airport on October 27 and a 76-acre fire about 36 miles away on October 28.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
FPA-FOD is a fire-occurrence inventory, not a smoke-transport or PM2.5 source-apportionment product.
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.