Wildfire smoke Agency determination
Daily PM2.5 peaked at 103.5 µg/m³ near Spokane across 1 covered metro home to 604,962 people.
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 ≈ 2.6 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
Qualified supplied evidence supports wildfire smoke as the root cause of this event. The supplied record does not establish a coherent shared occurrence with neighboring candidates, so the episode remains event-specific.
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
U.S. EPA Air Quality System and the submitting air monitoring agency · Sep 12, 2022 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 48 PM2.5 samples in the candidate CBSA on 2022-09-12, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
Spokane Regional Health District · Sep 12, 2022 official
The Spokane Regional Health District reported on September 12 that smoke drifting from area wildfires was affecting Spokane air quality and could worsen under high pressure.
Washington, Idaho, tribal, and Spokane air agencies via NWS · Sep 12, 2022 corroborates
The multi-agency Spokane alert explicitly identified wildfire smoke during the September 12 particle-pollution event. IEM is the archive, not the official system of record.
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
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 48 PM2.5 samples in the candidate CBSA on 2022-09-12, identifying wildfire smoke as affecting the samples. An informational qualifier is an official…
View supporting source ↗Air-mass movement
The Spokane Regional Health District reported on September 12 that smoke drifting from area wildfires was affecting Spokane air quality and could worsen under high pressure.
View transport source ↗Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 4.7 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.
Spokane-Spokane Valley, WA
Monitor comparison window 2022-09-09 to 2022-09-15 · PM2.5 target: Spokane Valley-E Broadway Ave
61% above nearby days
65% higher than surrounding days
88% higher than surrounding days
61% higher than surrounding days
88% higher than surrounding days
About the same as surrounding days
5% higher than surrounding days
65% higher than 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 |
|---|---|---|---|---|
| Spokane-Spokane Valley, WA | 103.5 µg/m³ | 4.7 | Sep 12, 2022 | #21 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.
AQS PM2.5 qualifier IT — Wildfire-U. S.
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 48 PM2.5 samples in the candidate CBSA on 2022-09-12, identifying wildfire smoke as affecting the samples. An informational qualifier is an official submitting-agency flag, not a request for exclusion or an EPA-concurred determination.
Archived Spokane Air Quality Alert, September 12, 2022
The multi-agency Spokane alert explicitly identified wildfire smoke during the September 12 particle-pollution event. IEM is the archive, not the official system of record.
The Spokane Regional Health District reported on September 12 that smoke drifting from area wildfires was affecting Spokane air quality and could worsen under high pressure.
Air quality in Spokane reaches very unhealthy Monday as smoke blankets area
Contemporaneous local reporting says smoke from multiple fires in Washington, Idaho, and Montana was funneled into Spokane and drove unhealthy to very unhealthy air quality.
Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.
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.