Wildfire smoke Agency determination
Named sources Gray Fire 10,064 acres , WA · IRWIN 2023-WANES-001974 Ridge Creek Fire 4,474 acres , ID · IRWIN 2023-IDIPF-000447 Oregon Road Fire
Daily PM2.5 peaked at 239.7 µg/m³ near Spokane across 2 covered metros home to 4.8 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 ≈ 5.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 26 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 for this event. It is grouped with 1 other supplied event because the evidence identifies Canada as the shared origin and the affected intervals form one continuous 2023-08-19 through 2023-08-20 occurrence.
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 · Aug 19, 2023 official
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 48 PM2.5 samples in the candidate CBSA on 2023-08-19, 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.
U.S. EPA Air Quality System and the submitting air monitoring agency · Aug 20, 2023 official
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 48 PM2.5 samples in the candidate CBSA on 2023-08-20, 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.
U.S. EPA Air Quality System and the submitting air monitoring agency · Aug 20, 2023 official
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 240 PM2.5 samples in the candidate CBSA on 2023-08-20, 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.
See every retained source and limitation ↓
Sequence: Spokane (Aug 19) → Seattle (Aug 20)
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 (IF, Fire - Canadian.) on 48 PM2.5 samples in the candidate CBSA on 2023-08-19, identifying wildfire smoke as affecting the samples. An informational qualifier is an official…
View supporting source ↗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
The City of Spokane announced safer-air options because of heavy smoke on August 19.
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 2023-08-16 to 2023-08-23 · PM2.5 target: SPOKANE - MONROE ST
301% above nearby days
10% higher than surrounding days
279% higher than surrounding days
301% higher than surrounding days
279% higher than surrounding days
14% higher than surrounding days
About the same as surrounding days
10% higher than surrounding days
Seattle-Tacoma-Bellevue, WA
Monitor comparison window 2023-08-17 to 2023-08-23 · PM2.5 target: DARRINGTON - FIR ST (Darrington High School)
469% above nearby days
About the same as surrounding days
91% higher than surrounding days
469% higher than surrounding days
91% higher than surrounding days
38% higher than surrounding days
8% higher than surrounding days
11% higher than surrounding days
12% lower than surrounding days
About the same as surrounding days
5% higher 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 |
|---|---|---|---|---|
| Spokane-Spokane Valley, WA | 239.7 µg/m³ | 18.3 | Aug 19, 2023 | #4 of its top days |
| Seattle-Tacoma-Bellevue, WA | 89.4 µg/m³ | 4.1 | Aug 20, 2023 | #15 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 IF — Fire - Canadian.
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 48 PM2.5 samples in the candidate CBSA on 2023-08-19, 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.
AQS PM2.5 qualifier IF — Fire - Canadian.
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 48 PM2.5 samples in the candidate CBSA on 2023-08-20, 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.
AQS PM2.5 qualifier IF — Fire - Canadian.
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 240 PM2.5 samples in the candidate CBSA on 2023-08-20, 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, August 19, 2023
The multi-agency Spokane alerts explicitly attributed the episode to smoke from local and Canadian wildfires. IEM is the archive, not the official system of record.
Air Quality Report - August 2023
The regional clean-air agency attributes hazardous Spokane-area conditions on August 19–20 to widespread British Columbia fires and local Gray, Oregon Road, and Ridge Creek fires.
OEM - Wildfire Smoke and Air Quality Guidance
Seattle issued wildfire-smoke and air-quality guidance immediately before the August 20 event.
News Releases for Saturday, August 19, 2023
The City of Spokane announced safer-air options because of heavy smoke on August 19.
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.