Wildfire smoke Agency determination
Daily PM2.5 peaked at 85.9 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 ≈ 3.6 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 2.2 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
Supplied qualified evidence supports wildfire-smoke as the root cause. The grouping includes only events linked by explicit shared episode evidence; otherwise this remains a single-event episode.
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 · Jul 31, 2021 official
EPA AQS carries an agency-submitted informational qualifier (IT, Wildfire-U. S.) on 144 PM2.5 samples in the candidate CBSA on 2021-07-31, 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 Clean Air Agency official
Spokane Regional Clean Air Agency states that wildfire smoke on July 31 and August 1 caused exceedances of the 24-hour PM2.5 health standard.
National Weather Service via Iowa Environmental Mesonet archive · Jul 30, 2021 corroborates
An archived NWS Air Quality Alert for Spokane-Spokane Valley, WA, issued 2021-07-30T19:13Z, explicitly identifies wildfire smoke. 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 144 PM2.5 samples in the candidate CBSA on 2021-07-31, 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
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 3.9 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 2021-07-28 to 2021-08-03 · PM2.5 target: Colville-E 1St
22% above nearby days
147% higher than surrounding days
30% higher than surrounding days
22% higher than surrounding days
30% higher than surrounding days
16% higher than surrounding days
6% higher than surrounding days
147% 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 | 85.9 µg/m³ | 3.9 | Jul 31, 2021 | #24 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 144 PM2.5 samples in the candidate CBSA on 2021-07-31, 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.
An archived NWS Air Quality Alert for Spokane-Spokane Valley, WA, issued 2021-07-30T19:13Z, explicitly identifies wildfire smoke. IEM is the archive, not the official system of record.
Weekend wildfire smoke results in air quality over health standard; Air Quality Alert issued
Spokane Regional Clean Air Agency states that wildfire smoke on July 31 and August 1 caused exceedances of the 24-hour PM2.5 health standard.
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.