Wildfire smoke Agency determination
Daily PM2.5 peaked at 185 µg/m³ near Spokane across 1 covered metro home to 604,962 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 ≈ 14.6 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 8.8 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 frozen evidence supports wildfire smoke as the broad cause for this time-bounded 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 · Aug 19, 2018 official
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 24 PM2.5 samples in the candidate CBSA on 2018-08-19, 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, 2018 official
EPA AQS carries an agency-submitted informational qualifier (IF, Fire - Canadian.) on 24 PM2.5 samples in the candidate CBSA on 2018-08-20, 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.
Spokane Regional Clean Air Agency · Aug 1, 2018 official
The regional air agency attributes widespread and heavy August 2018 smoke to wildfires in British Columbia, Washington, Oregon, Idaho, Montana, and California.
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 24 PM2.5 samples in the candidate CBSA on 2018-08-19, identifying wildfire smoke as affecting the samples. An informational qualifier is an official…
View supporting source ↗Air-mass movement
NOAA HYSPLIT modeled 12 backward paths across multiple arrival times and heights. They show where the air traveled, not which source polluted it.
Explore the modeled paths ↓Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 8.4 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 2018-08-16 to 2018-08-23 · PM2.5 target: SPOKANE - MONROE ST
231% above nearby days
45% higher than surrounding days
154% higher than surrounding days
231% higher than surrounding days
154% higher than surrounding days
32% lower than surrounding days
7% lower than surrounding days
45% 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.
Air-mass reconstruction
NOAA HYSPLIT traces the air arriving at each metro backward for 72 hours. Multiple arrival times and heights show whether the broad path is stable—or sensitive to assumptions about when and where the polluted layer arrived.
Air arriving near Spokane-Spokane Valley
Peak-date arrivals · 2018-08-19
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
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 | 185 µg/m³ | 15.2 | Aug 19, 2018 | #9 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 24 PM2.5 samples in the candidate CBSA on 2018-08-19, 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 24 PM2.5 samples in the candidate CBSA on 2018-08-20, 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.
An archived NWS Air Quality Alert for Spokane-Spokane Valley, WA, issued 2018-08-19T19:43Z, explicitly identifies wildfire smoke. IEM is the archive, not the official system of record.
NWS Dense Smoke record, OKANOGAN HIGHLANDS, WASHINGTON (2018-08-03)
An air quality sensor in Inchelium recorded periods of Unhealthy air quality due to smoke from area wildfires through much of August.
NWS Dense Smoke record, MOSES LAKE AREA, WASHINGTON (2018-08-19)
An air quality sensor in Quincy recorded generally Unhealthy air quality with occasional spikes into the Very Unhealthy and Hazardous range from August 19th through the 21st as smoke from regional wildfires blew into the region.
NWS Dense Smoke record, OKANOGAN HIGHLANDS, WASHINGTON (2018-08-03)
An air quality sensor in Nespelem recorded periods of Unhealthy air quality due to smoke from area wildfires through much of August.
NWS Dense Smoke record, OKANOGAN HIGHLANDS, WASHINGTON (2018-08-03)
An air quality sensor in Republic recorded almost continuous Unhealthy air quality due to smoke from area wildfires through much of August.
NWS Dense Smoke record, MOSES LAKE AREA, WASHINGTON (2018-08-20)
An air quality sensor in Moses Lake recorded generally Unhealthy air quality with a brief peak into the Very Unhealthy range from August 20th through the 21st as smoke from regional wildfires blew into the region.
NWS Dense Smoke record, EAST SLOPES NORTHERN CASCADES, WASHINGTON (2018-08-03)
An air quality sensor at Twisp recorded Unhealthy air quality from August 3rd through August 27th with occasional spikes into the Hazardous category.
NWS Dense Smoke record, NORTHEAST MOUNTAINS, WASHINGTON (2018-08-03)
An air quality sensor in Colville recorded occasional periods of Unhealthy air quality with a few spikes into the Very Unhealthy range due to smoke from area wildfires through much of August.
NWS Dense Smoke record, SPOKANE AREA, WASHINGTON (2018-08-16)
The air quality sensors in the Spokane area recorded generally Unhealthy air quality with a period of Hazardous air quality during the second and third weeks of August as smoke from regional wildfires infiltrated the region.
NWS Dense Smoke record, OKANOGAN VALLEY, WASHINGTON (2018-08-03)
The air quality sensor at Omak recorded Unhealthy air quality through most of the month of August.
NWS Dense Smoke record, EAST SLOPES NORTHERN CASCADES, WASHINGTON (2018-08-03)
An air quality sensor at Winthrop recorded Unhealthy air quality from August 3rd through August 27th with occasional spikes into the Very Unhealthy category.
NWS Dense Smoke record, WENATCHEE AREA, WASHINGTON (2018-08-19)
An air quality sensor in Wenatchee recorded a period of Unhealthy to Hazardous air quality during the third week of August.
Air Quality Report: August 2018
The regional air agency attributes widespread and heavy August 2018 smoke to wildfires in British Columbia, Washington, Oregon, Idaho, Montana, and California.
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.