Wildfire smoke
Wildfire-smoke episode, 2018-08-20 through 2018-08-22
Daily PM2.5 peaked at 55.4 µg/m³ near Denver across 2 covered metros home to 3.8 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 ≈ 2.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 9.2 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.
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.
What happened, in the record
Qualified frozen evidence supports wildfire smoke as the broad cause for this time-bounded episode.
Sequence: Denver (Aug 20) → Colorado Springs (Aug 20)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Denver-Aurora-Lakewood, CO | 55.4 µg/m³ | 2.5 | Aug 20, 2018 | #12 of its top days |
| Colorado Springs, CO | 35.6 µg/m³ | 4.2 | Aug 21, 2018 | #5 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.
The evidence
News discovery (GDELT) 1
- Air quality advisory for wildfire smoke in effect for eastern Colorado The report cites a Colorado health advisory and states that smoke from U.S. wildfires blanketed eastern Colorado, with unhealthy fine-particle forecasts in the Denver metro. It corroborates wildfire-smoke influence in the episode window but does not quantify smoke-attributable PM2.5.
What remains uncertain
- The evidence resolves the broad cause but does not require a named fire, facility, or incident.
Status and provenance
Research preview: this record carries research-only status and its boundaries, cause, and name may change as evidence review completes. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula.