Winter inversion
2019 early-March Denver metro inversion episode
Daily PM2.5 peaked at 58.6 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 ≈ 2.0 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 7.8 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.
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
State-agency meteorological attribution reported by Colorado Public Radio identifies a strong inversion that trapped local emissions in the Denver metro area; a National Park Service evaluation independently documents elevated PM2.5 during the same early-March period.
Sequence: Denver (Mar 6) → Colorado Springs (Mar 7)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Denver-Aurora-Lakewood, CO | 58.6 µg/m³ | 2.7 | Mar 6, 2019 | #8 of its top days |
| Colorado Springs, CO | 28.4 µg/m³ | 1.3 | Mar 7, 2019 | #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.
The evidence
Agency and publisher pages 2
- A Low-cost Air Quality Sensor for Measuring Particulate Matter A National Park Service evaluation using the state-operated Denver I-25 reference monitor documents elevated PM2.5 for approximately three days in the first week of March 2019, including a 77 µg/m³ reference-monitor concentration on March 7.
- Blame The Cold For Denver’s Smog This Week Colorado Public Radio reported a Colorado Air Pollution Control Division meteorologist’s assessment that a strong inversion trapped local emissions near the surface, producing high fine-particle levels in the Denver metro area.
What remains uncertain
- No named emissions source is supplied.
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.