Prescribed fire Likely
Daily PM2.5 peaked at 34.7 µg/m³ near Oklahoma City across 1 covered metro home to 1.5 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.2 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 1.7 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
NOAA satellite analysts documented a broad plume from numerous agricultural burns across northern Oklahoma on the exact event date.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
NOAA OSPO Hazard Mapping System · Apr 11, 2014 corroborates
NOAA observed a broad area of smoke from numerous agricultural burns stretching across the central and southern Plains, with clustered burns and moderate smoke in northern Oklahoma.
NOAA Satellite Services Division · Apr 11, 2014 hypothesis
NOAA satellite analysis documented smoke from Central Plains fires across central Kansas into the Oklahoma and Texas Panhandles and new smoke from fires in eastern/central Kansas and northeast Oklahoma; it does not establish smoke transport to Oklahoma City or attribute this PM2.5 event.
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
NOAA observed a broad area of smoke from numerous agricultural burns stretching across the central and southern Plains, with clustered burns and moderate smoke in northern Oklahoma.
View supporting source ↗Air-mass movement
NOAA observed a broad area of smoke from numerous agricultural burns stretching across the central and southern Plains, with clustered burns and moderate smoke in northern Oklahoma.
View transport source ↗Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 1.6 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 “Prescribed fire” explanation; it does not assign the cause by itself.
Oklahoma City, OK
Monitor comparison window 2014-04-08 to 2014-04-14 · PM2.5 target: OKC NORTH
188% above nearby days
27% lower than surrounding days
81% higher than surrounding days
188% higher than surrounding days
81% higher than surrounding days
89% higher than surrounding days
30% higher than surrounding days
Adjacent observations available
About the same as surrounding days
10% higher than surrounding days
About the same as surrounding days
27% lower 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 Oklahoma City
Peak-date arrivals · 2014-04-11
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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Oklahoma City, OK | 34.7 µg/m³ | 1.6 | Apr 11, 2014 | #22 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.
NOAA OSPO Hazard Mapping System
NOAA observed a broad area of smoke from numerous agricultural burns stretching across the central and southern Plains, with clustered burns and moderate smoke in northern Oklahoma.
A retained source supports the attributed cause for the stated place and dates.
Satellite detection does not quantify the surface PM2.5 share at Oklahoma City.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
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.