Fireworks EPA monitor flag
Daily PM2.5 peaked at 63.7 µg/m³ near Ogden across 1 covered metro home to 667,681 people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.6 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
Utah DEQ and the official monitor qualifier directly attribute the July 4 Ogden PM2.5 episode to fireworks emissions; the supplied reporting corroborates the post-fireworks spike.
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
U.S. EPA Air Quality System and the submitting air monitoring agency · Jul 4, 2012 official
EPA AQS carries an agency-submitted request-exclusion qualifier (RH, Fireworks.) on 1 PM2.5 sample in the candidate CBSA on 2012-07-04, identifying fireworks as affecting the sample. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
Utah Department of Environmental Quality · Oct 1, 2012 official
The Utah DEQ notice identifies the July 4, 2012 Ogden monitor value of 63.7 µg/m³ PM2.5 as due to firework-display emissions for exceptional-event review.
The Salt Lake Tribune · Jul 6, 2013 corroborates
Local reporting describes Utah Division of Air Quality monitoring of extreme PM2.5 spikes following July Fourth fireworks, corroborating the agency's documented fireworks effect in northern Utah.
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 request-exclusion qualifier (RH, Fireworks.) on 1 PM2.5 sample in the candidate CBSA on 2012-07-04, identifying fireworks as affecting the sample. A request-exclusion qualifier is an official submitting-agency…
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
Local reporting describes Utah Division of Air Quality monitoring of extreme PM2.5 spikes following July Fourth fireworks, corroborating the agency's documented fireworks effect in northern Utah.
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 “Fireworks” explanation; it does not assign the cause by itself.
Ogden-Clearfield, UT
Monitor comparison window 2012-07-01 to 2012-07-07 · PM2.5 target: Ogden
447% above nearby days
12% lower than surrounding days
252% higher than surrounding days
447% higher than surrounding days
252% higher than surrounding days
6% lower than surrounding days
About the same as surrounding days
68% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
12% 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.
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 |
|---|---|---|---|---|
| Ogden-Clearfield, UT | 63.7 µg/m³ | 2.9 | Jul 4, 2012 | #14 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 RH — Fireworks.
EPA AQS carries an agency-submitted request-exclusion qualifier (RH, Fireworks.) on 1 PM2.5 sample in the candidate CBSA on 2012-07-04, identifying fireworks as affecting the sample. A request-exclusion qualifier is an official submitting-agency causal claim, but this endpoint does not establish EPA concurrence.
Special Notice: Notice of Public Comment Period for the Fireworks Exceptional Events
The Utah DEQ notice identifies the July 4, 2012 Ogden monitor value of 63.7 µg/m³ PM2.5 as due to firework-display emissions for exceptional-event review.
Northern Utah pollution skyrockets with fireworks
Local reporting describes Utah Division of Air Quality monitoring of extreme PM2.5 spikes following July Fourth fireworks, corroborating the agency's documented fireworks effect in northern Utah.
EPA monitor flag EPA attached an exceptional-event qualifier to the affected samples. The agency flagged the measurement itself; no separate agency record describes the event.
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.