Residential combustion Possible
Daily PM2.5 peaked at 62.7 µg/m³ near Phoenix across 1 covered metro home to 5.2 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.3 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 12 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
An exact-date PM2.5 advisory and an official same-place holiday pattern support residential wood burning trapped by winter inversion as a reasonable hypothesis.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
Maricopa Association of Governments official
MAG states that Phoenix's worst winter PM2.5 exceedances generally occur on Christmas and New Year holidays when inversions trap pollution from residential wood burning and consumer fireworks; Christmas Eve is part of the named pattern.
KJZZ · Dec 23, 2022 corroborates
Contemporaneous reporting states that ADEQ issued a PM2.5 High Pollution Advisory through Christmas Sunday for metro Phoenix.
KJZZ · Dec 23, 2022 hypothesis
KJZZ reported an ADEQ PM2.5 High Pollution Advisory covering Christmas Eve and Christmas Day, including restrictions on residential wood burning.
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
MAG states that Phoenix's worst winter PM2.5 exceedances generally occur on Christmas and New Year holidays when inversions trap pollution from residential wood burning and consumer fireworks; Christmas Eve is part of the named pattern.
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
Contemporaneous reporting states that ADEQ issued a PM2.5 High Pollution Advisory through Christmas Sunday for metro Phoenix.
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 “Residential combustion” explanation; it does not assign the cause by itself.
Phoenix-Mesa-Scottsdale, AZ
Monitor comparison window 2022-12-21 to 2022-12-27 · PM2.5 target: SOUTH PHOENIX
34% above nearby days
6% lower than surrounding days
About the same as surrounding days
34% higher than surrounding days
About the same as surrounding days
21% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
28% higher than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
6% 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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Phoenix-Mesa-Scottsdale, AZ | 62.7 µg/m³ | 2.9 | Dec 24, 2022 | #25 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.
Maricopa Association of Governments
MAG states that Phoenix's worst winter PM2.5 exceedances generally occur on Christmas and New Year holidays when inversions trap pollution from residential wood burning and consumer fireworks; Christmas Eve is part of the named pattern.
An official source supports the attributed cause for the stated place and dates.
The page describes a recurring local pattern rather than a retrospective determination for December 24, 2022.
KJZZ
KJZZ reported an ADEQ PM2.5 High Pollution Advisory covering Christmas Eve and Christmas Day, including restrictions on residential wood burning.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
A prospective advisory confirms the expected episode but is not itself retrospective attribution.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
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.