Residential combustion Agency determination

2007-01-15 residential combustion episode affecting Seattle-Tacoma-Bellevue, WA

January 15, 2007

Daily PM2.5 peaked at 71.6 µg/m³ near Seattle across 1 covered metro home to 4.1 million people.

Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.9 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

The basis for “Residential combustion”

Qualified frozen causal evidence supports residential combustion as the broad root cause.

Agency determination A government body issued a record naming this cause for this event: an NWS air-quality alert, a NOAA Storm Events record, or a state or local official archive.

Puget Sound Clean Air Agency official

Burn Ban Status As Of: 1/15/2007

The official historical status records a Stage 1 air-quality burn ban in King, Pierce, and Snohomish counties on January 15, 2007, effective January 13. The agency's linked burn-ban explanation states that these winter restrictions respond to degraded fine-particle air quality when stagnant conditions allow residential wood smoke to accumulate. This supports residential combustion as a cause affecting the Seattle metro episode, but does not quantify its share of the observed PM2.5.

See every retained source and limitation ↓

Evidence path

From source to city

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.

Open the evidence ledger ↓

1

Source or mechanism

Residential combustion

The official historical status records a Stage 1 air-quality burn ban in King, Pierce, and Snohomish counties on January 15, 2007, effective January 13. The agency's linked burn-ban explanation states that these winter restrictions respond to…
View supporting source ↗
Documented
2

Air-mass movement

The transport path has not been reconstructed

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.

Research gap
3

Local response

71.6 µg/m³ near Seattle

EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 3.3 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓
Documented

Event autopsy

What the instruments saw

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.

Observed context · not attribution

Seattle-Tacoma-Bellevue, WA

Monitor comparison window 2007-01-12 to 2007-01-18 · PM2.5 target: DARRINGTON - FIR ST (Darrington High School)

4 pollutant signals

Fine-particle pulse 33.5 µg/m³

14% above nearby days

Air movement 2.50 kt

40% higher than surrounding days

PM10 40 µg/m³

54% higher than surrounding days

Pollution fingerprint

Metro-wide median of reporting monitors

PM2.5 33.5 µg/m³

14% higher than surrounding days

Before32.7 µg/m³ Event33.5 µg/m³ After14.9 µg/m³

PM10 40 µg/m³

54% higher than surrounding days

Before28 µg/m³ Event40 µg/m³ After18 µg/m³

Carbon monoxide 1.37 ppm

38% higher than surrounding days

Before0.996 ppm Event1.37 ppm After0.908 ppm

Ozone 0.014 ppm

6% lower than surrounding days

Before0.018 ppm Event0.014 ppm After0.014 ppm

Atmospheric conditions

Nearby EPA weather observations

Humidity 94.4 %

About the same as surrounding days

Temperature 30.5 °F

About the same as surrounding days

Wind 2.50 kt

40% higher 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.

Measured daily PM2.5 at EPA monitors, as cigarette-equivalents

EPA monitors sit in metro areas, so the colour clusters there. Land between and beyond them is unmeasured, not clean: this map shows where IAQng has readings, not the extent of the smoke.

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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

Camera views near

Browse the camera map →

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.

Affected metros

Metro	Peak PM2.5	Cigarettes, whole event	Peak day	All-time standing
Seattle-Tacoma-Bellevue, WA	71.6 µg/m³	3.3	Jan 15, 2007	#18 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

What supports this account

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.

state-local-official-archive-discovery-v1 1

Burn Ban Status As Of: 1/15/2007

Puget Sound Clean Air Agency official government

The official historical status records a Stage 1 air-quality burn ban in King, Pierce, and Snohomish counties on January 15, 2007, effective January 13. The agency's linked burn-ban explanation states that these winter restrictions respond to degraded fine-particle air quality when stagnant conditions allow residential wood smoke to accumulate. This supports residential combustion as a cause affecting the Seattle metro episode, but does not quantify its share of the observed PM2.5.

Status and provenance