Caltech Team Launches Air Quality Monitor Network in Altadena to Monitor Dust, Ash Levels

In response to the Eaton fire that destroyed air quality monitoring equipment in Altadena, Caltech researchers have established a new PHOENIX network of particulate air quality sensors to provide residents and officials with real-time data on airborne dust levels as debris removal and rebuilding continue in the affected areas.

“With phase-2 debris removal underway, we wanted to give the community a source of independent air-quality measurements,” says Haroula Baliaka, a graduate student in environmental science and engineering at Caltech who has been working to install the PHOENIX sensors.

“At the same time,” Baliaka said, “the data can be used by agencies such as Federal Emergency Management Agency, the Environmental Protection Agency, and the Army Corps of Engineers to gauge how well dust-mitigation efforts are working.”

The network — whose name stands for Post-fire airborne Hazard Observation Environmental Network for Integrated Xposure-monitoring — consists of 19 sensors strategically placed across Altadena, including one at NASA’s Jet Propulsion Laboratory.

These solar-powered devices use cellular networks rather than Wi-Fi, allowing for quick installation and immediate data transmission.

Each sensor measures particulate matter in three size categories: less than 1 micrometer (PM1.0), less than 2.5 micrometers (PM2.5), and larger particles up to 10 micrometers (PM10). Data from the PHOENIX sensors can be viewed online and are updated every five minutes.

Paul Wennberg, Caltech’s R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering who spearheaded the project, explains why tracking larger particles is especially important: “That means these larger particles are much more indicative of local dust events. Since one of our goals was to be able to isolate from the general aerosol pollution of Los Angeles things that were more related to the fire debris, we needed sensors capable of good PM10 measurements.”

The sensors have been placed approximately one kilometer apart to monitor dust movement effectively.

“If you have a dust source during the day and if it’s made out of the ash and the dust from these houses, it will get transported some distance,” says Wennberg. “So we’re trying to place our sensors roughly a kilometer apart in every direction to be able to isolate and figure out where the dust is coming from.”

Before the fire, PurpleAir sensors monitored air quality throughout Altadena, but these devices were either burned or left without Wi-Fi and utility power needed to keep them running after the blaze. “We had lost this important data for everybody in the community,” Wennberg says. “All those PurpleAir sensors had just evaporated.”

At the same time, data from the ASCENT (Atmospheric Science and Chemistry mEasurement NeTwork) site in Pico Rivera was showing heightened levels of toxins such as lead and chlorine in the small particulate matter in air coming downwind from the fire.

Multiple schools host the new sensors, including EF Academy, Odyssey Charter School, Saint Mark’s School, and Saint Elizabeth Parish School. Additional units will soon be installed at Pasadena Unified School District sites, and parents at Crestview Preparatory School in La Cañada Flintridge raised funds to purchase their own sensor.

While the PHOENIX website currently shows only raw data from the various sensors, the team plans to continue incorporating additional features to the site that will illustrate general air quality across Altadena and identify dust events. The team also aims to make the data as accessible as possible and to use machine learning and predictive models to gain additional insights.

The rapid deployment was made possible through funding from members of the GPS Chair’s Advisory Council, supporters of Caltech’s Division of Geological and Planetary Sciences, and the Resnick Sustainability Institute. Additional sensors were loaned from JPL, Georgia Institute of Technology, and the ASCENT network, while the City of Pasadena is purchasing a sensor for its Public Health Department building. QuantAQ donated a year of Caltech’s two-year service contract for operating the devices.

“It all came together so quickly,” Wennberg says. “This seemed like something in our wheelhouse that could really help the community. But it was really Haroula who said, ‘We have to do this.'”