About SJVAir

SJVAir is a network of low-cost air quality monitors providing real-time PM2.5 data to disadvantaged communities across the San Joaquin Valley. SJVAir is operated by a collaborative of non-profit organizations from Bakersfield to Stockton.

The Central California Asthma Collaborative works across the entire San Joaquin Valley to reduce the burden of asthma and related conditions through education, intervention, policy analysis and advocacy by improving care and reducing air pollution.

Root Access is a community (hacker/maker/work)space that supports Fresno's technology and maker scene. They provide the community with access to tools and equipment and a space to share knowledge and experiment in a creative and collaborative environment.

Central California Environmental Justice Network's mission is to empower our communities and secure our children's future by eliminating negative environmental impacts in low income and communities of color in the Central Valley.

Valley Improvement Projects' mission is to improve the quality of life of under-represented and marginalized residents of Stanislaus County and the Central Valley by advocating for social and environmental justice.

For over 70 years, Catholic Charities of the Diocese of Stockton has provided social services to people in San Joaquin, Stanislaus, Calaveras, Tuolumne, Alpine, and Mono counties. We believe in the inherent dignity of each person and create services that support families and enhance the quality of life for all members of the community regardless of race, age, or religion. Today, Catholic Charities administers direct social services and advocacy through a variety of programs for the most vulnerable and under represented citizens of our communities.

Little Manila Rising is a social justice organization whose mission is to develop equitable solutions to create a more inclusive and healthy community for all San Joaquin County residents.

Air Monitor Testing & Calibration

Root Access provided the space for testing and calibration of SJVAir's PurpleAir monitors before they were put into the field for data collection.

SJVAir PurpleAir monitors are assessed for inter-device variability at Root Access prior to being deployed in the field. Particle count data from deployed PurpleAir monitors is regressed on collocated regulatory monitor data to generate correction equations (calibrations).

Testing: two batches of PurpleAir monitors were operated continuously on the roof at Root Access. During the first test period (12/10/2019 – 1/9/2020), 30 monitors were run for 30 days with an average hourly concentration of 36 ug/m3 and a range of 1-180 ug/m3. During the second test period (1/21/2020 – 2/20/2020), another 30 monitors were run for 31 days with an average hourly concentration of 35 ug/m3 and a range of 1-85 ug/m3. The average correlation (R2) for all 60 monitors was 0.96. Only one monitor had an R2 < 0.90 (this monitor was returned to the manufacturer).

Calibration: in the example shown here, hourly PM2.5 mass values from regulatory monitors in Visalia (Church St) and Fresno (Garland Ave) were regressed on particle counts (0.3-1.0 um/dl and 1.0-2.5 um/dl) from collocated PurpleAir monitors at each site from Aug 20-22, 2020. The R2 for these multivariate regressions was 0.992 and 0.990, respectively. Correlation coefficients for Visalia and Fresno were applied separately to particle count data from the PurpleAir monitor in Visalia to generate "locally" (Visalia coefficients) and "regionally" (Fresno coefficients) calibrated values. Also shown are the uncalibrated and EPA calibrated (AirNow) values for the Visalia PurpleAir monitor.

We believe in Open.

We subscribe to the ideals of Open Source software, hardware, and data, and believe that these things should be freely available to the public for the benefit of everyone. We're making a commitment that the technology that powers SJVAir will be published on Github and our API will be documented and freely available for anyone to use. More information will be available soon.

github.com/sjvair sjvair.com/api


SJVAir wouldn't be possible without the thousands of people who have generously given their time to build and maintain these and other Open Source projects.