Until relatively recently, air quality monitoring has only been performed by air quality regulatory agencies using expensive, sophisticated monitoring devices subject to strict siting and quality-assurance requirements; data are compared against national and state health-based regional air quality standards. Within the past decade, low-cost ($100-$2,500) air sensors have become commercially available in a wide variety of designs and capabilities.
Low-cost sensors vary widely in performance and reliability, and measure very localized, neighborhood-level air quality in short periods of time, meaning data do not always align with the regional air quality health standards. There are efforts underway at the state and national levels to assess the performance of the low-cost air sensors and to develop ways to look at the short-term localized data in terms of health effects.
PurpleAir Sensors and Community Partners
One of the more popular low-cost air sensors that have performed well, as evaluated by SCAQMD AQ-SPEC, is made by the company PurpleAir. These sensors can detect fine and ultra-fine particulates (PM10 and PM2.5, respectively). Data is shared through the PurpleAir map and the AirNow Fire & Smoke (opens in a new tab) map. The data is uploaded in real time and available for anyone to see. The AirNow map applies a correction factor to the data, improving reading accuracy for wildfire smoke conditions.
Low-cost air sensors, such as PurpleAir, provide informative data, and are a popular tool for community members to understand localized, neighborhood-specific air quality conditions, providing additional information to the regional conditions monitored by the District’s more sophisticated air quality monitoring network. However, low-cost air sensors do not meet federal, state, or local regulatory requirements for air quality monitoring, air quality warnings, or enforcement. Therefore, the District cannot use sensor data for any enforcement or regulatory purposes.
At the December 2018 meeting, the District’s Board of Directors approved the District to enter into agreements with community partners interested in installing District-owned PurpleAir sensors at select locations throughout the county. Since then, the District has installed over 50 sensors at K-12 schools and organizations countywide. The District provides these sensors as a tool for communities to better understand localized air quality conditions. Please see here (opens in a new tab) and here for more information.
New Low-Cost Sensor Installation Opportunities – 2025
In June 2025, the District’s Board of Directors approved the District to administer a PurpleAir air quality sensor deployment program with $40,000 in funding from the California Air Pollution Officer’s Association (CAPCOA). This will allow the District to install upwards of 100 air sensors throughout the county. Interested community partners should view the Letter of Expectations for partners and contact [email protected] for questions and inquires related to low-cost air sensors and their use in Santa Barbara County. Interested partners can also fill submit information via the online form. See September 10, 2025 news release for more information.
Study in New Cuyama (2016)
In 2016, the District worked with Sonoma Technology, Inc. to study low-cost portable air sensors. Study participants collocated low-cost sensors and reference method sensors at Cuyama Valley High School to evaluate how the sensors performed during high wind events. See Final Report (opens in a new tab) of this study, and the photo above of District Monitoring Specialists setting up the monitoring station at Cuyama Valley High School.
Additional Resources
Powerpoint Presentation: ARB’s Perspective on Next Generation Air Monitoring Technology (opens in a new tab)
EPA’s Air Sensor Toolbox for Citizen Scientists (opens in a new tab)
EPA’s Paper on Regulatory Considerations of Lower Cost Air Pollution Sensor Data Performance (opens in a new tab)
EPA’s What Do My Sensor Readings Mean? (opens in a new tab)
The South Coast Air Quality Management District (SCAQMD (opens in a new tab)) has developed an Air Quality Performance Evaluation Center (AQ-SPEC (opens in a new tab)) to evaluate the viability of low-cost air sensors. The evaluation consists of both field and laboratory studies of the sensors. For more details, see SCAQMD’s paper on Laboratory Evaluation of Low-Cost Sensors (opens in a new tab). Visit the AQ-SPEC webpage (opens in a new tab) for additional information about the program and results.