Cheap Personal Air Monitoring Devices Show Promise

By Michael J. Bologna

March 16 — Initial results from an analysis of inexpensive personal air quality sensors suggest a high level of reliability and strong correlation in side-by-side field tests with more expensive, federally accepted air monitoring devices, a senior compliance officer of the South Coast Air Quality Management District (SCAQMD) said March 16.

Mohsen Nazemi, deputy executive officer in SCAQMD’s Office of Engineering and Compliance, said the district's initial tests of ambient concentrations of gaseous and particle pollutants using personal air quality sensors suggest great promise for the emerging technology. Nazemi cautioned, however, that SCAQMD's assessments are “preliminary,” adding that his Los Angeles area air management district would like to pursue a series of pilot tests of the devices before reaching hard conclusions.

“There is tremendous potential for using these in various arenas. There are multiple applications—spacial, temporal. You can use it for fence line [monitoring]. You can also use it in regulatory, academia and citizen science contexts,” Nazemi said during a presentation at the National Association of Clean Air Agencies’ “Communicating Air Quality” conference in Chicago.

He added, “the only question is, how reliable and accurate are these sensors?”

The evaluations Nazemi discussed were performed under SCAQMD's Air Quality Sensor Performance Evaluation Center (AQ-SPEC) program, the first program in the nation to scientifically evaluate the reliability, precision and quality of personal air quality sensors. The Environmental Protection Agency and state air quality agencies are expected to consider the results from the AQ-SPEC program if they integrate personal air quality sensors into their regulatory frameworks.

While the devices are expected to generate critical information about public exposure to air pollution, some industry groups and regulators have expressed concerns about the quality of the data generated. Many believe data quality gaps must be mastered before the devices are appropriate for regulatory decision making .

Field, Lab Testing

Nazemi said AQ-SPEC was launched in July 2014 with a $600,000 grant to evaluate the performance of commercially available air quality sensors in both field and laboratory environments. He said the project also hopes to influence the evolution and development of sensor technology.

Under the AQ-SPEC testing protocol, Nazemi said more than a dozen brands of sensors were operated side-by-side with Federal Reference Methods (FRM), Federal Equivalent Methods (FEM) air monitoring equipment. The project focused on various manufacturers of metal-oxide sensors, electrochemical sensors and optical sensors. The testing was conducted at the SCAQMD Rubidoux stationary ambient air monitoring station or at one of the district's roadway sites. Three of each brand's sensors were deployed in the field for two months and compared to FRM/FEM instruments.

Nazemi presented findings and approximate costs for four common sensors:

  • AirBeam Particulate Matter sensor ($200). The three AirBeam sensors were “reliable,” but AQ-SPEC found “substantial intra-model variability.” Nazemi said the results suggest users may need to continually calibrate the devices.
  • Dylos optical particle counter ($300). The three Dylos units “performed well,” and showed no down time, minimal intra-model variability and good correlation with FEM instruments.
  • The aeroQUAL S500 gaseous sensor ($500). The three aeroQUAL sensors “performed very well,” demonstrating minimal down time, low intra-model variability, and “very good correlation” with more expensive FRM instruments.
  • Smart Citizen Kit gaseous sensor ($200). The carbon monoxide (CO) data measured correlated well with corresponding FRM data. The three units did not provide reliable nitrogen dioxide (NO2) concentrations. Smart Citizen is currently developing an improved version of its sensor.

    Revolutionizing Compliance

    Joel Creswell, a science policy fellow in the EPA’s Office of Research and Development, said the EPA is closely watching AQ-SPEC's progress within the framework of its Advanced Monitoring project. Recognizing that new technologies could quickly revolutionize environmental compliance, he said the project would guide the EPA toward new protocols for efficiently monitoring air quality.

    Cresswell noted, however, that testing projects such as AQ-SPEC still need to demonstrate the reliability of commonly available sensors prior to any changes in compliance protocols.

    “The data quality of a lot of instruments is unknown,” Creswell said during the same NACAA panel discussion. “A low quality instrument creates two problems: 1) it could show a big problem where there isn’t and 2) it could miss a big problem where there is one.”

    To contact the reporter on this story: Michael J. Bologna in Chicago at

    To contact the editor responsible for this story: Larry Pearl at