Evaluating the Use of Many Low-Cost Sensors for Monitoring NO 2 Gradients Presented by Timothy S. Dye, David L. Vaughn, Alison E. Ray, and Paul T. Roberts Sonoma Technology, Inc. Petaluma, CA Presented at the 2010 National Air Quality Conferences Raleigh, NC March 15-18,

2 Background Development of citizen monitoring –Efforts to miniaturize and personalize air quality monitoring –Currently in the research stage –Several pilot projects Many questions remain –Data quality –Representativeness –Usefulness (depends on application)

3 Example – CO and NO (UK) Group –University of Cambridge (England) Measurement –CO, NO, and NO 2 –Location Instrument –Small, low-cost sensors Source:

4 Example – CO and NO (UK) Source:

5 Example – CO and NO (UK) Source: CO NO

6 Example – Carbon Monoxide (San Francisco) Group: Intel Research Measurements –CO, O 3, NO 2 –Temperature and relative humidity –Location and light Instrument –Cell phone size –Solid-state sensors Tested on street sweepers in San Francisco Source: Allison Woodruff, Intel Research

7 Example – Carbon Monoxide (San Francisco) Existing routine CO monitoring sites in the SF Bay Area

8 Example – Carbon Monoxide (San Francisco) Source: Allison Woodruff, Intel Research CO monitoring locations using street sweepers in San Francisco

9 EPA NO 2 Sensor Feasibility Study Objective Evaluate the use of many small, low-cost NO 2 sensors to measure pollutant gradients near roadways Schedule: Now to August 2010 Components of study 1. Sensor characterization 2. Field study 3. Data analysis

10 EPA NO 2 Sensor Feasibility Study 1. Sensor characterization –Select sensor(s) –Perform simple evaluations in the laboratory Zero and upscale response Multi-concentration response (~4-5 concentration levels) Repeatability Response and recovery time Interferences (temperature, chemical, electrical) –Estimate precision and accuracy –Determine tradeoffs between cost and quality –Evaluate over a range of environmental conditions

11 EPA NO 2 Sensor Feasibility Study 1.Sensor characterization

12 EPA NO 2 Sensor Feasibility Study 1.Sensor characterization – our first test

13 EPA NO 2 Sensor Feasibility Study 2.Field study –Design sampling strategy with fixed and mobile sites –Install near “anchor” or standard NO 2 site –Collect surface meteorological measurements –Collect during a range of weather conditions Now New EPA Regulation Field Study Citizen State/Local monitor Fixed Study Site Path of Mobile Site

14 EPA NO 2 Sensor Feasibility Study 3. Data analysis –Analyze detailed NO 2 and meteorological data Time series analysis Spatial analysis Statistical analysis –Diagnose the spatial gradients in NO 2 near roads

15 Why Is This Important? Opportunity to –“Fill in the gaps” –Educate citizens –Change behavior –Engage and empower our communities Challenges –Data quality, representativeness, data use, formats, ownership, privacy, etc. –Increase coordination (for the government)

16 Where Will We Be in 3-5 Years? Thousands of citizens—perhaps tens of thousands—monitoring and reporting air quality

17 Where Will We Be in 3-5 Years? The “Citizen Environmental Monitoring Corps” is created to –Educate and certify citizens’ sensors –Empower citizens to make responsible air quality measurements “Open AIRNow” provides a framework for education, collaboration, and participation between citizens and government