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Air Quality Sensor Performance Evaluation Center
(AQ-SPEC)2015 PEMS CONFERENCE
March 27, 2015
Andrea Polidori, Ph.D. QA Manager; South Coast AQMD
• Permanent, large, fixed sites
• Address NAAQS
• Comply with CFR specs
• Sophisticated and highly accurate
• Expensive!
• Limited spatial resolution
Traditional Air Monitoring
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Community-Based Air Monitoring• Local concerns and issues
Resident complaintsPerceived health impactsRequests from other agencies, elected officials, etc.
• Often source-specific Special monitoring studiesDifferent approaches for different situations
• Non-regulatory
• Technologies deployedMonitoring trailersDeposition platesPortable monitorsGrab samples
• Enlist the help of residents
• Risk communication3
• Current efforts in South Coast Community based health studies Measurements conducted by
o University researcherso Local agencieso Consultantso Single Individuals (DIYers)o A combination of the above
• Technology used Portable monitors
o Non-FRM/FEM but quite reliable “Low-cost” air quality sensors
o Non-FRM/FEM; unknown performanceo Uncertain data quality
Monitoring By Community Groups / Others
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Low Cost Sensor TechnologySENSOR
PERFORMANCE• Only a few• Single pollutant measurements• Non-FRM/FEM
• Many (and more to come)•Single and multi-pollutant measurements
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• Air monitoring sensor information and data already available on the web
Low Cost Sensor Technology
http://elm.perkinelmer.com/map/
http://airqualityegg.comhttp://www.smartcitizen.me/
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Potential concerns• Rapid proliferation
• Data quality not on par with that of FRM and FEM instruments
• Potential “overload” in the amount of non-agency air monitoring data
• Technical Issues-Calibration, accuracy, interferences, time averaging, longevity, expertise of user
• Data interpretation-Which pollutant?-What levels?-False positives: unwarranted alarm-False negatives: false sense of security
• Confusion
Low Cost Sensor TechnologyOpportunities
• Low cost
• Relatively small size
• Ease of operation
• Broader community participation and awareness
• Wider spatial and temporal distribution-More refined control strategy -Early warning/community alert system
• Data available on web, smart-phones, etc.
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• European and US EPA efforts to gather information, encourage use, and engage the public but…
• …there is no State/Federal program to systematically evaluate sensor performance
Low Cost Sensor Technology
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Path Forward• Engagement, Education and Communication are essential Example: EPA STAR Grant "Air Pollution Monitoring for Communities”
• CAPCOA Conferences: Example: “My Air Quality: Using Sensors to Know What’s in Your Air”
o Northern California (BAAQMD): November 19, 2014o Southern California (SCAQMD): November 21, 2014
• What can SCAQMD do? Opportunity to provide leadership Utilize SCAQMD staff experience and expertise Establish AQ-SPEC (approved by Governing Board on July 2014)
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AQ-SPEC Overview• Main Goals & Objectives
Provide guidance & clarity for ever-evolving sensor technology & data interpretation Catalyze the successful evolution / use of sensor technology Minimize confusion
• Sensor Selection Criteria Potential near-tern use Real- or near-real time Criteria pollutants & air toxics Turnkey products first Price range:
o < ~$2,000 (purchase)o > ~$2,000 (lease/borrow)
AQMesh CairClip Shinyei
Dylos(prototype) DC1100 Pro SmartCitizens
AQ-SPEC OverviewFIELD TESTING
(Side-by-side comparison w/ FRMs)
vs
LAB TESTING(Controlled conditions)
RH = 30% T = 25C
Conc = 10 ppb
RESULTS(Categorize sensors based on performance)
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SCAQMD Website / Clearinghouse
AQ Officials
Community
Vendors
AQ-SPEC Overview
RESULTS
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AQ-SPEC Field Testing• Started on 09/12/2014
Sensor tested in triplicates Two month deployment Locations:
o Rubidoux station• Inland site• Fully instrumented
o I-710 station• Near-roadway site• Fully instrumented
AQ-SPEC Lab Testing
Dynamic dilution calibrator(CO, SO2, NOx, O3)
Zero Air
Particle generation system
Vent
Sensor #1
Sensor #2
Sensor #3
CO SO2 NOx VOC O3PM2.5 /
PM10 MassParticle Count
Particle Size Distribution
*Insulated
*Individual ports could be used instead
Design considerations: Dimensions, materialT and RH controlled: T (0-50 0C; +/- 5 0C); RH (5-95%; +/- 5%)
T and RH controlled
*Central data logger to collect
all data
Teflon fan
Teflon coated Stainless Steel
PM filter port needed?
AQ-SPEC Lab Testing ProtocolBased on EPA’s:• Sensor Evaluation Report • ORD Sensors/Applications Test Bed Challenge: Investigation of
Sensor/Application Response under Controlled Laboratory Conditions (by ALION; Air Casting test)
Test for:• (Conditioning)• Linearity of response (range)• Precision of measurement• Lower detectable limit• Concentration resolution• Response time• Interference equivalents• RH and T influences
Expected Results and Next Steps Provide the knowledge necessary to appropriately select, use,
and maintain sensors and to correctly interpret their data Promote a better and more responsible use of available
sensors Discover new and more effective ways to interact with local
communities Provide manufacturers with valuable feedback for improving
available sensors and for designing the next generation sensor technology
Create a “sensor library” to make “low-cost” sensors available to communities, schools, and individuals across California
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Field Testing – Preliminary Data
Dylos DC110• From 11/14/2014 to 01/09/2014 three Dylos particle counters (model DC1100)
were deployed in Rubidoux and run alongside two different FEM PM monitors
• Dylos (3 units tested): Optical particle counter (non-FEM)Measures 3 different size fractions
including PM(0.5-2.5) (used as an estimate of PM2.5)Cost: ~$300Time resolution: 1-min
• MetOne BAM (reference method): Beta-attenuation monitor (FEM) Measures PM2.5Cost: ~$20,000Time resolution: 1-hr
• GRIMM (reference method): Optical particle counter (FEM) Uses proprietary algorithms to
calculate total PM, PM2.5, and PM1 from particle number measurementsCost: ~$25,000 and upTime resolution: 1-min
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Field Testing Summary
5-min ave.R2>0.81
5-min ave.
1-hr ave.R2>0.63
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Shinyei PM2.5 Sensor• From 02/05/2015 to 03/03/2015, three Shinyei Technology PM2.5 Sensor Evaluation
Kits were deployed in Rubidoux and ran alongside two different FEM PM monitors
• PM Sensor Eval Kit (3 units tested): Particle sensors (non-FEM)Each unit measures: PM2.5 (ug/m3)
Unit cost: ~$1,000Time resolution: 1-minUnits IDs: SHN #1, SHN #2, SHN #3
• MetOne BAM (reference method): Beta-attenuation monitor (FEM) Measures PM2.5Cost: ~$20,000Time resolution: 1-hr
• GRIMM (reference method): Optical particle counter (FEM) Uses proprietary algorithms to
calculate total PM, PM2.5, and PM1 from particle number measurementsCost: ~$25,000 and upTime resolution: 1-min
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Field Testing Summary
1-hr ave.R2>0.925-min ave.
R2>0.84
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RTI MicroPEM• From 02/10/2015 to 03/09/2015, three RTI MicroPEM particle sensors were
deployed in Rubidoux and run alongside with two different FEM PM monitors
• RTI MicroPEM (3 units tested): Particulate Matter sensors (non-FEM)Each unit measures: PM2.5 (μg/m3)
Unit cost: ~$2,000Time resolution: 10secUnits IDs: 60N, 65N, 72N
• MetOne BAM (reference method): Beta-attenuation monitor (FEM) Measures PM2.5Cost: ~$20,000Time resolution: 1-hr
• GRIMM (reference method): Optical particle counter (FEM) Uses proprietary algorithms to
calculate total PM, PM2.5, and PM1 from particle number measurementsCost: ~$25,000 and upTime resolution: 1-min
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Field Testing Summary
1-hr ave.R2>0.81
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AeroQUAL S-500• From 02/10/2015 to 03/05/2015, three aeroQUAL Series 500 portable ozone
sensors were deployed in Rubidoux and run alongside an FRM O3 monitor
• aeroQUAL S-500 (3 units tested): Gaseous sensors (non-FRM)Each unit measures: Ozone (pphm)
Unit cost: ~$500Time resolution: 1-minUnits IDs: AQ #1, AQ #2, AQ #3
• SCAQMD FRM instruments: Ozone instrument; cost: ~$7,000
Time resolution: 1-minMeteorological station (wind speed,
wind direction temperature, relative humidity, and pressure); cost: ~$5,000Time resolution: 1-min
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Field Testing Summary
1-hr ave.R2>0.96
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Landtec AQMesh (1st gen)• From 09/27/2014 to 01/14/2015 four Landtec AQMesh gaseous monitors were
deployed in Rubidoux and run alongside FRM instruments for measuring CO, NO, NO2, SO2, and O3
• AQMesh (3 units tested): Electrochemical sensors (non-FEM)Each unit measures: CO, NO, NO2,
SO2, and O3Unit cost: ~$10,000Time resolution: 1- or 15-minUnits IDs: #83150, #495150 (until
11/12/2014), #574150 (starting on 12/08/2014), #90150
• SCAQMD FRM instruments: CO instrument; cost: ~$10,000
Time resolution: 1-minNOx instrument; cost: ~$11,000
Time resolution: 1-minSO2 instrument; cost: ~$13,000
Time resolution: 1-minO3 instrument; cost: ~$7,000
Time resolution; 1-min
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Field Testing Summary15-min ave.
0.72<R2<0.86
15-min ave.0.73<R2<0.86
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Field Testing Summary
15-min ave.
15-min ave.
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Field Testing Summary
15-min ave.
15-min ave.
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• Complete lack of correlation between AQMesh and FRM SO2 measurements
Field Testing Summary
15-min ave.
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SmartCitizen Kit• From 11/25/2014 to 01/28/2015, three Smart Citizen Kit (SCK) gaseous sensors
were deployed in Rubidoux and run alongside FRM instruments for measuring CO and NO2
• Smart Citizen Kit (3 units tested): Gaseous sensors (non-FEM)Each unit measures: CO (kOhm), NO2
(kOhm), Temperature (C) and Relative Humidity (%)Unit cost: ~$200Time resolution: 1-minUnits IDs: SCK#1, SCK #2, SCK #3
• SCAQMD FRM instruments: CO instrument; cost: ~$10,000
Time resolution: 1-minNOx instrument; cost: ~$11,000
Time resolution: 1-minMeteorological station (wind speed, wind
direction temperature, relative humidity, and pressure); cost: ~$5,000Time resolution: 1-min
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Field Testing Summary
5-min ave.0.48<R2<0.83
1-hr ave.R2>0.94
1-hr ave.R2>0.97
• Further analysis needed to validate the SCK NO2 data
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ConclusionsPM (optical) sensors:
• Minimal down time.• Low intra-model variability.• Strong correlation (R2) with two different FEM instruments.• A sensor “calibration” may be needed.• Potential sources of error:
Sensors cannot detect very small particles (e.g. <0.5 μm for Dylos). Bias in algorithms used to convert particle counts to particle mass.
Gaseous sensors:• Minimal down time. • Moderate intra-model variability.• CO; NO; O3 (when measured alone): moderate to strong R2 with FRM• O3 and/or NO2: low R2 with FRM (potential interference between O3 and NO2)• SO2: difficult to measure with current electrochemical sensors(?)
• Chamber testing is necessary to fully evaluate the performance of these sensors• All results are still preliminary
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