air quality sensor performance evaluation center (aq … · air quality sensor performance...

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




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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




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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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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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15-min ave.

15-min ave.

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15-min ave.

15-min ave.

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• Complete lack of correlation between AQMesh and FRM SO2 measurements


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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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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