Use and evaluation of low cost sensors for the monitoring of NO 2 and O 3 in ambient air

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1 Use and evaluation of low cost sensors for the monitoring of NO 2 and O 3 in ambient air Michel Gerboles, Pascual Ballesta and Laurent Spinelle European Commission, Joint Research Centre, I Ispra (VA)

2 Fixed/indicative measurements: definition fixed measurements measurements taken at fixed sites, to determine the levels in accordance with the relevant Data Quality Objectives (DQO); indicative measurements measurements which meet DQOs that are less strict than those required for fixed measurements; They are use to monitor Limit Values during an Averaging Time (for ozone 60 ppb mean of 8 hourly values) European DIRECTIVE 2008/50/EC on ambient air quality and cleaner air for Europe, art. 2 2

3 Data Quality Objectives (DQO) of the European Air Quality Directive O 3 SO 2, NO 2 /NO/ NOx, CO Benzene DQO: Uncertainty for indicative measurements DQO: Uncertainty for reference measurements 30 % 25 % 30 % 15 % 15 % 25 % 3

4 Indicative methods: what for? Fixed measurements are mandatory in zones and agglomerations where the upper assessment thresholds are exceeded, otherwise indicative methods can be used. The use of indicative measurements allows for reduction of 50 % of the required minimum number of fixed sampling points. European DIRECTIVE 2008/50/EC on ambient air quality and cleaner air for Europe, art. 6 4

5 Field of application: limit value, averaging time and Data Quality Objective Type of station/zone: e.g. O 3 rural background air composition (test gas and interferents) 1 Response time 2 Pre-calibration 3.1 Short term drift 3.2 Long term drift Averaging time Calibration function to eliminate bias at central point Max time between tests, limit of detection, repeatability Correction of drift - periodicity of re-calibration 4 Interference testing: gas compounds, meteo (T, RH,P, wind...), hysteresis... laboratory design of experiments (significant parameters ) No Lab. Model equation lab. uncertainty U(lab) 5.1 Lab. experiments U(lab) < DQO? Yes 5.2 Field tests - U(field) No Lab. Model correct in field? 6 Additional information: cold, warm and hot start... No U(Field) <U(lab) Yes Yes The sensor is accepted as an indicative method No U(field)<DQO 5

6 Tests Comments on test gas level or interferent Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 80 % of FS, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 24 September , 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) 5-1 Lab experiments (model) 5-2 Field experiments 6 Cold start, warm start, hot start 0, LV, AT for each significant parameter: temperature and humidity (3 levels) and interference (2 levels) At an automatic station equipped with reference method of measurements -10 C, mean, mean -10 C, if found significant -20%, mean, mean + 20 %, if found significant At LV 6

7 On-site measurements 24 September

8 On-site measurements Inlet sampling line Sensors Meteorological mast

9 Manufacturer Model Type OUnitec 3 Sensors s.r.l IT O 3 Sens 3000 Resistive Ingenieros Assessores SP NanoENvi mote and MicroSAD datalogger, with Oz-47 sensor Resistive αsense - UK O 3 sensors (O3B4) 4 electrodes Citytech G Sensoric 4-20 ma Transmitter Board with O3E1 sensor 3 electrodes Citytech G Sensoric 4-20 ma Transmitter Board with O3E1F sensor 3 electrodes CairPol F CairClip O3 3 electrodes e2v CH MiCS-2610 sensor and OMC2 datalogger, Resistive e2v CH MiCS Oz-47 sensor and OMC3 datalogger Resistive IMN2P FR Prototype WO3 sensor with MICS-EK1 Sensor Evaluation Kit Resistive FIS - J SP-61 sensor and evaluation test board Resistive

10 NO 2 Sensors Manufacturer Unitec s.r.l IT Sens 3000 Ingenieros Assessores SP αsense UK Citytech G Model NanoENvi mote and MicroSAD datalogger, unidentified sensor probably e2v-mics sensor NO 2 sensors (B4 series) Sensoric 4-20 ma Transmitter Board with 3E50 sensor Citytech UK A3OZ EnviroceL (NO2 and O3) MIKES FI InRim IT Prototype graphene sensors Prototype graphene sensors

11 1 - Response time Rise Time (n=3) Fall Time (n=3) Average Time Response time per type Chamber UV analyser (substracted) Unitec, Sens3000 (n =2) 47 ' 75 ' 61 ' e2v, MICS-2610 (n =2) 1 ' 12 ' 6 ' FIS, SP-61(n =2) 57 ' 54 ' 56 ' Ingenieros Assessores, NanoEnvi (n =1) 8 ' 14 ' 11 ' 31 ' e2v, OMC3 (n=2) e2v, OMC2 (n=2) e2v, MICS_Oz47 (n =7) 19' 27' 23' IMN2P, WO3 (n =2) 8' 16' 12' 12 ' Sensoric, O3E1F + Test Panel (n =1) 1' 2' 2' Sensoric, O3E mA Board (n =2) 4 ' 5 ' 4 ' αsense B4 (n =2) 1 ' 2 ' 2 ' 3 ' CairclipO3NO2 (n=1) 3 ' 3 ' 3 ' Sensors Average response Time 15' 21 ' 18 '

12 Tests Comments on test gas level or interferent Temperature, ºC Rela6ve humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 80 % of FS, 3 repetitions every averaging time Short term drift Long term drift 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) 0, LV, AT for each significant parameter: temperature -10 C, mean, mean -20%, mean, mean Lab experiments and humidity (3 levels) and interference (2 levels) -10 C, if found significant %, if found significant At an automatic station equipped with reference 5-2 Field experiments method of measurements 3 months Cold start, warm 6 At LV start, hot start

13 2 - Pre-calibration

14 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 3-2 Short term drift 3-3 Long term drift 0 and 80 % of FS, 3 repetitions every averaging time 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) Lab experiments 0, LV, AT for each significant parameter: temperature -10 C, mean, mean -20%, mean, mean (model) and humidity (3 levels) and interference (2 levels) -10 C, if found significant %, if found significant At an automatic station equipped with reference 5-2 Field experiments method of measurements Cold start, warm 6 At LV

15 3.1 - Repeatability (hourly values) O3 ppb CairClipO3 ppb (n=9) 0 NA (n=13) ± 0.5

16 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 90 % of LV, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 0, 50 % and 80 % of FS, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) Lab experiments 0, LV, AT for each significant parameter: temperature -10 C, mean, mean -20%, mean, mean (model) and humidity (3 levels) and interference (2 levels) -10 C, if found significant %, if found significant At an automatic station equipped with reference 5-2 Field experiments method of measurements Cold start, warm 6 At LV start, hot start

17 3.2 - Short term stability 1 day drift at 0, 60 and 90 ppb Diff. at 0 ppb (n~19) Diff. at 60 ppb % (n~8) Diff. at 90 ppb (n~6) Res 1 (n =2) % % Res 2 (n =2) Res 3 (n =2) % % Res 4 (n =2) % % Res 5 (n=2) Res 6 (n=2) Res 7 (n =1) % % Res 8 (n =2) % % Chem 1 (n =1) % % Chem 2 (n =2) Malfunc@on Malfunc@on Malfunc@on Chem 3 (n = 2) % % Chem 4 (n=1) 3.4 ± ± ± 0.7

18 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 90 % of LV, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of FS, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) Lab experiments 0, LV, AT for each significant parameter: temperature -10 C, mean, mean -20%, mean, mean (model) and humidity (3 levels) and interference (2 levels) -10 C, if found significant %, if found significant At an automatic station equipped with reference 5-2 Field experiments method of measurements Cold start, warm 6 At LV start, hot start

19 a) Long term stability, 150 days Scatterplot of V011_21 (V) Ozone, UV Photometry = 0 nmol/mol: y = E-5*x; r 2 = Ozone, UV Photometry = 60 nmol/mol: y = E-5*x; r 2 = Ozone, UV Photometry = 90 nmol/mol: y = E-6*x; r 2 = V011_ Number of Day

20 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 90 % of LV, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of FS, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) Lab experiments 0, LV, AT for each significant parameter: temperature -10 C, mean, mean -20%, mean, mean (model) and humidity (3 levels) and interference (2 levels) -10 C, if found significant %, if found significant At an automatic station equipped with reference 5-2 Field experiments method of measurements Cold start, warm 6 At LV

21 4.2 - Gaseous interference O 3 sensors Sensors/ NO 2 NO CO CO 2 NH 3 Interference, ppb Purified air ± 85 O3, ppb RH (%) T (ºC) 60 % 22 ºC 60 % 22 ºC 60 % 22 ºC 60 % 22 ºC 60 % 22 ºC Res 1 (n =2) 14.1 % % 9.8 % -6.2 % 6.0 % Res 2 (n =2) -3.3 % % -0.1 % -0.3 % Res 3 (n =2) 14.5 % -10 % 13.4 % 5.0 % 18 % Res 4 (n =2) 12.6 % -1.6 % -8.9 % 1.0 % 3.5 % Res 5 (n=2) Res 6 (n=2) Res 7 (n =1) Res 8 (n =2) 1.2 % -0.8 % 0.1 % -0.2 % -1.9 % Chem 1 (n =1) 89.3 % 1.3 % -0.9 % 0.2 % 1.2 % Chem 2 (n =2) Chem 3 (n = 2) 33.7 % -7.7 % -1.2 % -0.4 % 0.1 % Chem 4 (n=1) % -1.5 % -2.4 % 0.4 % 2.3 %

22 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 80 % of FS, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean +10 C by steps of 5 C 4-4 Humidity At LV From mean-20% to mean +20% by steps of 10% 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) Lab experiments 0, LV, AT for each significant parameter: temperature 5-1 (model) and humidity (3 levels) and interference (2 levels) At an automatic station equipped with reference 5-2 Field experiments -10 C, mean, mean -10 C, if found significant -20%, mean, mean + 20 %, if found significant

23 4.3 Temperature

24 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 80 % of FS, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV From mean-20% to mean +20% by steps of 10% 4-5 Hysteresis Increasing-decreasing-increasing cycles of the levels used for pre-calibration 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) Lab experiments 0, LV, AT for each significant parameter: temperature 5-1 (model) and humidity (3 levels) and interference (2 levels) At an automatic station equipped with reference 5-2 Field experiments method of measurements -10 C, mean, mean -10 C, if found significant -20%, mean, mean + 20 %, if found significant

25 4.5 - Hysteresis

26 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 80 % of FS, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) 5-1 Lab experiments 5-2 Field experiments Cold start, warm At least 3 gas test levels for each significant parameter: temp. and humidity (3 levels) and interference (2 levels) At an automatic station equipped with reference method of measurements -10 C, mean, mean -20%, mean, mean C, if found significant 20 %, if found significant

27 5.1 - Experimental design O 3, ppb NO 2, ppb Temp. Rel. Hum. Total levels 2 levels 3 levels 3 levels 108 trials

28 5.1 - Experimental design

29 Tests Comments on test gas level or interferents Temperature, ºC Relative humidity, % 1 Response Time 0 to 80 % of full scale (FS) - 80% of FS to 0 2 Pre-calibration At least 3 levels of test gas (limit value LV) 3-1 Repeatability 0 and 80 % of FS, 3 repetitions every averaging time 3-2 Short term drift 3-3 Long term drift 0, 50 % and 80 % of LV, 3 repetitions per day for 3 consecutive days 0, 50 % and 80 % of LV, repeated every 2 weeks during 3 months 4-1 Air matrix Zero air, laboratory air and ambient air at 0 and LV 4-2 Gas interference Test selected interferences at 0 and mean level in ambient air, test gas at 0 and LV of test gas 4-3 Temperature At LV From mean-10 C to mean+10 C by steps of 5 C 4-4 Humidity At LV 4-5 Hysteresis Increasing-decreasing-increasing cycles of the test gas levels used for pre-calibration From mean-20% to mean +20% by steps of 10% 4-6 Pressure overpressure 10 mbar and under pressure 5 mbar 4-7 Power supply effect At LV test under 210, 220 and 230 V 4-8 Wind velocity from 1 to 5 m/s (needed?) Lab experiments (model) Field experiments Cold start, warm start, hot start 0, LV, AT for each significant parameter: temperature and humidity (3 levels) and interference (2 levels) At an automatic station equipped with reference method of measurements -10 C, mean, mean -10 C, if found significant -20%, mean, mean + 20 %, if found significant At LV

30 5.2 Field tests, hourly values

31 5.2 Uncertainty and DQO Ø U = 2 (s² lof + s² bias s r,uv ² ) < DQO = 30 % U, ppb, Hourly values, validation datas 60 ppb 26 % 90 ppb 19 % 120 ppb 17 %

Protocol of evaluation and calibration of low-cost gas sensors for the monitoring of air pollution. L. Spinelle, M. Aleixandre and M.

Protocol of evaluation and calibration of low-cost gas sensors for the monitoring of air pollution L. Spinelle, M. Aleixandre and M. Gerboles 0 1 3 Report EUR 611 EN European Commission Joint Research