European Network on New Sensing Technologies for Air Pollution Control and Environmental Sustainability - EuNetAir COST Action TD1105 WGs and MC Meeting at ISTANBUL, 3-5 December 2014 Action Start date: 01/07/2012 - Action End date: 30/06/2016 Year 3: 1 July 2014 - 30 June 2015 (Ongoing Action) GAS AND PARTICULATE MONITORS: ADVANCES AND SETBACKS John Saffell WG 4.3 Alphasense Ltd. COST is supported by the EU Framework Programme UK ESF provides the COST Office through a European Commission contract Air Quality sensors: problems and progress Inorganic gases • Separating NO2 and O3 • improving ppb linearity • improving humidity response Particulates • PM2.5, PM10, PM1 VOCs • PIDs: better sensitivity, longer lamp life • Metal oxides: how low can we go? 2 Good air quality sensor: Sensitivity Selectivity Stability ( T, humidity, time) and…..low cost! Inorganic gases: NO2 and O3 (1/2) The problem Both gases are strong oxidants, causing lung oxidative stress WO3 metal oxide is used to measure O3, but thermal decomposition is the challenge Graphite electrochemical cells measure both NO2 and O3, so we must scrub O3 in one sensor, while measuring both gases in the second sensor to measure both NO2 and O3 SnO2 metal oxides measure both NO and NO2 4 Inorganic gases: avoiding NO, while scrubbing O3 (2/2) The solution OX-B421 and NO2-B42F 2ppm NO 120 Unfiltered Sensitivity relative to NO2 (%) 100 80 60 40 20 0 0 200 400 600 800 1000 1200 -20 -40 Time (s) 5 Linearity has been optimised by modifying the filter structure NO2-A42F (first filter material) and OX-A421 (improved) 200 180 160 Output (ppb) 140 120 100 80 60 40 20 0 0 20 40 60 80 100 c (ppb) 120 140 160 Humdity dependence for standard design and new design (0%, 25%, 0%. 50%, 0%, 75%, 0%, 90%rh) O3-B1 Humidity Transient Tests at 25, 50, 75 & 90% RH 08/08/2014 O3-B4 200 200 150 150 100 100 50 0 0 5000 10000 15000 20000 Output (nA) Output (nA) 50 0 0 -50 -50 -100 -100 500 1000 1500 2000 -150 -150 -200 -200 Time (/10s) Time (s) 7 NO is important for monitoring combustion and is very reliable 200 100 0 50 NO SNAQ 24 corrected (ppb) 100 50 0 NO SNAQ 24 (ppb) RMSE = 6.07 ppb 150 y = 0.63 ( 0.01 ) x + -10.21 ( 0.14 ) R2 = 0.92 150 200 (electrochemical vs reference) 0 50 100 150 200 NO reference (ppb) 0 50 100 NO reference (ppb) Cambridge Heathrow network sensors (Christoph Huelgin, EMPA) 150 200 VOCs Real time measurement PID, Metal Oxides, not selective but affordable Ion Mobility Spectroscopy (IMS): selective TDLS: selective, but costly and specific to one or a few VOCs VOC generator: 5+3 channel automated permeation tube/ DMFC system with rh control PID Lamp life: was 2,000 hours, now 10,000 hours and 1-2 ppb resolution Response to 100 ppm Isobutylene 120 Calibrated result normalised to 240 hours / % 110 Normalised to 240 hours 100 90 80 70 60 50 40 30 20 10 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Total lifetime burn hours 5000 5500 6000 Metal Oxides: p-type Sensitivity, LoD: CTO CTO response to 300 ppb Toluene, 50% rh (Ascending T) 3 normalised to 1 ppm T max, R/Ro(Tmax) 405°C, 6.8 R/R0 2.5 2 1.5 1 0.5 0 250 270 290 310 330 350 370 390 410 430 450 430 450 Te mp (°C) CTO response to 1 ppm Benzene, 50% rh (Ascending T) 2.5 2.25 2 1.75 1.5 1.25 1 0.75 0.5 250 360°C, 1.2 2 380°C, 1.5 1.75 R/R0 R/R0 CTO response to 4 ppm Methanol, 50% rh (Ascending T) 1.5 1.25 1 0.75 270 290 310 330 350 370 390 410 430 0.5 250 450 270 290 310 330 Te mp (°C) 350 370 390 410 Te mp (°C) CTO response to 1 ppm CH2O, 50% rh (Ascending T) 3 CTO response to 750 ppb Acetone, 50% rh (Ascending T) 400°C, 2.0 2 1.5 5 1 4 0.5 3 0 250 R/R0 R/R0 2.5 270 290 310 330 350 370 390 410 430 415°C, 3.7 2 450 1 Te mp (°C) 0 250 CTO response to 500 ppb Ethylacetate, 50% rh (Ascending T) 270 290 310 330 350 370 390 410 430 450 430 450 4 3.5 3 2.5 2 1.5 1 0.5 0 250 CTO response to 750 ppb Acetone, 0% rh (Ascending T) 5 425°C, 4.0 4 R /R 0 R/R0 Te mp (°C) 3 370°C, 5.6 2 1 270 290 310 330 350 Te mp (°C) 370 390 410 430 450 0 250 270 290 310 330 350 Te mp (°C) 370 390 410 Metal Oxides: n-type WO3 response to 300 ppb Toluene, 50% rh (Ascending T) 1.5 1.4 R/R0 Sensitivity, LoD: WO3 1.3 390°C, 2.0 1.2 1.1 normalised to 1 ppm 1 250 270 290 310 330 350 370 390 410 430 450 430 450 Te mp (°C) WO3 response to 4 ppm Methanol, 50% rh (Ascending T) 1.5 340°C, 1.05 1.4 1.5 1.4 1.3 R/R0 R/R0 WO3 response to 1 ppm Benzene, 50% rh (Ascending T) 1.2 1.3 370°C, 1.4 1.2 1.1 1.1 1 250 270 290 310 330 350 370 390 410 430 1 250 450 Te mp (°C) 270 290 310 330 350 370 390 410 Te mp (°C) WO3 response to 1 ppm CH2O, 50% rh (Ascending T) 380°C, 1.3 1.5 WO3 response to 750 ppb Acetone, 50% rh (Ascending T) 1.3 1.2 R/R0 R/R0 1.4 1.1 1 250 270 290 310 330 350 370 390 410 430 450 Te mp (°C) 1.6 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 250 340°C, 1.4 270 290 310 330 WO3 response to 500 ppb Ethylacetate, 50% rh (Ascending T) 370°C, 2.0 1.4 R/R0 R/R0 1.5 370 390 410 430 450 430 450 WO3 response to 750 ppb Acetone, 0% rh (Ascending T) 1.7 1.6 350 Te mp (°C) 1.3 1.2 1.1 1 250 270 290 310 330 350 Temp (°C) 370 390 410 430 450 1.6 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 250 360°C, 1.2? 270 290 310 330 350 Te mp (°C) 370 390 410 Particulates • Well-known health dangers • Urban air and IAQ problem • PM10? Now PM2.5 and soon Ultrafines <300nm (PN, not PM?) TEM Images – Aggregated nanoparticles 15 nm Aggregate 15 nm Aggregate 30 nm Aggregates 20nm Optical Particle Counter OPC-N2: PM1, PM2.5, PM10 -0.38 to 17 µm -Particle size histogram each second -PM calculated every second -Aerodynamic flow, fan control for clean optics in dirty environments Operated at Heathrow for 22 months 70g weight, 130mA/5V, €325 Other measurements: size speciated PM Particle count Size bin (0.4 – 15 µm) time Comparison with reference instruments (Paul Kaye, Paul Williams) Size speciated PM: inlet calibration Dominated by small aerosol sizes Urban air and IAQ motes • Boxes? Motes? • Wired, wireless, solar powered • Modular to adapt tp specific IAQ, urban, rural and nuisance odour networks Fixed Site Motes 2010-2014 City-wide network in Cambridge 2010 High density network at Heathrow airport 2011-2013 FP7 project to detect bomb factories: 14 gas/ VOC sensors 2011-2013 Indoor motes