The results of the 2019 AIRLAB Microsensors Challenge* were revealed in Paris on 21st January and AQMesh was awarded the highest score for accuracy of all products presented for monitoring of outdoor air quality.
AQMesh is the only small sensor air quality monitoring system that can demonstrate its performance across extensive global co-location comparison trials now spanning more than 7 years. AQMesh pods have been operating out in the field since 2012 next to certified reference equipment, in real applications, in real conditions, across all environments, throughout all seasons, for months rather than weeks or days.
During that time, improvements in electrochemical sensors and the unique, carefully developed, fully traceable AQMesh processing algorithms have given a dramatic improvement in performance and accuracy with AQMesh.
The table below shows how the correlation coefficient achieved for NO2 has improved significantly since AQMesh was first launched.
|Version||Production date||NO2 sensor||Characterisation||Online processing||Typical R2*||Typical MAE**|
|V3.0||Jan 2013 – Dec 2014||Significant O3 cross-gas effect||Manufacturer’s data||Correction for cross-gas effects and environmental factors||0-0.03||Requires scaling|
|V3.5||Jan 2015 – Oct 2015||O3-filtered||As V3.0||Correction for cross-gas effects and environmental factors||0.1-0.7||Requires scaling|
|V4.0||Jan 2015 – Oct 2016||As V3.5||Manufacturer’s data and characterisation at factory||Correction for cross-gas effects and environmental factors||0.5-0.8||Requires scaling|
|V4.1||Limited release||As V4.0||Factory characterisation and quality check||More sophisticated corrected for cross-gas effects and environmental factors||0.7-.095||Dependent on variance between sensors|
|V4.2||Oct 2016 – Dec 2018||O3-filtered and improved response at higher ambient temperatures||Factory characterisation, quality check, accuracy and precision tests||As V4.1, but with optimised electronic setup and performance enhancements below the limit of detection||>0.8||<5ppb|
|V5.0||Jan 2019 – Jul 2019||O3-filtered with new design and improved response to a wider range of conditions||As V4.2||As V4.2, but optimised performance across a wider range of temperatures||>0.8||<5ppb|
|V5.1||Jul 2019 – current||As V5.0||As V5.0||As V5.0, but optimised further below the limit of confidence||>0.85||<5ppb|
R2 of >0.6 for NO2 is generally considered to be a strong enough performance.
*Readings at 15 minute average intervals.
**Typical prescaled variance.
A new paper published by the American Chemical Society (ACS Sensors) reviews the use of amperometric electrochemical gas sensors for monitoring inorganic gases that affect urban air quality.
Recent co-location comparison trials using the latest AQMesh processing (v4.2.3) have further proven AQMesh performance with impressive R2 values in excess of O.8 and 0.9 for NO2 in Benelux, Slovakia and Spain.
The small sensor air quality monitoring world has moved on during the last three years and we have identified several new challenges and benefits relating to the continual development of air quality monitoring technology.
At the IAPSC in May 2017, Professor Rod Jones of the University of Cambridge presented his case study on large scale deployment of sensors, which included showing how AQMesh can be used to discriminate between local sources of pollution and regional sources of pollution.
At the RSC AAMG event on ‘Air Quality Monitoring: Evolving Issues and New Technologies’ Professor Rod Jones of the University of Cambridge presented a paper showing very encouraging results.