Monitoring & metering


quality across one of the world’s major cities. With over 100 AQMesh ‘pods’ located across the city, the Breathe London partners were, for the first time, able to provide hyperlocal detail on London’s air quality. At the end of the two year period, the entire network continued to operate for a further five months in a separate project funded by NERC/UKRI and managed by Prof. Rod Jones (University of Cambridge) and colleagues. Each AQMesh pod contained small low-cost


Breathe London pilot verifies ‘small sensors’ T


he Breathe London pilot project ran over two years from October 2018; monitoring and characterising air


Breathe london objectives


1. Advance the use and development of innovative, lower-cost monitoring techniques to support cities around the world;


2. Enhance London’s existing regulatory network to better understand pollution and assess targeted solutions for cleaner air, like the Ultra-Low Emission Zone (ULEZ); and


sensors, developed and manufactured in the UK by Alphasense. The company’s Arthur Burnley says: “One of the main objectives of the project was to evaluate the utility of small sensors, so we were delighted that they performed so well, and hope that this will provide other cities with the confidence to invest in their own networks.” In addition to the pods, Breathe London


also equipped Google Street View cars with reference-grade monitors, which together with the pods, complemented and expanded London’s existing regulatory monitoring network.


The air qualiTy moniToring dilemma Historically, air quality monitoring has relied upon expensive, highly accurate and reliable reference- grade air quality monitors that are often located in large air-conditioned, mains powered cabinets. As a result of their size and the requirement to be installed in urban areas, these systems sometimes require planning permission and can be difficult to locate in ideal locations. In addition to their large capital cost, reference


stations also incur large operational costs for maintenance and calibration work. Nevertheless, reference stations perform an essential role in providing accurate reliable data for comparison with air quality standards - especially for


particulates and nitrogen dioxide (NO2). They also provide a reliable method for temporal and spatial air quality comparisons. The air quality dilemma is therefore that


reference stations are so costly that they have to be located sparsely. Consequently, they are unable to deliver granular local data, so operators have to rely on modelling. The Breathe London project was therefore established to help resolve this dilemma. Data from the project have now been fully


evaluated and one of the partners, Environmental Defense Fund (EDF), has published a summary entitled: The Breathe London Blueprint: How cities can use hyperlocal air pollution monitoring to support their clean air goals.


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3. Make air pollution data publicly available and visualise it in new and innovative ways.


The Breathe London pilot met and surpassed


these objectives. London Mayor Sadiq Khan says: “These findings, from our world-leading Breathe London sensor network, are a stark reminder that pollution hotspots exist across London and will refocus our efforts on improving air quality for all. As we face up to the current climate emergency, I hope the success of this scheme will act as a blueprint for cities around the world to battle their own toxic air emergencies.”


1. innovative, lower-cost monitors


Any city considering the use of lower-cost sensors will be keen to learn whether they can provide reliable data and insights. The Breathe London Blueprint concludes: “Yes - you can use emerging monitoring technologies and techniques to identify and characterise air pollution.” Breathe London data produced insights


that were broadly comparable to findings from London’s extensive regulatory network, demonstrating that lower-cost sensor systems and mobile monitoring are valid options for generating useful data.


2. Solutions for cleaner air


Even towns or cities with limited access to reference-grade air quality monitors can assess pollution levels and find ways to improve air quality. For example, lower-cost sensor systems can help find air pollution ‘hotspots,’ or the places and times of day that need the most attention. These sensors can also provide flexible tools for assessing the effects of air quality intervention measures.


November 2021 Instrumentation Monthly


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