Breathe London pilot verifies small sensor air quality monitoring for smart cities with AQMesh

The Breathe London pilot, which used 100 AQMesh pods as part of a ground breaking city-wide network of air quality monitoring stations, proved that small sensor monitoring technology can be deployed successfully to give results comparable with those of reference equipment.

An independent audit of the quality assurances and control procedures for the Breathe London network, conducted by National Physics Laboratory (NPL), has been published and highlighted encouraging results for AQMesh performance.*

Overall, a mix of comparison methods was used to scale and quality control the whole network, including AQMesh co-location with reference - the gold pod method - and Professor Rod Jones’ network calibration scaling method. The gold pod method, as developed by AQMesh, featured extensively and provided R2 values over 0.9 for both NO2 and PM2.5. NPL found that “the activities conducted for the audit purpose and the associated findings revealed a strong adherence of the data processing and management to the Breathe London QA/QC requirements.”*

The initial phase of the Breathe London project aimed to map air pollution across the city at an unprecedented level of local resolution, in order to develop a revolutionary air quality monitoring template that could then be replicated in cities across the globe.

As part of the project the AQMesh pods were installed at different locations throughout London, monitoring key pollutants in near real-time, including nitrogen dioxide (NO2) and fine particulate matter (PM2.5). The data collected by AQMesh was then published on a live interactive map showing current pollution levels across the city.

Data gathered during this pilot phase was successfully used to evaluate and inform public policies to mitigate sources of pollution, including monitoring the impact of the world’s first Ultra Low Emissions Zone (ULEZ). The network of AQMesh pods first established a baseline of pollution levels ahead of the ULEZ’s introduction, which began in central London on 8th April 2019. A combination of the data from AQMesh and two Google Street Cars, fitted with mobile monitoring equipment, was then used to assess the impact the ULEZ was having on ambient pollution levels. Initial analysis of the network data found that concentrations of NO2 had reduced by approximately 13% when compared with the same period in the previous year.

The network was also able to identify new pollution hotspots, such as a bus garage which had not been picked up by previous monitoring and modelling efforts, despite being a significant source of NO2.

Covid-19 confinement regulations in March 2020 gave new insight into London’s pollution, with the network’s AQMesh pods reporting significant NO2 reduction immediately after restrictions were introduced.

This successful pilot phase of Breathe London has also led to the Environmental Defense Fund (EDF) publishing a ‘blueprint’ for other cities planning a hyperlocal air quality monitoring network. The guide for aspiring smart cities highlights a range of considerations for choosing small sensor systems and deploying them as a city-wide network.

Using the blueprint, global cities could deploy networks of such systems to identify and quantify air pollution in order to develop, implement and assess mitigation strategies.

^{*Section 4.1: NPL REPORT EAS (RES) 001 “AUDIT REPORT ON BREATHE LONDON FIXED NETWORK QUALITY ASSURANCE AND QUALITY CONTROL PROCEDURES”}

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