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How to monitor pollution in Low Emission Zones

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Low Emission Zones (LEZs) are designed to monitor and improve the levels of air and noise pollution caused by road traffic, and in particular the combustion processes of vehicles circulating in large cities. In Europe the legislation aims to regulate and harmonise the minimum requirements for pollution control devices and systems.

LEZ monitoring points

Under Europe legislation, local authorities must establish a continuous monitoring and follow-up system to ensure compliance with air and noise quality objectives in LEZs.

Required emissions and noise levels

Legislation explicitly identifies the pollutant parameters that are the focus of emissions from the vehicles that make up road traffic. Specifically, it establishes the obligation to measure nitrogen dioxide (NO2), particulate matter PM 2.5 and PM10, and sound pressure levels Laeq, LAmax and Lden.

Data collection. Equipment to ensure data quality and avoid legal issues.

The validity of the data on pollutants in the LEZs is taken into account by the European and national monitoring authorities, as well as by the citizens.

In order to ensure the legal validity of the data, the LEZ legislation from some countries stipulates the following (although this may vary from country to country):

For NO2, measurements will have an uncertainty of 15%.
For PM10 and PM2.5, they will have an uncertainty of 25%.
For fixed measurements, data collection must be at least 90%.
For indicative (temporary) measurements, data coverage shall be at least 90% for 8 weeks evenly distributed over the year.
All measurements must be traceable in accordance with UNE-En ISO/IEC 17025, applicable to tests and calibrations.

Estación compacta de medida de calidad del aire

Data quality and compilation.

In addition to having reference equipment that guarantees that the measurements meet certain standards, it is necessary to check the quality of the data sent by the equipment itself before sending it to the local authorities or other public administrations:

Periodic maintenance of the equipment that collects data in the municipalities.
Calibration through an accredited European body.
Periodic verification of the uncertainties required by the legislation.
Manual verification of the data received.
Recording of exceedances and activation of alarms.

validación datos

Communication with public authorities and citizens.

LEZ legislation stipulate the need to inform the authorities. In particular, they must:

Publish reports assessing compliance with the objectives and monitoring indicators.
Send reports and records of exceedances at the stations to the national or European administrations.

Communication obligations to the public are also included, including:

Daily updated information on NO2 concentrations, particulate matter and observed exceedances.
Open data communication through clear and accessible means (web, social networks…).

Panel informativo Ayuntamiento

Low emission zone stations and equipment

test