Particulate matter consists of any particles suspended in ambient air. In general, they consist of a complex mixture of substances of different sizes and characteristics, depending on the origin of emissions. In addition to the measurements of particulate matter in the telemetry network, which are used to inform the population in real time, PM10 and PM2.5 particulate matter are also measured by the filter reference method. Differences between the results of telemetry network measurements and those obtained with the reference method are due to different measurement methods.