Measurement errors

When researching the content of suspended particulate manner in the air, one has to be aware that there is a number of factors interfering with the measurements. For most measuring methods in which the amount of air flowing through the chamber is registered, the test depends on the temperature, humidity, and atmospheric pressure. Some professional sensors include additional temperature, humidity, and pressure measurements, in order to correct the initial measurement.

 

Main problem – the irregularity of the shape of the particles and determining the substitute diameter, is common for all measuring methods. In the case of a need to determine and classify the particles – basing on the shape and/or mass – advanced methods of filtration and analyzing are being used. However, one has to remember that the air surrounding us, includes all types of particles – that is why it is extremely important to adjust the measurement and filtration methods to the aim of the measurement.

 

It is needed to be stressed out that the measurement of suspended particulate matter is local and temporary. This means that two nominally identical sensors may show different levels of particulate matter in two different locations. Furthermore, the content of particulate matter in the air – and thus sensor measurements – change in time. Some measurement methods (for example the gravimetric method) prevent the temporary measurement of particulate matter concentration, allowing to measure the average pollution concentration (for example daily).

 

The vast majority of measurement methods use various electronic devices to carry out the measurements. It’s worth remembering that using even the most expensive measuring method, does not guarantee the correctness of the results. Many factors concerning the electronic system impact the correctness of the measurement, such as for example the accuracy of the analog-digital converters, device power stability, the temperature of the electronic system, and many more.

 

Currently, there are no methods of local temporary referential measurements, which could be carried out outside a laboratory, or they are very expensive. Each measuring method is characterized by errors resulting from the technology, location, or time of measurement. Let the comment concerning the accuracy of measurements be constituted by the fact that non-referential measurement methods for PM10 are regarded as equal in reference to referential methods at the divergence below 25%. To sum up, let us quote John M. Keynes “It is better to be roughly right than precisely wrong”!

Systematic air quality measurements in Poland – in terms of the State Environment Monitoring, started at the beginning of the 90s (20th century) and gradually developed. Currently, the methodology which is being used is specified by the resolution of the European Parliament and Council 2008/50/WE dated May 21st 2008 concerning the air quality and cleaner air for Europe (Official Journal of the European Union L 152 from 11.06.2008, page 1) and the decree of the Ministry of Environment dated September 13th 2012 concerning assessing substances in the air (Journal of Laws from 2012, item 1032).