Particulate matter

What is particulate matter?

Fine dust is a complex, heterogeneous mixture of solid and liquid particles. The dust particles are only a few micrometers in size and therefore invisible to the human eye. The suspended matter is subdivided into the so-called PM categories, which differentiate particles according to their sizes. The term "Particulate Matter" is derived from the current definition by the US Environmental Protection Agency (EPA), which sets the "national air quality standard". 

When measuring particle sizes, the focus is on the respirable levels of immissions. The smaller the particles, the deeper they can get into the lungs and cause irreparable damage, which can lead to lung cancer. Suspended dust includes all airborne particles. These are subdivided into PM10, of which half of the particles have a diameter of 10 μm. The other half consists of PM2.5 with a particle diameter of 2.5 mm and smaller.  For example, modern laser processes emit particles in the range of nanometers, which is only one millionth of a millimeter. The concentration of the smallest particles is increasing steadily nowadays, while the number of greater particles is decreasing. This results to a rising danger to humans. 

The simulation of the internal airways allows the measurement of the particle concentration in the deposition process. Particles with an aerodynamic diameter of 10 micrometer are fully sucked into the inner airways to the bronchi. The evaluation of the larger particles is based on their percentage, which decreases with advancing size and reaches 0% at approximately 15 μm. Since 1997, the directive 2008/50/EG has been supplemented by PM2.5. It measures respirable particulate matter and defines ultrafine particles with a thermodynamic diameter of less than 0.1 mm.

In addition to the particle sizes, dusts can also be classified according to their nature, formation, physical properties, chemical compositions, shape or color. For example, other models determine the material’s structural toxicity or perpetrator. However, a full consideration is only possible with the inclusion of multiple models.