Particle Sizes

Particle size plays a significant role in determining how particles behave indoors and their potential impact on human health. Fine particulate matter (PM2.5), with diameters of 2.5 micrometers or less, is a major concern due to its ability to penetrate deep into the respiratory system. An important subset of PM2.5 is ultrafine particles (UFPs), which have diameters less than 0.1 micrometers and are primarily emitted from combustion sources. These UFPs can even be transported to the brain via the olfactory nerve, potentially causing neurological effects. Particles in the 0.1 to 2.5 micrometer range can originate from indoor sources like soot or from the infiltration of outdoor particles. Coarse particles, larger than 2.5 micrometers, are mainly generated by mechanical processes like resuspending dust. These size distinctions are crucial because they influence a particle’s ability to penetrate indoors, remain airborne, and affect human health. For instance, the high surface area to mass ratio of UFPs makes them efficient at transporting harmful chemicals deep into the lungs. Understanding the sources and behavior of different particle sizes indoors is essential for developing effective strategies to mitigate their potential health risks.

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