The particle size fractions sampled in environmental science are different from those sampled
for occupational hygiene work. The target specification for instruments sampling the respirable
fraction for occupational hygiene purposes is specified in EN481 (1993) and is based on
sampling a distribution of particles (approximately < 10 µm) with a median diameter of 4.3 µm,
whilst the environmental fractions have are based on particle distributions with median
diameters of 10 µm (PM10) and 2.5µm (PM2.5). The relationship between the three different
dust fractions is shown in Figure 1