EN 17289-1-2020 pdf download.Characterization of bulk materials – Determination of a size-weighted fine fraction and crystalline silica content – Part 1: General information and choice of test methods.
A.2 looks at the biases arising from the size distribution measurement and in particular: the biases arising from the different probability functions and the issues associated with the density of multicomponent particles. The biases arising from three scenarios of increasing complexity are compared with the ideal powder of a single mineral phase of crystalline silica. A.3 lists the uncertainties associated with the calculation method (EN 17289-2) and sedimentation method (EN 17289-3).
With any method of analysis representative sampling is extremely important. A recognized method or standard should be followed. The use of the methods specified in the sampling standards referenced in Iso 14488 and BS 3406-1, will allow the sampling uncertainty to be calculated.
A.2 Bias between EN 481 and sedimentation SWFF probability function and influence of density and mineral phase mass fraction
A.2.1 Bias between EN 481 and sedimentation SWFF probability curve
A.2.1.1 General
This subclause specifies the theoretical comparison between the respirable sampling convention and the SWFF probability function.
A.2.1.2 Ideal powder, one mineral phase of known density and ideal SWFF measurement
The SWFF and respirable sampling conventions have been compared theoretically for an ideal dispersed powder and ideal SWFF measurement (without bias or uncertainties) for which the particles have the following characteristics:
— all particles are spherical;
— all particles have an identical and known density;
— all particles (independent of size) are completely dispersed in air and test liquid, respectively;
— no particle is attached to (agglomerated with) any other particle, neither when dispersed in air nor when dispersed in the test liquid.
The comparison was carried out by calculating a bias map of the SWFF probability function / fraction relative to the respirable fraction for the aerodynamic mass-weighted particle size distributions specified in EN 13205-2 [14]. For such an ideal powder and an ideal measurement, it does not matter whether the SWFF was determined using EN 17289-2 or EN 17289-3.
For this ideal situation, the bias between the two sampling conventions is small, generally within ± S % except for particles greater than 6 pm where the bias is in the range from —5 % to —20 %. This is due to the sedimentation method not sampling particles of more than 6 pm aerodynamic diameter (dae).
A.2.2.2 ideal powder, two mineral phases of known density and ideal SWFF sedimentation measurement
The SWFF I and SWFF 2 have been compared theoretically for ideal dispersed powders and ideal SWFF measurement (without bias or uncertainties) for which the particles have the following characteristics:
SWFF 1:
— all particles are spherical;
— all particles have one mineral phase;
— all particles have an identical and known density (quartz density);
— all particles (independent of size) are completely dispersed in air and test liquid, respectively;
— no particle is attached to (agglomerated with) any other particle, neither when dispersed in air nor when dispersed in the test liquid.
SWFF 2: same as SWFF 1 except for:
— all particles have two mineral phases, one of them being quartz. All particles have the same mass fraction of quartz to total mass of the particle (independently of particle size).
— all particles have an identical and known density (density based on the densities of the two mineral phases and their mass ratio);
If the density of phase 2 for SWFF 2 is smaller (e.g. sepiolite 2 000 kg/rn3) than the quartz density, the calculated bias of SWFF 1 (defaulting density to quartz) compared to SWFF 2 (taking into account the real density of the two mineral phases) is positive. This was calculated for quartz mass fraction of25%,50%and 75%.
if the density of phase 2 for SWFF 2 is larger (e.g. rutile 4 200 kg/rn3, or magnetite 5 200 kg/rn3)
than the quartz density, the calculated bias of SWFF 1 (defaulting density to quartz) compared to
SWFF 2 (taking into account the real density of the two mineral phases) is positive for quartz mass
fraction of 50 % and 75 %. For quartz mass fraction of 25 %, the bias is negative and ranged from 0 %
to —5 %.
For very large mass median aerodynamic diameter (MMAD). the bias can reach very high negative values for very narrow size distributions, i.e. with GSD = 1,25. Even though the bias is large it is not relevant for SWFF measurements since SWFF is very low for samples with very large MMAD.
Large positive bias (root-mean-square bias > 0,10) occurs when the true particle density is overestimated, especially for the high quartz mass fraction (0,75).EN 17289-1-2020 pdf download.

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