**A.1 Filtration equipment**

The collection of microparticles with fibrous shapes is performed on one or more filters with porosity lower than the minimum diameter of the fibers used for the standard.

Equipment:

	- Filter materials: silicon, alumina, PC gold coated, cellulose acetate nitrate, or any other material with a circular or square shape.
	- The filter diameter is a choice of the lab depending on the filtration apparatus and on the spectrometer capability/availability.
	- However, in prEN ISO 4484-2 method, filter size and porosity are as follows:
	- In the case of <sup>μ</sup>-FTIR (reflection and transmission) analysis, the possible filters that can be used have a pore size not exceeding 5 μm.
	- In the case of <sup>μ</sup> Raman filters, the pore sizes that can usually be used are 0.45 μm, 0.8 μm, 1 μm, and 5 μm.
	- Vacuum pump (vacuum system filtration of 47 mm, 25 mm, 13 mm diameter, or any other diameter depending on the used filter diameter).
