NBN ISO 13794:2021

This document specifies a reference method using transmission electron microscopy for the
determination of airborne asbestos fibres and structures in in a wide range of ambient air situations,
including the interior atmospheres of buildings, and for a detailed evaluation for asbestos structures
in any atmosphere. The specimen preparation procedure incorporates ashing and dispersion of the
collected particulate, so that all asbestos is measured, including the asbestos originally incorporated
in particle aggregates or particles of composite materials. The lengths, widths and aspect ratios of the
asbestos fibres and bundles are measured, and these, together with the density of the type of asbestos,
also allow the total mass concentration of airborne asbestos to be calculated. The method allows
determination of the type(s) of asbestos fibres present. The method cannot discriminate between
individual fibres of the asbestos and elongate fragments (cleavage fragments and acicular particles)
from non-asbestos analogues of the same amphibole mineral[12]
.