ISO 13794 discusses ambient air with a focus on asbestos presence. ISO 13794 specifies a reference method using transmission electron microscopy for the determination of airborne asbestos fibres and structures 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. ISO 13794 describes the method that allows the determination of the types of asbestos fibres present.
Note: 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.
ISO 13794 on the determination of asbestos fibres is useful for:
Most fibres in ambient atmospheres are not asbestos and therefore, there is a requirement for fibres to be identified. Many airborne asbestos fibres in ambient atmospheres have diameters below the resolution limit of the optical microscope.
ISO 13794 is applicable to the determination of airborne asbestos in a wide range of ambient air situations, including the interior atmospheres of buildings, and for a detailed evaluation of any atmosphere. ISO 13794 is based on transmission electron microscopy, which has adequate resolution to allow the detection of small fibres and is currently the only technique capable of unequivocal identification of the majority of individual fibres of asbestos.
ISO 13794 describes the method of analysis for a single air filter. However, one of the largest potential errors in characterizing asbestos in ambient atmospheres is associated with the variability between filter samples. For this reason, it is necessary to design a replicate sampling scheme.
BS ISO 13794:2019 supersedes ISO 13794:1999, which is withdrawn. BS ISO 13794:2019 includes some technical changes with respect to ISO 13794:1999. These include:
ISO 13794