What is ISO 13794 - TEM for asbestos about?
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.
Who is ISO 13794 - TEM for asbestos for?
ISO 13794 on the determination of asbestos fibres is useful for:
- The construction industry / the housing industry
- Testing laboratories
- Health and safety personnel / building inspectors
- Quality control personnel
Why should you use ISO 13794 - TEM for asbestos?
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.
What’s changed since the last update?
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:
- The use of electronic display systems with measurement software is permitted
- The maximum particulate loading for TEM specimens is increased from 10 % to 25 %
- A simplified fibre identification procedure for investigation of known sources of the regulated asbestos varieties and richterite/winchite asbestos is permitted
- The reporting requirements have been changed to permit reporting of the concentrations of fibres and bundles longer than 5 μm and/or the concentrations of PCM equivalent fibres without the requirement to report the concentrations of structures equal to or greater than 0,5 μm
- There is no requirement to report the 95 % confidence intervals of the fibre concentrations
