ISO 14966:2019 pdf download

ISO 14966:2019 pdf download.Ambient air — Determination of numerical concentration of inorganic fibrous particles — Scanning electron microscopy method
1 Scope
This document specifies a method using scanning electron microscopy for determination of the concentration of inorganic fibrous particles in the air. The method specifies the use of gold-coated, capillary-pore, track-etched membrane filters, through which a known volume of air has been drawn. Using energy-dispersive X-ray analysis, the method can discriminate between fibres with compositions consistent with those of the asbestos varieties (e.g. serpentine and amphibole), gypsum, and other inorganic fibres. Annex C provides a summary of fibre types which can be measured. This document is applicable to the measurement of the concentrations of inorganic fibrous particles in ambient air. The method is also applicable for determining the numerical concentrations of inorganic fibrous particles in the interior atmospheres of buildings, for example to determine the concentration of airborne inorganic fibrous particles remaining after the removal of asbestos-containing products. The range of concentrations for fibres with lengths greater than 5 µm, in the range of widths which can be detected under standard measurement conditions (see 7.2), is approximately 3 fibres to 200 fibres per square millimetre of filter area. The air concentrations, in fibres per cubic metre, represented by these values are a function of the volume of air sampled. The ability of the method to detect and classify fibres with widths lower than 0,2 µm is limited. If airborne fibres in the atmosphere being sampled are predominantly <0,2 µm in width, a transmission electron microscopy method such as ISO 10312 [8] can be used to determine the smaller fibres.
5 Principle
A sample of airborne particulate is collected by drawing a measured volume of air through a gold- coated, capillary pore track-etched membrane filter with a maximum nominal pore size of 0,8 µm, which is subsequently examined in the scanning electron microscope (SEM). Before analysis, the gold- coated filter is treated in a plasma asher to remove organic particles, to the extent that this is possible. The individual fibrous particles and constituent fibres in a randomly-selected area of the filter are then counted at a magnification of approximately 2 000×. If a fibre is detected at the magnification of approximately 2 000×, it is examined at a higher magnification of approximately 10 000× to measure its dimensions. At the higher magnification of approximately 10 000×, energy-dispersive X-ray analysis (EDXA) is used to classify the fibre according to the chemical composition. The limit of detection for this method is defined as the numerical fibre concentration below which, with 95 % confidence, the actual concentration lies when no fibres are found during the SEM examination. The limit of detection theoretically can be lowered indefinitely by filtration of progressively larger volumes of air and by examination of a larger area of the specimen in the SEM. In practice, the lowest achievable limit of detection for a particular area of SEM specimen examined is controlled by the total suspended particulate concentration remaining after the plasma ashing step. A limit of detection of approximately 300 fibres/m 3 is obtained if an air volume of 1 m 3 per square centimetre of filter surface area passes through the filter, and an area of 1 mm 2 of the filter area is examined in the SEM. This corresponds to an evaluated sample air volume of 0,01 m 3 .