ISO/TC 146/SC 2/WG 7 - Silica

This document gives guidelines for the measurements of respirable crystalline silica in air using direct on‑filter or indirect X‑ray diffraction and infrared analysis methods, including quality aspects of the measurements. The scope of this document includes the following crystalline silica polymorphs: quartz and cristobalite.
These guidelines are intended for use in conjunction with the following specific analytical methods under the jurisdiction of ISO TC 146 SC 2: ISO 16258-1, ISO 16258-2, and ISO 19087. When used with any of these documents, this guidance will help to ensure measurement procedures meet the uncertainty requirements stipulated in ISO 20581, to enable the results to be compared to occupational exposure limit values (OELV) in accordance with EN 689[40].
These guidelines are also relevant to the analysis of filters obtained from dustiness measurements in accordance with EN 15051[1] and EN 17289[35].

This document is a standard for the analysis by Fourier-Transform Infrared (FTIR) of respirable crystalline silica (RCS) in samples of air collected on collection substrates (i.e. filters or foams). Three analytical approaches are described for whom the dust from the sample collection substrate is a) analysed directly on sampled filter, b) recovered, treated and deposited onto another filter for analysis, or c) recovered, treated and pressed into a potassium bromide (KBr) pellet for analysis. This document provides information on the instrumental parameters, the sensitivity of different sampling apparatus, the use of different filters and sample treatment to remove interference. In this document the expression RCS includes the most common polymorphs quartz and cristobalite. This document excludes the less common polymorphs of crystalline silica, such as tridymite. Under certain circumstances (i.e. low filter dust loads, low silica content), the analytical approach described in this method cannot fulfil the expanded uncertainty requirements of ISO 20581. Guidance for calculation of uncertainty for measurements of RCS is given in ISO 24095.

ISO 16258-2:2015 specifies the analysis of RCS in samples of air collected on collection substrates (i.e. filters or foams) by X-ray diffraction, when using an analytical approach where dust from the sample collection substrate (i.e. filter or foam) is recovered, treated and deposited on another filter for analysis by the instrument. This part of ISO 16258 includes information on the instrumental parameters, sensitivity of different sampling apparatus, the use of different filters, sample treatment to remove interference and correction for absorption effects. In this part of ISO 16258, the expression respirable crystalline silica includes the most common polymorphs quartz and cristobalite. The less common polymorphs of crystalline silica, such as tridymite, are not included within the scope of this part of ISO 16258 because a standard reference material is not available. Under certain circumstances (i.e. low filter dust loads, low silica content), the analytical approach described in this method may not fulfil the expanded uncertainty requirements of EN 482[7]. Guidance for calculation of uncertainty for measurements of RCS is given in ISO 24095.

This part of ISO 16258 specifies the analysis of respirable crystalline silica (RCS) in samples of air
collected on 25 mm-filters by X-ray diffraction, when using an analytical approach where the dust on
the air sample filter is directly analysed by the instrument. This part of ISO 16258 includes information
on the instrumental parameters, sensitivity of different sampling apparatus, uses of different filters
and correction for absorption effects. In this part of ISO 16258, the expression RCS includes the most
common polymorphs quartz and cristobalite. The less common polymorphs of crystalline silica, such
as tridymite, are not included within the scope of this part of ISO 16258 because a standard reference
material is not available. Under certain circumstances (i.e. low filter dust loads, low silica content), the
analytical approach described in this method may not fulfil the expanded uncertainty requirements of
EN 482.[5] Guidance for calculation of uncertainty for measurements of RCS is given in ISO 24095.