I’ve sought clarification on this from HSE and this is the reply below which hopefully will help
HSG 248 2021 is as follows:
A2.30 ………It is recommended that ‘asbestos not detected’ is reported when no asbestos fibres or fibre bundles are found after careful searching of the sample under the stereo-microscope for around 10 minutes and searching a minimum of two extracted preparations mounted in suitable RI liquid at high magnification by PLM/PCM for a further 5 minutes. If during the search of the two ‘pinch’ samples by PLM only 1 or 2 fibres (or fibre bundles) are seen and identified as asbestos, the term ‘trace asbestos identified’ may be used. (The terms ‘asbestos not detected’ and ‘trace asbestos’ are defined in Box A2.1.) The analytical method is not quantitative and percentages of asbestos should not be reported.
Box A2.1 Definition of the terms ‘asbestos not detected’ and ‘trace asbestos’ The term ‘asbestos not detected’ should be reported when no asbestos fibres or fibre bundles are identified after the following analysis:
■ careful searching of the sample under the stereo-microscope for around 10 minutes; and
■ subsequent searching a minimum of two extracted preparations mounted in suitable RI liquid at high magnification by PLM/PCM for a further 5 minutes. If during the search of the two ‘pinch’ samples by PLM only 1 or 2 fibres or fibre bundles are seen and identified as asbestos, the term ‘trace asbestos identified’ should be used.
