HSG248 Asbestos: The Analysts’ Guide (Edition 2) – NORAC Thoughts on Bulk Analysis

We have had the updated version of HSG248 Asbestos: The analysts’ guide (edition 2) for a small number of weeks now but will still all be ploughing through to see ‘what has changed’. There were various comments made to highlight what appeared to be anomalies within the May 2021 version hence the need to re-release edition 2 in July 2021.

It would appear that some of the concerns regarding errors and anomalies have been addressed within the July version however some have not. Many will be aware of Jean Prentice and her long standing experience and expertise within the asbestos industry not least her microscopy and sample analysis skills.

As a valued member of the NORAC Management Committee Jean has provided her thoughts on Appendix 2. Jean has highlighted some errors and discrepancies which are still within the July 2021 edition 2 version so felt it was only right to raise awareness of this.

Colette Willoughby

NORAC Chairperson



The following is a summary of my thoughts on Appendix 2, HSG 248 (2nd edition 2021) which contains the method for analysis of materials for the presence of the 6 regulated varieties of asbestos (Appendix 7 contains further information for the analysis of soils).

This Appendix was assembled by a committee of volunteers called WG2, chaired by Garry Burdett (then of HSL but like me, since retired), many years ago: we thought it was finalised well over 12 years ago. It was issued for consultation in 2015 with some changes in the wording by persons unknown and further changes have now been introduced, some of which are questionable or technically inaccurate.

If you use this method, please note the following technical matters:

  • Paragraph 2.13 on the polarised light microscope, 7th Bullet point, states:

    “matched-pair binocular eyepieces of 8x or higher, one focusing (preferably non-rotatable). An eyepiece cross-hair graticule defining the vibration directions of the polariser and the analyser may also be used;”

    WG2 agreed that there is nothing technically wrong with a monocular polarising light microscope which does not require “matched-pair binocular eyepieces” but a focusing eyepiece with a crosshair (rotatable or otherwise) is essential as becomes apparent in later parts of the text (e.g. paragraph A2.32).

  • Paragraph A2.32 covers setting the microscope for Kohler or Kohler-type illumination. The 8th bullet point on examination of the back focal plane (setting the illuminating rays) states “…For Köhler or Köhler-type illumination the lamp filament should be in focus and completely fill the field of view (correct by adjusting the lamp housing)”.

    This sentence is technically incorrect as the lamp filament is NEVER visible with Kohler-type illumination. This error was introduced after the 2015 consultation.

  • The caption “Figure A2.3 RI liquid being placed on a glass slide” does not comply with best practice. The liquid should be “dropped” and not “placed”. There are multiple reasons for this and it is a skill that every competent microscopist should learn and apply.

  • Paragraph A2.7 (v) states “The different selected fibrous components are either identified using PLM, as one of the six regulated asbestos types, or determined to be non-asbestos”.

    This contradicts paragraph A2.4 “Other non-regulated amphibole minerals are also known to occur in the asbestiform habit but their identification is not within the scope of this document.”

    Such non-regulated minerals are still asbestos and, should they be found, reporting the sample as “NAD” is both technically incorrect and irresponsible. There are also non-amphibole mineral fibres with the characteristics of asbestos. I once found very fibrous vermiculite in plaster.

    There is no information given on investigating and/or reporting non-regulated asbestos and, although the current occurrence in materials is rare, there is always a potential for it to occur in imported materials or minerals. It is perhaps notable that the UK Asbestos Regulations 1969 only mentioned asbestos without further definition.


The two main aspects of the revised appendix which require implementation by the users are:

  1. Microscope usage: Correct setting up and usage of the polarised microscope is covered in detail. Both are critical to avoid misidentification, particularly when a “look alike” is present.Correct identification is easy with a well-set microscope and a little experience: commonly found materials such as shredded polyethylene, spiders webs, leather swarf etc., are different in relief, light absorption and/or birefringence and hence readily identifiable – or at least not falsely reported as asbestos (false positives).

  3. Additional treatment(s) of materials where fibres can be difficult to see or extract under the stereomicroscope: A variety of tests are available for use for these types of materials and some/all should be employed before reporting samples as “NAD”. It is up to the laboratory to design and justify its own procedures as different laboratories have different facilities and skill sets in both chemistry and microscopy (microchemistry can provide suitable methods of treatment and analysis).
    With a little thought and training such procedures should be easily adopted into routine analysis and avoid false negatives. These treatments are not required when fibres are extracted and positively identified as asbestos as noted in bold in paragraph A2.18 which states:

    Table A2.2 outlines the sample preparation treatments and techniques for various types of bulk material. One or more of these should be carried out whenever regulated asbestos types are not found in a material/product type that is known to have the potential to contain asbestos.”


The main question we should all be asking now is “Why haven’t we been doing this for the last decade or more?”. The information (without the technical errors) was available within HSE and in my opinion it should have been made available and implemented years ago.

I have great sympathy with all providers of technical services for asbestos who, within a short space of time, must digest and implement the entire contents of HSG 248 of which Appendix 2 is but a small part (although some will have already been using parts or all of the given information based on good practice and the 2015 discussion document).

Perhaps there should be a debate amongst the users regarding the issuing of guidance. Does a single document (with long publication delays and a massive short-term workload to ensure compliance) best meet our needs?

Would there be an advantage if each chapter and each appendix was separately issued and updated?

All suggestions welcome!

Jean Prentice

NORAC Management Committee


If you have any questions or suggestions pleasse head on over to our Technical Discussion forum here:


You can download this page as a pdf here: HSG248-NORAC-Bulk-Analysis-Review-Aug 2021