Brunel ABS320 for phase contrast particle counting. Brunel Asbestos

Fibre Counting Training Software©.  

Asbestos Microscopy

The microscopy requirements for the identification and particle counting of asbestos are exacting, and are covered by the Health and Safety Guidance (HSG) 248 Appendices 1 and 2 of the Health and Safety Executive (HSE). is an excellent resource for up to date information and further references. Microscopy in relation to asbestos should involve the use of a good quality stereomicroscope for gross specimen sampling, the identification of fibres with polarising microscopy/dispersion staining and particle counting with a phase contrast microscope.


1. A low power, good quality zoom stereomicroscope should be used for the initial search of samples for suspected fibres. Brunel Microscopes recommends the BMZ stereomicroscope series for this purpose.

2. For the identification of asbestos fibres by polarised light microscopy (PLM), a polarising microscope capable of Kohler illumination with a dispersion staining objective such as a McCrone dispersion lens with a x10 magnification is required. This aids the assessment of fibre refractive indices by producing intense dispersion staining colours. The Brunel SP300P polarising microscope fits the specification described.

3. Asbestos particle counting by phase contrast microscopy has very specific requirements, and there are relatively few microscopes that can meet the phase contrast optical performance criteria. This is measured with a Phase Contrast Test Slide that was developed by the Health and Safety Laboratory (HSL) on behalf of the HSE and in collaboration with ULO Optics (formerly PTR Optics) and the National Physical Laboratory (NPL). The slide is known as HSE/NPL Test Slide, and its purpose is to provide a reproducible phase object to check the suitability of microscope phase systems for asbestos fibre counting. The test slide has 7 bands of 20 lines each, and the width of the lines in each band decreases. The master engraving was produced by the NPL using a ruling engine, and each of the HSE standard test slides is an epoxy replica of the NPL master. HSL certifies the test slides as satisfactory for use to set up phase contrast microscopes and categorises them into two groups

1. Those that have band 4 lines fully visible and band 5 partially visible - these are given red documentation

2. Those that have band 5 fully visible and band 6 partially visible - these are given green documentation.

Any suitable microscope must be able to resolve either band 4 on a red label slide (with maybe parts of band 5 visible) or band 5 on a green label test slide (with maybe parts of band 6 visible). The x40 phase objective with a x12.5 eyepiece with a Walton and Beckett graticule is the required combination.

The Brunel ABS320 meets this standard using test slide 6609 certificated and confirmed by the HSL. We believe that it is the lowest price microscope on the market to do so.

The use of the test slide is required by the HSE to ensure microscopes are properly adjusted when testing for compliance with the UK asbestos control limits.

Specialised Microscopes

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The Brunel ABS320 trinocular  microscope complies with the test slide reading required by the Health and Safety Executive for asbestos fibre counting. These are robust industrial microscopes finished to a very high standard and with a very modern design. The light source is a Kohler LED unit integral to the base of the microscope. This makes the microscope an ideal instrument for phase contrast applications, and the trinocular ABS320 is, we believe, the lowest priced phase contrast microscope that meets the HSE specification for asbestos fibre counting that is currently available.

A particular feature is the large rectangular mechanical stage with drop down co-axial controls. The ABS320 is specifically configured to provide the optical specifications needed for asbestos fibre counting. This consists of infinity corrected x10, x20 and x40 plan brightfield phase contrast objectives together with an easy to operate slider phase ring system in the condenser. This allows an easy change ‘toggle’ movement from x10 to x40 phase contrast presentation. For those who may want a full magnification range in phase contrast, a Zernicke phase condenser and further phase contrast objectives are available as accessories. x12.5 eyepieces, one with a focusing Walton and Beckett graticule, green interference filter and a centring phase telescope complete the specification.

The co-axial coarse and fine focus controls have a graduation reading in 2 microns. The total focus range covers 35mm and the movement runs in extra wide precision ball-bearing hardened steel tracks. Tension adjustment and safety auto focus stop units are fitted as standard.

The specific feature of the Brunel ABS320 series is the potential flexibility, both in optical performance and image capture systems. We believe that at this budget there is no other microscope that can offer this flexibility and excellent results with phase contrast microscopy, together with green certification for asbestos fibre counting. There is an excellent carrying case with suitcase style handle and wheels which makes the ABS320 truly portable.

Price ABS320 Trinocular microscope - £1920.83 + vat complete for fibre counting

We are also able to supply complete systems that include an HDMI camera and laptop preloaded with our own exclusive Walton and Beckett software - please contact us for more details.

Brunel ABS320

Brunel ABS320

Brunel Microscopes Ltd

Registered in U.K. (England) No: 2060047

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Microzoom CCTV Units

Vision Mantis Inspectoscope

Comparison Microscopes

Whole Blood Analysis

MC1 Microscope

HSL test slide bandings

Brunel ABS320

Brunel ABS320 Carrying Case

x10 widefield eyepieces - pair   ABS320-01


Measuring eyepiece                 ABS320-05


Stage micrometer                    ABS320-02


Aluminium carrying case          ABS320-04


CCTV adapter                         ABS320-03


SLR photography adapter         ABS320-07


Brunel ABS320 accessories

RICE slide image with Walton and Beckett graticule overlay

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Brunel Asbestos Fibre Counting Software©

Asbestos is potentially a very dangerous material and has to be handled by individuals that have been trained and accredited to  UKAS standards to be safe to undertake this type of analysis. UK laboratories are required to be accredited by the United Kingdom Accreditation Service (UKAS) to ISO 17025 to undertake this particular analysis as part of assessing clearance under the Control of Asbestos Regulations (CAR). Participation in RICE in the United Kingdom is recommended in the Health and Safety Executive's Guidance - HSG 248, "Asbestos: The analyst's guide for sampling, analysis and clearance procedures" and is a precondition for accreditation of this analysis to ISO 17025.


The Regular Inter laboratory Counting Exchange (RICE) PT scheme assesses the proficiency of laboratories and individuals counting asbestos fibres in air.The RICE scheme is operated by HSL, which oversees management, registration, and membership matters together with distribution of the samples and processing the participant data.

The essential element of the phase contrast fibre counting part of the process is controlled by the Walton and Beckett eyepiece graticule.

Brunel Asbestos Fibre Counting Software©

Training in the recognition of fibres and structures produced by air filtration is at the core of the whole legislation covering the identification and removal of asbestos. One of the difficulties is being sure that the trainee is seeing the same particle as the trainer during the learning process. The Walton and Beckett graticule is part of the x12.5 eyepiece and cannot therefore be seen in live images captured by cameras attached to the trinocular phototube of the microscope. Our own IT team has addressed this issue and our Asbestos Fibre Counting Software overlays live images provided by a digital camera, that is capable of visualising the test slide bands, attached to the microscope (our own HDMI Digicam is ideal). The size of this overlay provides an image identical to that seen down the microscope in size and area covered. This allows the trainer to discuss with the trainee the finer points of recognition with both being confident that they are looking at the same thing. The software is customised to ensure correct positioning and size for each microscope/camera system and computer by our own IT staff, and the license price includes this commissioning

Brunel Asbestos Fibre Counting Software License  -  £296.67 + vat for each system


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