HSE Test Slides
The HSE Test Slide was developed by the Health & Safety Laboratory in collaboration with ULO Optics on behalf of the Health & Safety Executive. It’s purpose is to provide a reproducible phase object to check microscope performance prior to asbestos fibre counting. It is used alongside the S12 Stage Micrometer.
Daily use of the slide is required in many international methods including those attached to the European Directive on Worker Protection against Asbestos (official journal on the European Connunities, L263, 24th September 1983). The slide is also required by the HSE to ensure microscopes are properly adjusted when testing for compliance with the UK asbestos control limits. This is described in HSG 248(A1.32). NIOSH have now approved the band 5 slides for use in the United States, provided it is used with ULO’s Optics’ instructions – the NIOSH reference method is not compatible with band 5 slides.
Description and Manufacture
The master engraving consists of seven bands of lines, with 20 bands in each band, progressively reducing in width and depth, from 1.1 microns to 0.25 microns wide. The bands are separated by 20 micron gaps. A test zone is delineated by a rectangle bounded by deep grooves, which can be viewed using a microscope with 100x magnification in either dark field or phase contrast mode.
Each of the HSE Test Slides is an epoxy replica of the master. An impression of the lines is produced in a resin of refractive index 1.58 and is mounted on a microscope slide. This impression is sealed in another resin of refractive index 1.485 and covered with a cover slip. To maintain a steady level of quality between slides, HSL assesses each one. The test zone is examined to assess the contrast and clarity of the bands. The whole slide is inspected for cracks, splits and other manufacturing defaults. HSL keep a recorded digital image of each slide.
ULO Optics recommends that all slides are retested after 5 years due to possible band degradation.