Overview
ISO 16258-1:2015 - "Workplace air - Analysis of respirable crystalline silica by X‑ray diffraction - Part 1: Direct‑on‑filter method" specifies a laboratory and field‑compatible procedure for measuring respirable crystalline silica (RCS) collected on air sampling filters. The method uses X‑ray diffraction (XRD) to analyse dust deposited directly on a 25 mm sample filter. The standard covers instrumental parameters, sampling and analytical practice, and corrections needed to report reliable RCS concentrations for occupational exposure assessment.
Key topics and technical requirements
- Scope and target analytes: Applies to RCS (primarily quartz and cristobalite); less common polymorphs (e.g., tridymite) are excluded due to lack of reference materials.
- Sampling fundamentals: Requires air samples collected on 25 mm filters; describes samplers, filters, pumps, flow meters and transport/storage of samples.
- Analytical procedure:
- Direct analysis of filter deposits by XRD, with guidance on instrumental and scan parameters for common detector types.
- Gravimetric determination of respirable dust mass (pre‑ and post‑weighing).
- Preparation and use of calibration curves, standard reference materials and drift‑correction samples.
- Corrections for absorption effects and sample treatment to optimise results.
- Performance characteristics: Addresses limit of detection (LOD), minimum detectable value (MDV), limits of quantification (LOQ) and measurement uncertainty. Notes that under low dust loads or low silica content the method may not meet expanded uncertainty criteria of EN 482.
- Reporting: Specifies required content for a test report to support occupational hygiene decisions.
Applications and practical value
- Used by industrial hygienists, analytical laboratories, and occupational health professionals to:
- Assess worker exposure to respirable crystalline silica in industries such as mining, construction (concrete cutting, drilling), foundries, glass/ceramics, sandblasting and stone fabrication.
- Verify effectiveness of engineering controls, respiratory protection and work practices.
- Support regulatory compliance and exposure monitoring programs.
- The direct‑on‑filter XRD approach reduces sample preparation steps and preserves information about the sampled aerosol for rapid routine analysis.
Who should use this standard
- Occupational hygiene laboratories performing RCS quantification by XRD.
- Employers and consultants establishing silica monitoring programs.
- Regulatory bodies and proctors validating laboratory methods for workplace air analysis.
Related standards
- ISO 24095 - Guidance for the measurement of respirable crystalline silica (recommended companion document).
- ISO 7708 - Particle size fraction definitions (respirable convention).
- ISO 13137 - Requirements for personal sampling pumps.
- ISO 15767 - Controlling and characterizing uncertainty in weighing collected aerosols.
Keywords: ISO 16258-1, respirable crystalline silica, RCS, X‑ray diffraction, direct‑on‑filter, workplace air, silica analysis, 25 mm filter, occupational exposure.
