ISO 21438-3:2010

Overview

ISO 21438-3:2010 specifies a validated laboratory and field method for measuring the time-weighted average (TWA) concentration of hydrofluoric acid (HF) and soluble particulate fluorides in workplace air. The method collects particulate fluorides on a pre-filter and HF on an alkali‑impregnated filter, followed by analysis using ion chromatography. It applies to personal (inhalable fraction per ISO 7708) and static (area) aerosol sampling and is intended for occupational exposure assessment.

Keywords: ISO 21438-3:2010, hydrofluoric acid, particulate fluorides, ion chromatography, workplace atmospheres, air monitoring.

Key topics and technical requirements

• Scope & applicability
  • Measures soluble particulate fluorides only (solubility defined by the specified sample preparation).
  • Designed to determine TWA mass concentrations for occupational exposure monitoring.
• Sampling design
  • Personal sampling of the inhalable fraction (ISO 7708) and static sampling supported.
  • Two-filter approach: pre-filter for particulate fluorides; alkali-impregnated filter for HF.
• Analytical method
  • Quantification by ion chromatography with calibration, blanks, and linear dynamic range procedures.
  • Sample dissolution and preparation steps precede analysis (reagent, field and laboratory blank controls required).
• Performance and ranges
  • Mass ranges per sample: particulate fluorides ~0.005 mg to ≥1.25 mg; HF ~0.0125 mg to ≥1.2 mg.
  • For a 120 L air sample, working concentration ranges are approximately:
    • Particulate fluorides: 0.04 mg·m⁻³ to ≥10 mg·m⁻³
    • HF: 0.13 mg·m⁻³ to ≥10 mg·m⁻³
• Interferences
  • HF can react with co‑sampled particulate matter on the pre-filter, leading to possible positive bias; users must consider this when interpreting results.
• Quality assurance
  • Includes requirements for calibration, blanks, analytical recovery, expression of results and method performance evaluation.

Practical applications and users

• Industrial hygienists and occupational safety professionals conducting air monitoring for fluoride exposures.
• Analytical laboratories performing workplace aerosol analysis by ion chromatography.
• Regulatory and health & safety agencies assessing compliance with occupational exposure limits.
• Industries using or producing HF and fluorides (e.g., glass etching, aluminum production, semiconductor manufacturing).

Related standards

• ISO 21438 parts 1 & 2 (other inorganic acids)
• ISO 7708 (particle size fraction definitions for inhalable sampling)
• Normative references cited: ISO 1042, ISO 3585, ISO 8655 series, EN 13205

This standard provides a reproducible, analytical framework for HF and soluble particulate fluoride monitoring, enabling consistent occupational exposure assessment and control.