ISO 21438-2:2024

Overview

ISO 21438-2:2024 is an international standard developed by the International Organization for Standardization (ISO) that specifies a reliable method for determining the time-weighted average (TWA) mass concentrations of volatile inorganic acids in workplace air. Specifically, it covers the analysis of hydrogen chloride (HCl) gas and mist, hydrogen bromide (HBr) vapor and mist, and nitric acid (HNO₃) vapor and mist. Hydrofluoric acid is explicitly excluded from the scope of this document. The method utilizes alkali-impregnated quartz fibre filters for sample collection and ion chromatography for quantitative analysis. This standard is essential for occupational health professionals, analytical laboratories, and industries using these acids, offering a validated approach for assessing worker exposure in compliance with regulatory requirements.

Key Topics

• Workplace air monitoring: The standard details procedures for sampling and analysis of volatile acids to assess occupational exposure.
• Ion chromatography method: Specifies how inorganic acids are collected and accurately quantified, ensuring reliable exposure assessment.
• Sampling techniques: Addresses personal sampling of inhalable fractions (as per ISO 7708), static (area) sampling, and proper handling for both gases and mists.
• Quality control and assurance: Outlines steps for calibration, use of certified reference materials, preparation of calibration solutions, and implementation of blanks to ensure data integrity.
• Health and safety: Highlights the importance of valid exposure assessment in environments where hydrochloric acid, hydrobromic acid, and nitric acid are present, supporting efforts to control risks and meet occupational exposure limits.

Applications

ISO 21438-2:2024 provides practical value in several areas, including:

• Occupational hygiene monitoring: Enables industrial hygienists and safety officers to evaluate employee exposure to hazardous volatile acids in manufacturing, chemical processing, mining, and laboratories.
• Compliance with health standards: Facilitates organisations in meeting local and international workplace air quality regulations by providing a standardized and recognized measurement procedure.
• Analytical laboratory practices: Serves as a reference method for accredited laboratories offering workplace atmosphere monitoring, ensuring accuracy and repeatability in measurements of HCl, HBr, and HNO₃.
• Risk assessment and mitigation: Supports companies in identifying exposure hotspots, informing engineering controls, and evaluating the effectiveness of personal protective equipment and ventilation systems.
• Regulatory reporting: Assists employers in providing evidence-based documentation for regulatory authorities, workers, and stakeholders regarding airborne acid concentrations.

Related Standards

To ensure comprehensive workplace air analysis and adherence to best practices, the following related standards are often referenced alongside ISO 21438-2:2024:

• ISO 7708: Defines particle size fractions relevant for health-related sampling in air quality monitoring.
• ISO 20581: General requirements for procedures measuring chemical agents in workplace air.
• EN 13205: Assessment of sampler performance for airborne particle concentration measurement.
• ISO 21832: Requirements for evaluating measuring procedures for metals and metalloids in airborne particles.
• ISO 18158: Provides workplace air terminology to ensure consistency across related standards.
• ISO 3696: Sets out water requirements for laboratory analytical use, crucial for minimizing contamination.
• ISO 13137: Describes requirements for personal sampling pumps used in air sampling.

Adopting ISO 21438-2:2024 as part of workplace air monitoring programs ensures scientifically robust, internationally recognized practices for safeguarding worker health in settings where exposure to volatile inorganic acids is a concern.