ISO 6142-2:2024

Overview

ISO 6142-2:2024 - Gas analysis - Preparation of calibration gas mixtures - Part 2: Gravimetric method for Class II mixtures provides standardized guidance for the static gravimetric preparation of Class II calibration gas mixtures and for calculating the measurement uncertainty of each component’s amount fraction. It extends the principles in ISO 6142-1 to cover batch production, generic uncertainties for categories of mixtures, and validation processes for mixtures that are not individually verified.

Key topics and requirements

• Scope and applicability
  • Applies to gaseous or fully vaporized components (introduced as gas or liquid).
  • Covers both binary and multi‑component non‑reactive mixtures with amount fractions ≥ 100 µmol/mol.
  • Excludes reactive components or compounds that react with contaminants (e.g., water vapour, oxygen) or adsorb/absorb on cylinder surfaces.
• Gravimetric preparation principles
  • Uses the gravimetric approach of ISO 6142-1 for individual production and adapts it for Class II mixtures.
  • Describes procedures for both individual and batch filling.
• Validation and generic uncertainty
  • Defines a generic uncertainty for a category of mixtures (representative uncertainty applied to multiple cylinders rather than calculated per cylinder).
  • Recommends preparing and verifying preferably n = 10 (minimum 6) gravimetric mixtures to estimate generic uncertainty.
  • Includes an additional uncertainty term from the validation process and explains how to combine uncertainty contributions (amending ISO 6142-1 formulas).
• Batch production and statistical control
  • Provides methods for batch filling and producing multiple mixtures in a single process.
  • Uses one‑way ANOVA to determine between‑bottle variance (sbb) and incorporate it into the uncertainty budget.
  • Requires statistical process control and periodic reconfirmation of the generic uncertainty.
• Quality assurance
  • Addresses requirements for repeated verifications, document control, and preparation of certificates (see Clause 10).
• Related normative references
  • ISO 6142-1 (Class I methods), ISO 6141 (certificate content), ISO 7504 (vocabulary).

Applications and users

ISO 6142-2:2024 is intended for:

• Calibration gas manufacturers and suppliers preparing Class II calibration gas mixtures.
• Metrology institutes, analytical laboratories, and environmental monitoring organizations needing standardized uncertainty evaluation.
• Quality managers and accreditation bodies assessing production processes, validation methods, and certificate content.
• Industries that require routine, high‑throughput production of calibration gases (e.g., emissions testing, process control, gas detection calibration).

Practical benefits include streamlined batch production, representative uncertainty budgeting across mixture categories, and harmonized validation procedures that support accreditation and traceable gas calibration.

Related standards

• ISO 6142-1:2015 - Gravimetric method for Class I mixtures (individual verification).
• ISO 6141 - Contents of certificates for calibration gas mixtures.
• ISO 7504 - Gas analysis vocabulary.
• ISO Guide 35 - Guidance cited for ANOVA and homogeneity studies.