ISO 6145-1:2019

Overview

ISO 6145-1:2019 - Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 1: General aspects provides a concise, authoritative overview of dynamic techniques used to prepare calibration gas mixtures. The standard explains principles for producing continuous or pseudo-continuous calibration gas flows by combining known mass or volume flow rates from parent gases, and describes how to link these dynamic methods to national measurement standards to establish metrological traceability.

Key topics and requirements

• Scope and applicability: Applies to pure gases, gas mixtures and totally vaporized components that do not chemically react with each other or system surfaces. Storage of prepared mixtures in bags or cylinders is outside the scope.
• Dynamic methods overview: Summarizes principal techniques - piston pumps, continuous (syringe) injection, capillary, critical flow orifices, thermal mass flow controllers, diffusion, saturation, permeation and electrochemical generation - with advantages and limitations for each.
• Flow-rate based preparation: Emphasizes that all dynamic methods rely on accurately measured mass flow rates or volume flow rates; composition is calculated from flow data and parent-gas compositions.
• Calibration and traceability: Describes calibration of each flow element, options for single-point comparison with validated reference gas mixtures, and procedures to link results to national measurement standards.
• Uncertainty and calculations: Includes required expressions and guidance for calculating the composition of prepared calibration gases and evaluating the associated uncertainty (volumetric and gravimetric mixing approaches are considered).
• Quality, verification and documentation: Recommends quality and safety considerations (gas purity, materials compatibility, handling), verification and recalibration criteria, and content expectations for calibration certificates.

Applications and users

ISO 6145-1:2019 is essential for professionals involved in gas analysis, calibration and metrology, including:

• Metrology institutes and national measurement laboratories establishing traceable calibration chains
• Manufacturers and users of gas analysers and continuous monitoring systems
• Calibration service providers preparing on-line or dynamic calibrations
• Environmental monitoring, industrial process control, and laboratory quality assurance teams

This standard helps ensure calibration gas mixtures used for instrument calibration or control meet traceability, accuracy and uncertainty requirements.

Related standards

Normative references and related standards include:

• ISO 6143 (comparison methods for checking calibration gas composition)
• ISO 7504 (gas analysis vocabulary)
• ISO 12963 (comparison methods - one- and two-point calibration)
• ISO 14912 (conversion of gas mixture composition data)
• ISO 19229 (purity analysis and treatment of purity data)

Keywords: ISO 6145-1:2019, calibration gas mixtures, dynamic methods, gas analysis, flow rate calibration, metrological traceability, uncertainty calculation, gas analysers.