Overview
EN ISO 6145-10:2008 (ISO 6145-10:2002) - Gas analysis: Preparation of calibration gas mixtures using dynamic volumetric methods - Part 10: Permeation method.
This standard defines a dynamic permeation technique for producing very low concentration calibration gas mixtures (component mole fractions ≈ 10−9 to 10−6). It explains apparatus, procedures, measurement principles and uncertainty estimation. The method can achieve a relative expanded uncertainty of about 2.5 % of the component mole fraction.
Key topics and technical requirements
- Permeation principle: A calibration component permeates through a membrane from a temperature-controlled tube into a carrier gas; mixture concentration is determined from the permeation rate and carrier-gas flow.
- Concentration range: Target mole fractions between 10−9 and 10−6 - levels difficult to store stably in cylinders, so on-site generation is recommended.
- Uncertainty: The method supports an achievable relative expanded uncertainty of ~2.5 %; the standard includes procedures for estimating uncertainty (mass-loss determination, flow measurement, etc.).
- Apparatus modes:
- Periodic-weighing mode: permeation tube removed periodically and weighed.
- Continuous-weighing mode: permeation tube weighed continuously on a microbalance.
- Materials and design:
- Use chemically inert, low-adsorption materials (glass housings preferred where possible).
- Select permeation membranes (e.g., PTFE, polyethylene, polypropylene, FEP) compatible with the permeant and temperature.
- Seal and junction quality to prevent leaks and adsorption artefacts.
- Measurement controls:
- Temperature-controlled enclosure for stable permeation rates.
- Accurate carrier-gas flow control and measurement (mass flow controllers/meters); if carrier flow is measured as mass-flow the technique becomes a dynamic-gravimetric method providing mole fractions.
- Purity verification of carrier gas (recommended techniques: GC and/or FTIR).
- Reagents: High-purity permeant chemicals; if impurities exist their effects must be known and accounted for.
Applications and users
- Calibration gas generation for environmental monitoring, air quality labs, emissions testing, and analytical instrument calibration (e.g., gas analysers sensitive to SO2, NO2, benzene).
- Useful where ultra-low, short-lived or unstable gas mixtures are needed and must be prepared immediately before use and delivered by the shortest path to the analyser.
- Typical users: calibration laboratories, instrument manufacturers, regulatory agencies, and research institutions.
Related standards
- ISO 6145-1 (Methods of calibration) and other parts of ISO 6145 covering pumps, injection methods, capillaries, critical orifices, thermal mass-flow controllers, saturation method, etc. EN ISO 6145-10:2008 is the CEN adoption of ISO 6145-10:2002.
Keywords: EN ISO 6145-10:2008, ISO 6145-10, permeation method, calibration gas mixtures, gas analysis, permeation tubes, carrier gas, mole fraction, permeation membrane, dynamic volumetric methods, calibration uncertainty.
