SIST EN ISO 14912:2025

Overview

EN ISO 14912:2025 - Gas analysis - Conversion of gas mixture composition data (ISO 14912:2025), published by CEN/ISO, specifies internationally harmonized methods to express and convert gas mixture composition. The standard defines the common composition quantities - amount fraction, mass fraction, and volume fraction (and their concentrations) - and gives procedures to convert between these quantities and between different state conditions (pressure and temperature). It applies to homogeneous, stable gas mixtures and requires state conditions outside the condensation region.

Key topics and requirements

• Defined quantities and units: clear definitions, symbols and units for amount, mass and volume fractions and concentrations.
• Conversion methods: procedures to convert the content of a specified component from one quantity to another at the same state conditions.
• State-condition conversion: methods to calculate compositions under one set of pressure and temperature from values given at another set. Conversions can be combined (quantity + state).
• Applicability limits:
  • Volume concentrations/fractions usable only when component(s) are completely gaseous.
  • All state conditions must be well outside the condensation region.
  • Additional restrictions apply when using compression factor approximations with virial coefficients (see Annex A).
• Practical implementation: main procedures for single-component and complete-composition conversions, reference condition conversions, and simple approximations (ideal mixture/ideal gas, ideal mixture of real gases, trace mixtures).
• Input data and uncertainty: guidance on required input (pure-gas molar mass, compression factor, mixing factor), uncertainty estimation and propagation for conversions.
• Supporting material: informative annexes with state assessment (A), summation relations (B), mixture component data and updated molar masses (C), worked examples (D), and computer implementation guidance (E).

Applications and users

EN ISO 14912:2025 is essential for:

• Gas analysis laboratories and metrology institutes performing compositional reporting and uncertainty evaluation.
• Calibration gas producers and suppliers converting certificate data between units and reference conditions.
• Instrument manufacturers and integrators needing consistent input/output composition formats.
• Environmental monitoring, combustion, gas appliance testing, and industrial gas management where conversions between mass, amount and volume bases and between pressures/temperatures are required.

Related standards

• Supersedes EN ISO 14912:2006 (and its corrigenda).
• Works alongside gas analysis and metrology standards (see normative references and bibliography in the standard) and aligns with updated IUPAC atomic mass data and SI revisions (molar mass and gas constant updates noted in the 2025 edition).

Keywords: EN ISO 14912:2025, gas analysis, conversion of gas mixture composition data, amount fraction, mass fraction, volume fraction, compression factor, virial coefficients, gas composition conversion, uncertainty.