ISO 6145-7:2018/Amd 1:2026

• Status: Published
• Publication Date: 27-Sep-2026
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: ISO/TC 158 - Analysis of gases
• Drafting Committee: ISO/TC 158/WG 5 - Static and dynamic volumetric methods
• Current Stage: 6060 - International Standard published
• Start Date: 28-Sep-2026
• Due Date: 23-Oct-2026
• Completion Date: 28-Sep-2026

• Consolidates: EN ISO 6145-7:2018/A1:2026 - Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 7: Thermal mass-flow controllers - Amendment 1: Correction of Formula C.4 (ISO 6145-7:2018/Amd 1:2026)
• Effective Date: 12-Feb-2026
• Consolidates: ISO 3104:2023 - Petroleum products — Transparent and opaque liquids — Determination of kinematic viscosity and calculation of dynamic viscosity
• Effective Date: 10-May-2025
• Amends: ISO 6145-7:2018 - Gas analysis — Preparation of calibration gas mixtures using dynamic methods — Part 7: Thermal mass-flow controllers
• Effective Date: 26-Apr-2025

ISO 6145-7:2018/Amd.1:2026 is an amendment from ISO for Part 7 of the ISO 6145 series on gas analysis. It corrects Formula C.4 and related text for preparing calibration gas mixtures using dynamic methods with thermal mass-flow controllers. For readers who calculate or check uncertainty in calibration gas preparation, this document is about getting the referenced formulae and headings consistent with the intended method.

What does ISO 6145-7:2018/Amd.1:2026 specify?

ISO 6145-7:2018/Amd.1:2026 is a correction to the 2018 edition of ISO 6145-7. It does not add a new preparation method - it updates specific text and formulae in the existing material on thermal mass-flow controllers.

The amendment targets three places in the document:

• the paragraph after Figure 3
• the titles of C.1 and C.2
• Formula C.4 and the formulae that follow it

In practice, that means users should read the amended wording and equations when working with the uncertainty calculation in the affected section.

What are the key requirements of ISO 6145-7:2018/Amd.1:2026?

ISO 6145-7:2018/Amd.1:2026 corrects how the affected uncertainty information is stated and calculated in the annex C material. The practical effect is on anyone using the document to prepare or verify calibration gas mixtures with thermal mass-flow controllers.

Corrected percentage notation after Figure 3

The paragraph following Figure 3 replaces the written forms “±10 %” and “±9 %” with “10 %” and “9 %”. That matters because the sign and the value have to match the intended interpretation in the technical text.

Corrected subclause titles in C.1 and C.2

The titles of C.1 and C.2 are corrected so that the ϕA symbol is used consistently. C.1 is for the relative standard uncertainty of ϕA in the case of nominally pure gases, and C.2 is for the relative standard uncertainty of ϕA when diluting a gas mixture. This tells the reader which uncertainty treatment applies to which preparation case.

Corrected Formula C.4 and the following formulae

Formula C.4 and the formulae that follow it are replaced. The amendment states that the expressions are obtained by differentiating Formula C.3 and then substituting the result into Formula C.4 before dividing by ϕA. In practice, this is the calculation pathway used to obtain the relative standard uncertainty of ϕA, so the correction affects anyone performing that uncertainty calculation.

Consequences for users

The corrected text is important for calibration gas mixture preparation because it affects how users document and calculate uncertainty. If a laboratory or supplier uses the thermal mass-flow-controller method, it should apply the amended wording and equations when checking its calculations and technical files.

What terms does ISO 6145-7:2018/Amd.1:2026 define?

• Calibration gas mixtures - Gas mixtures prepared for calibration work, where the composition has to be controlled and documented.
• Dynamic methods - Preparation methods that use controlled gas flow during mixing rather than static preparation.
• Thermal mass-flow controllers - Devices used to control gas flow in the preparation system.
• Relative standard uncertainty - The uncertainty expressed relative to the quantity being evaluated, which is the form used in the corrected Annex C calculation.
• Nominally pure gases - Gases treated as pure for the purpose of the C.1 uncertainty treatment.
• Diluting a gas mixture - The preparation case covered by C.2, where an existing gas mixture is diluted to the desired composition.
• ϕA - The quantity whose relative standard uncertainty is calculated in the corrected annex C text.

Who uses ISO 6145-7:2018/Amd.1:2026?

ISO 6145-7:2018/Amd.1:2026 is used by laboratories, gas mixture producers, calibration specialists, and quality staff who work with calibration gas mixtures made by dynamic methods. It is also relevant to engineers and buyers selecting or validating thermal mass-flow-controller-based preparation equipment.

In practice, these users apply the document when:

• preparing calibration gas mixtures
• checking uncertainty calculations
• writing technical procedures
• reviewing method documentation
• comparing equipment or service offers against the same method basis

What changed in ISO 6145-7:2018/Amd.1:2026 from the previous edition?

ISO 6145-7:2018/Amd.1:2026 is an amendment to ISO 6145-7:2018. The changes stated in the document are:

• correction of the paragraph after Figure 3
• correction of the C.1 and C.2 titles
• replacement of Formula C.4 and the following formulae

What does the ISO 6145-7:2018/Amd.1:2026 document contain?

The document contains the ISO foreword and the amendment instructions that replace specific text in the base part. The technical content focuses on the corrected paragraph after Figure 3 and the corrected annex C formula material.

It also includes the revised wording that supports the uncertainty calculation for ϕA. For users, the important part is not a new process description but the corrected calculation and labeling needed to use the existing method correctly.

International
Standard
ISO 6145-7
Third edition
Gas analysis — Preparation of
2018-12
calibration gas mixtures using
dynamic methods —
AMENDMENT 1
2026-09
Part 7:
Thermal mass-flow controllers
AMENDMENT 1: Correction of
Formula C.4
Analyse des gaz — Préparation des mélanges de gaz pour
étalonnage à l'aide de méthodes dynamiques —
Partie 7: Régulateurs thermiques de débit massique
AMENDEMENT 1: Correction de la Formule C.4
Reference number
ISO 6145-7:2018/Amd.1:2026(en) © ISO 2026

ISO 6145-7:2018/Amd.1:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
ISO 6145-7:2018/Amd.1:2026(en)
Foreword
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Norme
internationale
ISO 6145-7
Troisième édition
Analyse des gaz — Préparation des
2018-12
mélanges de gaz pour étalonnage à
l'aide de méthodes dynamiques —
AMENDEMENT 1
2026-09
Partie 7:
Régulateurs thermiques de débit
massique
AMENDEMENT 1: Correction de la
Formule C.4
Gas analysis — Preparation of calibration gas mixtures using
dynamic methods —
Part 7: Thermal mass-flow controllers
AMENDMENT 1: Correction of Formula C.4
Numéro de référence
ISO 6145-7:2018/Amd.1:2026(fr) © ISO 2026

ISO 6145-7:2018/Amd.1:2026(fr)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2026
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être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
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Publié en Suisse
ii
ISO 6145-7:2018/Amd.1:2026(fr)
Avant-propos
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