BS ISO 6142-2:2024
Gas analysis. Preparation of calibration gas mixtures - Gravimetric method for Class II mixtures

Standard No.

BS ISO 6142-2:2024

Release Date

2024

Published By

British Standards Institution (BSI)  GB  /  BSI

Latest

BS ISO 6142-2:2024

Introduction

Analysis of the core content of the standard

ISO 6142-2:2024, as the second part of the ISO 6142 series of standards, specifically regulates the static gravimetric preparation of Class II calibration gas mixtures.

Key difference features:

• Class II mixtures can be produced in batches
• Use common uncertainty instead of individual verification
• Periodic verification is allowed instead of bottle-by-bottle verification

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Technical Framework Comparison

Technical Dimensions	Class I mixtures (ISO 6142-1)	Class II mixtures (ISO 6142-2)
Production method	Single bottle independent preparation	Support batch production
Verification requirements	Mandatory verification for each bottle	Category-based periodic verification
Uncertainty calculation	Individual uncertainty	General uncertainty model
Applicable concentration range	≥1μmol/mol	≥100μmol/mol

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Uncertainty calculation model

The standard proposes two uncertainty assessment methods:

1. Individual production mode:

   Using formula:
   u_c(y_k) = √[u(y_k,prep)² + u(y_k,ver)² + (y_k,prep-y_k,ver)² + u(v)²]

2. Batch production mode:

   Add the bottle-to-bottle uniformity component:
   u_c(y_k) = √[u(y_k,prep)² + u(y_k,ver)² + (y_k,prep-y_k,ver)² + s_bb²]

Where s_bb is obtained through ANOVA variance analysis, for typical values, see standard Appendix B example:

• CO: 0.107%
• CO₂: 0.092%
• C₃H₈: 0.081%

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Implementation Recommendations

Equipment Selection

It is recommended to use a symmetrical filling manifold with a high-resolution balance (0.1mg level) to ensure:

• Connecting pipes of equal length and diameter
• Filling pressure ≥150bar
• Standardization of gas cylinder pretreatment

Validation cycle management

The standard requires at least 12 months:

1. Raw material change assessment
2. Production process change verification
3. Analytical equipment calibration confirmation

Document control

Key records that need to be retained for more than three years:

• Verification of original data
• Uncertainty calculation process
• Category classification basis

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Typical application cases

Automobile emission detection gas:

According to the example in Appendix C of the standard, a unified uncertainty can be used for a multi-component mixed gas (CO/CO₂/C₃H₈/N₂):

Component	Concentration range	Urel
CH4	>25cmol/mol	0.5%
CH4	0.05-1cmol/mol	1.5%

The uncertainty of low concentration components can be optimized by staged dilution of the premix.

BS ISO 6142-2:2024 Referenced Document

• ISO 6141 Gas analysis — Contents of certificates for calibration gas mixtures — Amendment 1: Cross reference list to ISO Guide 31:2015 and ISO/IEC 17025:2017
• ISO 6142-1:2015 Gas analysis - Preparation of calibration gas mixtures - Part 1: Gravimetric method for Class I mixtures
• ISO 7504 Gas analysis - Vocabulary

BS ISO 6142-2:2024 history

• 2024 BS ISO 6142-2:2024 Gas analysis. Preparation of calibration gas mixtures - Gravimetric method for Class II mixtures

Standard and Specification