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woman-worldDevelopment of International Standards

Through its participation in the development of legal metrology standards NIST works to consider the interest of all stakeholders to avoid conflicts with related hydrogen standards developed by national and international standards and codes developing organizations.

Currently, there are two international legal metrology standards which address commercial hydrogen measurement.

R 81
"Dynamic Measuring Devices and Systems for Cryogenic Liquids" (1998)

R 81 Status: R 81 Status: NIST OWM is Secretariat for the International Organization of Legal Metrology (OIML) Recommendation 81 (R 81) and has responsibility for initiating work and ensuring that the standard progresses according to practices established by OIML.

The Secretariat is compiling comments from TC 8/SC 6 on the first working drafts of Part 1 and Part 2 (2013). These comments will be incorporated, where possible, into a first committee draft being readied for distribution and review by national and international work groups in late January 2016.

This draft model regulation includes the metrological and technical requirements and metrological controls and performance tests that apply to measuring devices and systems used for the dynamic measurement of cryogenic liquids in stationary, vehicle mounted, and vehicle refueling applications.

R 139
"Compressed Gaseous Fuel Measuring Systems for Vehicles" (2007)

R 139 is the OIML model regulation for equipment used to deliver compressed gases (natural gas, hydrogen, biogas, etc.) as fuel into motor and fuel cell vehicles, small boats, and aircraft. This document corresponds to the legal metrology requirements in NIST Handbook 44 Section 3.39 Hydrogen Gas-Measuring Devices – Tentative Code.

International Organization of Legal Metrology (OIML) Recommendation (R) 139, Part 1: Metrological and technical requirements (2014), Part 2: Metrological controls and performance tests (2014), and Part 3: Report format for type evaluation (2015) are available on the OIML website at:


For copies of the latest drafts of R 81 please contact For the latest draft of R 139, click here:
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