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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: 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 Committee on International Legal Metrology approved Project 1, a revision of the 1998 version of R 81 to include: (1) new ISO and IEC Standards as recommended in OIML D 11, (2) new developments in hydrogen measurements, (3) revised density equations, and (4) any other remaining relevant standards and national documents. The OIML Technical Committee 8/Subcommittee 6 (TC 8/SC 6) project group will develop this recommendation.

On May 20, 2013, the Secretariat distributed a first working draft (1WD) of R 81 "Dynamic Measuring Devices and Systems for Cryogenic Liquids” to national stakeholders and the TC 8/SC 6 project group for their review and comments by the September 30, 2013 deadline. 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.

The Final Draft Recommendation of OIML R 139 parts 1 and 2 is available on the website: This document combines part 1 (-1): metrological and technical requirements and part 2 (-2): metrological controls and performance tests. OIML R 139-1 and -2 will be forwarded for approval during the 49th Meeting of the International Committee of Legal Metrology (CIML) held November 3-6, 2014 in Auckland, New Zealand.

The first committee (1CD) draft of OIML R 139 part 3 (R 139-3), the associated test report, is posted on the OIML website at: Technical Committee 8/Subcommitte 7Project group 4 has a deadline of August 23, 2014 to review and comment on the 1CD.


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