NIST logo

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 Status: In December 2012, the Secretariat (the Netherlands) for International Organization of Legal Metrology (OIML) Recommendation 139 (R 139) "Compressed Gaseous Fuel Measuring Systems for Vehicles" distributed the second committee draft (2CD) of the international standard for comment and vote of Technical Committee 8/Subcommittee 7 (TC 8/SC 7) for Project 4. The document 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 2CD of R 139 includes part 1 (-1): metrological and technical requirements and part 2 (-2): metrological controls and performance tests, which will be combined. The last part to be completed is part 3, the test report. Part 3 will be developed after the TC 8/SC 7 reaches a consensus on parts 1 and 2.

In January 2013, NIST OWM distributed the 2CD of OIML R 139-1 and -2 to the OIML R 139 U.S. National Working Group (USNWG) for comment to develop a U.S. position and vote on this latest revision. U.S. comments and yes vote were submitted to the OIML Secretariat on the 2CD for R 139 by the April 5, 2013 OIML deadline.

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

By selecting these links, you will be leaving NIST webspace. We have provided these links to other web sites because they may have information that would be of interest to you. No inferences should be drawn on account of other sites being referenced, or not, from this page. There may be other web sites that are more appropriate for your purpose. NIST does not necessarily endorse the views expressed, or concur with the facts presented on these sites. Further, NIST does not endorse any commercial products that may be mentioned on these sites. Please address comments about this page to
Bookmark and Share