The International Institute of Ammonia Refrigeration (IIAR) released a 128-page safety standard for CO2 closed-circuit systems on March 1 on its website, and is seeking comments on the standard during an initial public review period that ends on April 15.

Interested parties can access a draft of the standard and submit comments at

The CO2 standard represents IIAR’s latest venture outside of its traditional ammonia focus as it broadens its missions to include all natural refrigerants. It was developed for both commercial and industrial refrigeration applications.

IIAR identified a “need to provide this resource to the industry at this time,” said John Collins, industrial sales manager for Zero Zone and chairman of the IIAR’s CO2 Task Group.

He spoke about the standard Monday at a session on commercial standards at the 2019 IIAR Natural Refrigeration Conference & Expo, being held in Phoenix March 4-6.

The standard is “limited to the minimum requirements for providing safe [CO2] systems, noted Collins, adding that it is not reflective of best practices. It is also intended to serve as a basis for model code compliance.

The standard covers all phases of CO2 system’s lifecycle, from design, installation and start-up to inspection, testing and maintenance. It encompasses the CO2 portion of a cascade system, systems using CO2 as a secondary fluid, systems operating part- or full-time in the transcritical cycle, and heat pumps.

The standard addresses areas “where our industry has been lacking in clear and consistent guidance,” such as installation and start-up requirements as well as inspection, testing and maintenance, said Collins.

IIAR standards typically go through two or more iterations of public review, said Collins. Following review, the standard is evaluated by a consensus body of stakeholders, voted on by the IIAR Standards Committee and then submitted for approved by the IIAR board and the American National Standards Institute (ANSI), after which it is published.

Publication of the standard “is where things will get interesting,” said Collins. “How the standard is received and used in the coming years is to be determined.”

“The standard is “limited to the minimum requirements for providing safe [CO2] systems.”

John Collins, Zero Zone

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