ASHRAE Journal - November 2014 - 43

TECHNICAL FEATURE

the number of new refrigerants included within ASHRAE
Standard 34 increased, it became difficult for Standard
15 to remain current and the decision was made in the
2007 edition of ASHRAE Standard 15 to completely remove
the safety classifications of refrigerants originating from
Standard 34 and to simply reference Standard 34 for that
safety information. To better serve the users of Standard 15,
the decision was made to co-publish both Standard 15 and
Standard 34 as companion standards.
The 2010 edition of Standard 15 included a number
of changes. One of the more significant changes was
driven by updates to Standard 34 as it transitioned to a
new safety metric in its 2007 edition-refrigerant concentration limit (RCL). The RCL represents a refrigerant
concentration limit, in air, intended to reduce the risks
of acute toxicity, asphyxiation, and flammability hazards
in normally occupied, enclosed spaces. This metric is
determined by Standard 34 for each refrigerant using a
multifactor approach that considers the acute-toxicity
exposure limit (ATEL), oxygen deprivation limit (ODL),
and flammable concentration limit (FCL). In applications where the catastrophic loss of refrigerant would
lead to a concentration in a normally-occupied enclosed
space in excess of the RCL, Standard 15 requires the
refrigerant-containing parts of that system to be located
in a machinery room or outdoors. A number of other
changes were incorporated into the 2010 edition including provisions for systems using carbon dioxide as a
refrigerant.
The 2013 edition of Standard 15 was released in
December last year and the changes reflected from the
2010 edition were relatively minor but include clarification of requirements for machinery room ventilation
systems, securing of refrigerant circuits located outdoors
to prevent unauthorized access, and the removal of obsolete appendices. In January, ASHRAE issued Addendum
a to this most current edition of Standard 15 for "immediate publication" due to the nature of the changes
it addresses. Addendum a modifies and clarifies the
requirements for discharge of pressure-relief devices,
including locations where refrigerant may be safely
discharged in the event of a release. Systems located
outdoors are now specifically addressed and include
an exemption from the Standard 15 ft (4.57 m) height
requirement if specified criteria for the installation are
met. The timeline (Figure 2, Page 40) summarizes the history of this refrigeration safety standard.

Conclusions
Today, ANSI/ASHRAE Standard 15 continues to evolve
and address refrigeration system safety for stationary
systems. Although analog refrigeration safety standards
such as the Canadian standard CSA B52, the international standard ISO 5149, and others have been introduced, ANSI/ASHRAE Standard 15 continues today as a
benchmark for refrigeration system safety in the built
environment. No other refrigeration safety standard has
the legacy of ASHRAE Standard 15, and none other has
protected more people from refrigerant-related hazards
in the built environment. Currently, the Standard 15
committee is in the process of transforming this standard again as it pursues an entire rewrite of the document. The goals of the rewrite are to: enhance usability,
ensure all requirements are clear, unambiguous, and
enforceable, and remove duplication.

References
1. Edwards, H.D. 1934. "The refrigeration safety code - a review
of two decades." Refrigerating Engineering, 28(5):231-240.
2. Reindl, D.T., Jekel, T.B. 2008. "Fundamentals of safety relief
systems." ASHRAE Journal 50(2):22-29.

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ASHRAE Journal - November 2014

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