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ABSTRACT
One purpose of ANSI/ASHRAE Standard 34, Designation and Safety Classification of Refrigerants, has been to provide safety classifications for refrigerants that reflect their flammability potential.
This paper provides a description and brief history of refrigerant flammability safety classification systems, a summary of a literature survey of flammability test data for single-compound refrigerants and refrigerant blends, and also presents new flammability test results on the lower flammability limits (LFLs) of refrigerants and refrigerant blends containingflammable components that are currently ASHRAE designated and classified. The results presented were determined under ASHRAE Research Project 1073. The new LFL data are relative to new test method requirements set forth in proposed Addendum p to ANSI/ASHRAE Standard 34-1992 (34p-1992).1 With the results presented here, a self-consistent database of flammability results now exists to support ASHRAE flammability safety classifications under 34p-92.
INTRODUCTION
Since 1992, more than 30 new refrigerants have been added to or assigned safety classifications in Standard 34 due to the movement of industry away from the use of ozonedepleting substances as refrigerants. It quickly became apparent that major revisions to ASHRAE safety classification schemes were needed to implement a self-consistent and technically sound basis for classifying this large number of new
1. Later editions of Standard 34 were published in 1997 and 2001, but the addendum discussed here is still under consideration by SSPC34.
refrigerants. The motivation for introducing new methods and criteria for classification was due to a great degree on a number of key factors and issues that had surfaced at the time within ASHRAE SSPC 34 and SSPC 15: inconsistency in toxicity criteria applied in the determination of "quantity of refrigerant per occupied space" and lack of toxicity expertise in Standard 15; inconsistency in LFL data test conditions and parameters for refrigerants in Tables 1 and 2 of Standard 34; differences in flammability classification systems used by ASHRAE 34 and UL 2182 and the need to establish/harmonize a "national" refrigerant safety classification standard; and a need to classify a large number of new refrigerants with unfamiliar characteristics, many of which were fractionating zeotropes whose toxicity and flammability classifications had to account for their compositional change in properties during transport, storage, and use in equipment.
Two major recommended changes to ASHRAE Standard 34...