This guideline defines a standardized test apparatus and procedure for experimentally conducting fractionation analyses of refrigerant blends to determine the worst case of fractionation for flammability (WCFF) composition of refrigerant blends or to validate computer simulation programs for fractionation analysis. PURPOSE The purpose of this guideline is to establish test methods and procedures to obtain accurate experimentally determined fractionation (vapor and liquid) compositions of refrigerant blends under simulated isothermal leak events from containers and equipment in storage@ transport@ operation@ and service. A fractionation analysis is undertaken to determine the worst case of fractionation for flammability (WCFF) of a refrigerant blend in order for ASHRAE SSPC 34 to assign flammability safety classifications under criteria established in ANSI/ASHRAE Standard 34. The WCFF@ with respect to flammability and worst case of formulation (WCF) compositions of a refrigerant blend@ are tested for flammability to determine the refrigerant??s lower flame limit@ which is used@ along with the calculated heat of combustion@ in assigning a flammability safety classification for a refrigerant blend.