209 Refrigerants ranked by Partial Order Theory Guillermo Restrepo 1 , 2 , Monika Weckert 1 , Rainer Brüggemann 3 , Silke Gerstmann 1 , Hartmut Frank 1 Abstract Forty refrigerants used in the past, used presently, and some proposed substitutes, were studied in respect to their ozone depletion potential, global warming potential, and atmospheric life times. They were ranked using the Hasse diagram technique, a mathematical method which permits to draw diagrams representing order relations among chemicals. The refrigerants were divided into 13 chemical classes (subsets) of which the most prominent ones are the chlorofluoro- carbons (CFC), hydrofluorocarbons, hydrochlorofluorocarbons and hydrofluoroethers. Order relations among these subsets were calculated applying dominance and separability degrees. The dominance degree is a measure indicating the extent to which descriptors of members of one subset are higher than those of members of other subsets; the separability degree is a measure for the incomparability or lack of order relations between elements of two subsets. By application of these measures to the 13 chemical subsets it was found that more than half of the order relations among them are com- plete dominances; this means a high degree of comparability among subsets permitting to find the ones most problematic in environmental terms. This is the case for the CFC and for some of the hydrofluoroethers. 1. Introduction Chlorofluorocarbons (CFC) have been used as refrigerants (Stemmler et al., 2004) but due to environmental problems, i.e. their high ozone depletion potential (ODP), their global warming potential (GWP) and their long atmospheric life times (ALT) (Molina and Rowland 1974, Rowland 1994, UNEP 1987, 1998, UNFCCC 1997) industry looked for substitutes; hydrochlorofluorocarbons (HCFC) and hydrofluorocar- bons (HFC) became the first-generation alternatives (Haymann and Derwent, 1997). However, the latter still are not fully satisfactory; therefore, the search continues (Stemmler et al., 2004; UNFCCC 1997). Some of the newly proposed substances are chlorine-free fluorinated ethers, hydrocarbons (HC), alcohols, amines, and mixtures thereof (Sekiyaa and Misaki, 2000; Swaminathan, 2005a, b; Bivens, 1998). Prior to commencement of large-scale production, industry and regulatory agencies assess potential substitutes in respect ODP, GWP, ALT, toxicity, insulating ability, flammability, physical and chemical stability, solu- bility, cost, and other aspects of technical applicability (Sumantran et al., 1999; Swaminathan and Visco, 2005a, b;WMO 1991, 1992, 1995). Normally an assessment implies that a decision is made based upon ranking of the substances under consideration (Lerche et al., 2002; Brüggemann, 1999); for this purpose, the Hasse diagram technique (HDT) (Brüggemann et al., 1993, 1994, 2001) is one of the most general and least subjective procedures (Lerche et al., 2002). In the present work, the HDT is applied to a set of 40 refrigerants taking ODP, GWP and ALT into consideration. After ranking, the refrigerants are divided into 13 subsets, and their order relations are studied by calculation of the two measures of comparability and incomparability, the domi- nance and the separability degrees. 1 Environmental Chemistry and Ecotoxicology, University Bayreuth, Germany email: guillermo.restrepo@uni-bayreuth.de, Internet: www.uni-bayreuth.de/departments/umweltchemie/ 2 Laboratorio de Química Teórica, Universidad de Pamplona, Colombia 3 Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany EnviroInfo 2007 (Warschau) Environmental Informatics and Systems Research Copyright © Shaker Verlag, Aachen 2007. ISBN: 978-3-8322-6397-3