While field testing of wood protective formulations remains probably the best method to find out the effective preservative concentration, the use of chrome-copper arsenate (CCA) as reference becomes debatable due to environmental and legislative reasons. This emerges from the European standardization bodies who have discussed reference alternatives that can omit the use of CCA. The present debate article suggests one possible approach to cope with the problem. CCA has served in the tests fields of the Nordic countries for more than 50 years and thus, offers a solid database for modelling of its behaviour and service life in in-ground conditions. Based on data from the field of Simlångsdalen (Sweden), this paper outlines a simple but reliable model that can substitute the use of CCA. Seventeen tests were included into the model; some extremes, i.e. very short or long test durations were discarded. Statistical analysis shows that both logarithmic and linear regressions can describe the decay index in a similar way. Some applications of the model to real test data that the Technical Group at the Nordic Wood Protection Council works with have been compared to the standard method based on the European standard EN 599-1. Results demonstrated that the model generates similar data of formulation concentrations compared to the standard method. It is suggested that identical models, based on data from the other Nordic fields, could be developed and applied. The proposed method demands a wide discussion between the testing and standardization bodies for further practical implementation.

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