From environmental as well as from performance point of view it is of interest to know how much of the preservatives in treated wood that is leached out or evaporated from the wood during service. Many laboratory studies are carried out on leaching from small samples in distilled water or water with different pH. These studies give a good picture of the relative leaching from wood treated with different preservatives, but the results are only true for the actual conditions and not representative for treated wood in service. In many reports on studies concerning treated wood in service the remaining preservatives are analysed, mainly to get to know if the remaining amount of preservatives can prevent the wood from biological attack. Seldom is the initial preservative retention known and therefore the leached amount is not known. To get more facts a questionnaire on leaching during service was sent out to all IRG-members in 1991. 29 answers were received, most of them in form published documents but also information from some unpublished studies. Many of the answers concern results from analyses of field test stakes and very few results from analyses of treated timber in constructions. In some cases laboratory studies of leaching are reported in the same documents. Several documents report only on laboratory experiments. All relevant results are put together in Table 1. Reports only referring to laboratory studies are not included. The reports in Table 1 are in the same order as they were received. In Table 2 all results concerning CCA are put together. These results give a good picture of the difficulties to draw conclusions on leaching during service.

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