During experimental work on accelerated fixation of chromium containing preservatives a method has been developed which compares the degree of preservative levels of contamination of simulated preservative fixation in timber with the levels of simulated rainfall. This method uses commercial sized wood sections wetted in a way that simulates actual rainfall and relates the associated run-off contamination to absolute fixation levels. The results show the excellent correlation between fixation level and CCA levels in shower test run-off water. Whilst the test does not set out to determine pollution levels which might be encountered in practice the results highlight the tremendous difference in chemical levels removable from 'fully fixed' timber (i.e. the 99% fixation level) and the amounts of CCA which are removable from freshly treated wood when exposed to rainfall. The test highlights the need to either provide the kind of self contained areas mentioned earlier which are effective in preventing contaminated run-off water from polluting the environment or to use controlled fixation techniques so that unfixed CCA does not come into contact with rainfall.

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