New European standards for the preservative pre-treatment of timber require the results of the treatment process to be specified and subsequently verified by examination of the treated timber for penetration and retention of the preservative. For penetration, the standards are restrictive in that there are only a limited number of options available to the specifier. Thus for ground contact service, the appropriate option is full sapwood penetration. This paper describes a study in which the ability to meet a results specification for full sapwood penetration of Douglas fir fence posts with CCA was examined by treating 500 fence posts using a vacuum/high pressure process. When all treated fence posts were examined it was demonstrated that full sapwood penetration was not always possible. However, by applying different sampling systems linked to "acceptable quality levels" it was possible to develop an inspection scheme that ensured that batches of fence posts treated to the best achievable level were accepted under a full sapwood penetration specification. However, it was demonstrated that such a system would also allow some sub-standard batches to be accepted.

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