This part of EN 20 specifies a method for the determination of the protective effectiveness or the toxic values of a wood preservative against infestation by Lyctus brunneus (Stephens) in wood which has been treated previously by full impregnation. This method is applicable to: - water-insoluble chemicals which are being studied as acitve insecticides, or - organic formulations, as supplied or as prepared in the laboratory by dilution of concentrates.