The development of the use of fumigants for eliminating decay in timber and roundwood in North America is reviewed. Initial experiments on oak wilt identified volatile chemicals which eradicated decay in roundwood. Subsequently, extensive experimentation on Douglas-fir poles in service showed that treatment with chloropicrin eliminated internal decay for more than ten years. Vorlex was also quite effective, but Vapam appeared to be much less effective, with decay fungi becoming re-established within ten years of treatment. Studies on other wood species indicated that fumigation could be successfully used to treat resistant species such as western red cedar. Fumigation of glulaminated beams and large timbers with chloropicrin, showed that internal decay could also be eliminated in these products, although wrapping the beam in polyethylene was beneficial for optimization of the treatment. Bioassay techniques have been reported for successful monitoring of fumigant vapor concentrations in treated poles.

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