Fumigants are designed to help protect in-service utility poles against strength loss caused by internal decay and insect attack. They produce vapors that move within the pole both vertically and horizontally from the application holes, helping to eliminate wood-destroying fungi. They are ideal for protecting heartwood and inner regions of poles. Fumigant applications can help control incipient decay and help to prevent future fungal attack. They can be especially helpful when treating Western species (fir and cedar). Western species are prone to internal decay because they are largely heartwood which is difficult to penetrate and treat.
Fumigants are applied into holes drilled in the pole. After application, the fumigants begin to volatize and migrate through the solid wood several feet from the point of application.