Utility poles treated with DCOI are the most common utility poles, accounting for almost 50% of the total market. Like other wood preservatives, DCOI is a pesticide, which acts against wood-destroying fungi and insects.
DCOI also provides protection against a variety of insects such as termites and powder post beetles. In stake tests and actual use, DCOI has been shown to preserve wood eight to twenty times beyond its normal service life expectancy.
DCOI is carried into the pole in a petroleum oil solution. When properly applied, DCOI remains in treated wood products for many years. However, when present in low concentrations, DCOI is degradable by sunlight and certain bacteria. Thus, over time, treated wood surfaces become relatively free of DCOI while the preservative continues to work below the surface.