What is the most common preservative used on poles?

Pentachlorophenol is the most common preservative used on utility poles due to its effectiveness in protecting against a wide range of wood-destroying organisms, including fungi and insects. This preservative has a long history of use in the wood preservation industry, particularly for outdoor applications where wood is exposed to moisture and potential decay. Its ability to penetrate deeply into the wood fibers ensures a longer-lasting protection against deterioration, making it an ideal choice for structures that need to withstand the elements for extended periods.

In addition to its protective qualities, pentachlorophenol is recognized for its resistance to leaching, which helps maintain its efficacy even in environments with high humidity or rainfall. This makes it particularly suited for utility poles, which must endure various weather conditions while maintaining structural integrity over time.