In the United States, utility poles are marked with information concerning the manufacturer, pole height, ANSI strength class, wood species, original preservative, and year manufactured (vintage) in accordance with ANSI standard O5.1.2008; this is called branding, as it is usually burned into the surface. Although the position of the brand is determined by ANSI specification, it is essentially just below “eye level” after installation. A general rule of thumb for understanding a pole’s brand is the manufacturer’s name or logo at the top with a 2-digit date beneath (sometimes preceded by a month).
Below the date is a 2-character wood species abbreviation and 1 to 3 character preservative. Some wood species may be: “SP” for southern pine, “WC” for western cedar, and “DF” for Douglas fir; common preservative abbreviations are “C” for creosote, “P” for pentachlorophenol, and “SK” for chromated copper arsenate (originally referred to Salts type K). The next line of the brand is usually the pole’s ANSI Class, used to determine maximum load; this number ranges from 10 to H6 with a smaller number meaning higher strength. The pole’s height (from butt to top) in 5 foot increments is usually to the right of the class separated by a hyphen, although it is not uncommon for older brands to have the height on a separate line. The pole brand is sometimes an aluminum tag nailed in place.
Most utility poles are made of wood, pressure-treated with some type of preservative for protection against rot, fungi and insects. Southern yellow pine is the most widely used species in the United States; however, many species of long straight trees are used to make utility poles, including Douglas-fir, Jack pine, lodgepole pine, western red cedar and Pacific silver fir. Traditionally the preservative used was creosote, but due to environmental concerns, alternatives such as pentachlorophenol, copper naphthenate and borates are becoming widespread in the U.S. For over 100 years, the American Wood Protection Association (AWPA) has developed the standards for preserving wood utility poles. Despite the preservatives, wood poles decay and have a life of approximately 25 to 50 years depending on climate and soil conditions, therefore requiring regular inspection and remedial preservative treatments.
In the above photo, the pole is a 55 ft. class 2.