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Preservative-Treated Wood and Alternative Products in the Forest Service

Summary of Preservative Properties

Table 1 summarizes the properties of the most commonly used preservatives.

Table 1-The properties and uses of common preservatives.
Standardized use Preservative Solvent Characteristics Surface/handling restrictions Color Odor Fastener corrosion
All uses Creosote Oil-type Oily, not for frequent human contact Dark brown Strong, lasting No worse than untreated
Ammoniacal copper zinc arsenate Water Dry, but contains arsenic Brown, possible blue areas Mild, short term Worse than untreated wood
Chromated copper arsenate Water Dry, but uses are restricted by the EPA* Greenish brown, weathers to gray None Similar to untreated wood
All uses (except in seawater) Pentachlorophenol in heavy oil No. 2 fuel oil Oily, not for frequent human contact Dark brown Strong, lasting No worse than untreated wood
Copper naphthenate No. 2 fuel oil Oily, not for frequent human contact Green, weathers to brownish gray Strong, lasting No worse than untreated wood
Alkaline copper quat Water Dry, okay for human contact Greenish brown, weathers to gray Mild, short term Worse than untreated wood
Copper azole Water Dry, okay for human contact Greenish brown, weathers to gray Mild, short term Worse than untreated wood
Aboveground, fully exposed Pentachlorophenol in light oil Mineral spirits Dry, okay for human contact if coated Light brown, weathers to gray Mild, short term No worse than untreated wood
Oxine copper Mineral spirits Dry, okay for human contact Greenish brown, weathers to gray Mild, short term No worse than untreated wood
Aboveground, partially protected (such as millwork) IPBC + permethrin Mineral spirits Dry, okay for human contact Colorless Mild, short term No worse than untreated wood
Indoors (usually for insect protection) Borates Water Dry, okay for human contact Colorless, blue dye often added None No worse than treated wood
*A few uses of chromated copper arsenate are still allowed for treatment of sawn products less than 5 inches thick (12.7 centimeters, such as dimension lumber). Pilings, poles, large timbers, and plywood are still allowed for highway construction.—Courtesy of USDA Forest Service, Forest Products Laboratory