Wood preservation refers to any method or process, or even technique, used to protect wood and extend its service life. Most wood species are susceptible to both biological (biotic) and non-biological (abiotic) factors that cause decay and/or deterioration. Only a limited number of wood species possess natural durability, and even those may not be suitable for all environments. In general, wood benefits from appropriate preservation measures. In addition to structural design considerations, a variety of chemical preservatives and treatment processes — commonly known as timber treatment, lumber treatment, pressure treatment or modification treatment — are used to enhance the durability of wood and wood-based products, including engineered wood. These treatments may involve physical, chemical, thermal, and/or biological methodology aimed at protecting wood from degradation. They increase its resistance to biological agents such as fungi, termites, and insects, as well as non-biotic factors such as ultraviolet radiation (sunlight), moisture and wet-dry cycling, temperature extremes, mechanical wear, exposure to chemicals, and fire or heat. Effective preservation treatments significantly improve the durability, structural integrity, and overall performance of wood in service.
History
As proposed by Richardson, treatment of wood has been practiced for almost as long as the use of wood itself. There are records of wood preservation reaching back to ancient Greece during Alexander the Great's rule, where bridge wood was soaked in olive oil. The Romans protected their ship hulls by brushing the wood with tar. During the Industrial Revolution, wood preservation became a cornerstone of the wood processing industry. Inventors and scientists such as Bethell, Boucherie, Burnett and Kyan made historic developments in wood preservation, with preservative solutions and processes. Commercial pressure treatment began in the latter half of the 19th century with the protection of railroad cross-ties using creosote. Treated wood was used primarily for industrial, agricultural, and utility applications, where it is still used, until its use grew considerably (at least in the United States) in the 1970s, as homeowners began building decks and backyard projects. Innovation in treated timber products continues to this day, with consumers becoming more interested in less toxic materials.
Hazards Wood that has been industrially pressure-treated with approved preservative products poses a limited risk to the public and should be disposed of properly. On December 31, 2003, the U.S. wood treatment industry stopped treating residential lumber with arsenic and chromium (chromated copper arsenate, or CCA). This was a voluntary agreement with the United States Environmental Protection Agency. CCA was replaced by copper-based pesticides, with exceptions for certain industrial uses. CCA may still be used for outdoor products like utility trailer beds and non-residential construction like piers, docks, and agricultural buildings. Industrial wood preservation chemicals are generally not available directly to the public and may require special approval to import or purchase, depending on the product and the jurisdiction where being used. In most countries, industrial wood preservation operations are notifiable industrial activities that require licensing from relevant regulatory authorities such as EPA or equivalent. Reporting and licensing conditions vary widely, depending on the particular chemicals used and the country of use. Although pesticides are used to treat lumber, preserving lumber protects natural resources (in the short term) by enabling wood products to last longer. Previous poor practices in industry have left legacies of contaminated ground and water around wood treatment sites in some cases. However, under currently approved industry practices and regulatory controls, such as implemented in Europe, North America, Australia, New Zealand, Japan and elsewhere, environmental impact of these operations should be minimal. Wood treated with modern preservatives is generally safe to handle, given appropriate handling precautions and personal protection measures. However, treated wood may present certain hazards in some circumstances, such as during combustion or where loose wood dust particles or other fine toxic residues are generated, or where treated wood comes into direct contact with food and agriculture. Preservatives containing copper in the form of microscopic particles have recently been introduced to the market, usually with "micronized" or "micro" trade names and designations such as MCQ or MCA. The manufacturers represent that these products are safe and EPA has registered these products. The American Wood Protection Association (AWPA) recommends that all treated wood be accompanied by a Consumer Information Sheet (CIS), to communicate safe handling and disposal instructions, as well as potential health and environmental hazards of treated wood. Many producers have opted to provide Material Safety Data Sheets (MSDS) instead. Although the practice of distributing MSDS instead of CIS is widespread, there is an ongoing debate regarding the practice and how to best communicate potential hazards and hazard mitigation to the end-user. Neither MSDS nor the newly adopted International Safety Data Sheets (SDS) are required for treated lumber under current U.S. Federal law.
Chemical In general, the chemical preservatives can be classified into three broad categories:
water-borne preservatives oil-borne preservatives light organic solvent preservatives (LOSPs) In recent years, another fourth category of chemical preservatives for wood, is based upon nanocompounds (i.e. nanometals of boron, copper, silver).
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