Editing Lumber (section)

===Preservatives===
{{Main|Wood preservation}}
[[File:Treated timber.jpg|thumb|upright|Special fasteners are used with treated lumber because of the corrosive chemicals used in its preservation process.]]

To avoid decay and termite infestation, untreated wood is separated from the ground and other sources of moisture. These separations are required by many building codes and are considered necessary to maintain wood elements in permanent structures at a safe moisture content for decay protection. When it is not possible to separate wood from the sources of moisture, designers often rely on preservative-treated wood.<ref>{{cite web|url=http://www.woodworks.org/files/PDF/publications/wood-design-durability-service-life-fact-sheet.pdf|title=WoodWorks Durability and Service Life|access-date=2011-06-01|archive-url=https://web.archive.org/web/20120405185524/http://www.woodworks.org/files/PDF/publications/wood-design-durability-service-life-fact-sheet.pdf|archive-date=2012-04-05|url-status=dead}}</ref>

Wood can be treated with a preservative that improves service life under severe conditions without altering its basic characteristics. It can also be pressure-impregnated with fire-retardant chemicals that improve its performance in a fire.<ref>[https://books.google.com/books?id=0SkDAAAAMBAJ&pg=PA59 "Wood That Fights."] ''Popular Sciences'', March 1944, p. 59.</ref> One of the early treatments to "fireproof lumber", which retard fires, was developed in 1936 by the Protexol Corporation, in which lumber is heavily treated with salt.<ref>[https://books.google.com/books?id=lNsDAAAAMBAJ&pg=PA560 "Lumber is Made Fireproof by Salt Treatment" ''Popular Mechanics'', April 1936] bottom-left p. 560</ref> Wood does not deteriorate simply because it gets wet. When wood breaks down, it is because an organism is eating it. Preservatives work by making the food source inedible to these organisms. Properly preservative-treated wood can have 5 to 10 times the service life of untreated wood. Preserved wood is used most often for railroad ties, utility poles, marine piles, decks, fences and other outdoor applications. Various treatment methods and types of chemicals are available, depending on the attributes required in the particular application and the level of protection needed.<ref name="About Treated Wood - CWC">{{cite web|title=About Treated Wood|url=http://cwc.ca/design-with-wood/durability/pressure-treated-wood/about-treated-wood/|archive-url=https://web.archive.org/web/20150203121514/http://cwc.ca/design-with-wood/durability/pressure-treated-wood/about-treated-wood/|url-status=dead|archive-date=3 February 2015|website=CWC|access-date=7 May 2017}}</ref>

There are two basic methods of treating: with and without pressure. Non-pressure methods are the application of preservatives by brushing, spraying, or dipping the piece to be treated. Deeper, more thorough penetration is achieved by driving the preservative into the wood cells with pressure. Various combinations of pressure and vacuum are used to force adequate levels of chemical into the wood. Pressure-treating preservatives consist of chemicals carried in a solvent.
Chromated copper arsenate, once the most commonly used wood preservative in North America began being phased out of most residential applications in 2004. Replacing it are amine copper quat and copper azole.

All wood preservatives used in the United States and Canada are registered and regularly re-examined for safety by the U.S. Environmental Protection Agency and Health Canada's Pest Management and Regulatory Agency, respectively.<ref name="About Treated Wood - CWC"/>