Treatment involves chemical preservatives forced deep into the cells in the wood under pressure.
Wood used for decks and other outdoor consumer use is generally treated with an inorganic chemical. In 2004, the EPA outlawed the use of arsenic as a method of treating wood. ACQ and copper azole are the current popular chemicals used.
Treated wood still absorbs water, and the treatment is not considered waterproof, but rather decay-proof.
Wood species typically used include Ponderosa pine, Lodgepole pine, Douglas fir, Hem-fir and Southern yellow pine.
Always wear respiratory protection when cutting treated lumber.