Pressure-treated wood is wood that has been treated with water and preservative chemicals under high pressure to protect it from degradation and decay caused by moisture, threatening organisms such as insects and bacteria, and the elements, therefore extending its lifespan. This type of wood is commonly used for decks and fences and typically arrives damp or wet and may take up to a few weeks to completely dry.
Two common preservative chemicals used in pressure-treated wood include alkaline copper quaternary (ACQ) and copper azole (CA). Care should be taken when handling this type of wood as these chemicals are toxic to both small organisms and humans; this type of wood should only be used in outdoor settings and handled with personal protective equipment.