Pressure-treated lumber is wood that has been infused with chemical preservatives to protect it from rot, insects, and weather damage. This process involves placing the wood in a large chamber where air is removed, allowing the preservatives to penetrate deeply into the fibers. As a result, pressure-treated lumber is ideal for outdoor projects like decks, fences, and garden beds. The chemicals used in pressure treatment can vary, but they are designed to extend the lifespan of the wood. While it is durable and resistant to decay, it is important to handle and dispose of pressure-treated lumber properly due to the presence of these chemicals.