Wood is an environmentally sound, economical building material that can be used either indoors or outdoors for a wide variety of structural and decorative applications. Unfortunately, untreated lumber cut from most commercially harvested tree species is subject to attack by insects or to decay caused by fungi and bacteria. The decay or insect hazard is greatest in exposures where the wood is subjected to moisture. Wood in outdoor exposures, either in ground-contact or in above-ground applications, is susceptible to attack. The potential for wood deterioration is greatest in hot and humid climates, which allow insects, fungi and bacteria to thrive. Destruction of untreated wood in aquatic environments can be caused by a variety of marine organisms. Wood should be treated with a preservative system to control the destructive activities of these organisms and ensure long-term structural soundness and serviceability.