Wood preservation is the pressure or thermal impregnation of chemicals into wood to a depth that will provide effective long-term resistance attack by fungi, insects, and marine borers. The chemical predominantly used in Canada for wood preservation are pentachlorophenol, creosote, and aqueous formulations of arsenic, copper, chromium or ammonia. The wood preservation process deposits or fixes these chemicals in the wood, and the toxic nature of the chemicals effectively prevents the attack of living organisms on the wood. Because the chemicals are also toxic in varying degrees to humans and aquatic organisms, their use in industry must be carefully controlled. This document is intended to provide consistent guidelines for the design and operation of wood preservation facilities in a manner that will protect workers and the environment from harmful exposure to wood preservation chemicals.