Copper (Cu) has been used for centuries to inhibit the reproduction of bacteria and to prevent the growth of many fungi, including Lenzites trabea, Poria monticola and Lentinus lepideus. The role of copper in Permacure CCA is as a primary fungicide and bacteriostatic agent. While it does not directly kill fungicidal or bacterial organisms, it prevents them from using preserved timber as a potential food source, protecting the wood from brown rot (Armillaria), dry rot (Serpula lacrymans) and other wood-destroying bacteria.
Chromium (Cr) acts as a fixation agent within CCA. Due to its presence, the CCA preservative is deeply and permanently bonded to the fundamental chemical components of the wood.
While vacuum-pressure impregnation allows the preservative to penetrate deeply into wood, the chromium ensures that movement of moisture into and out of timber does not remove the preservative.
Arsenic (As) is a naturally abundant metalloid occurring as a common mineral in many important ores and is also present in many types of seafood. It has been known since the 13th century and has since been used as a herbicide, fungicide and insecticide. Arsenic is used in Permacure CCA as both a secondary fungicide, making the wood resistant to even copper-resistant fungi, and also as an insecticide, protecting wood from attack by xylophagous and detrivorous wood borers (Lyctinae); termites (Termopsidae) and other wood-destroying insects.