Ammoniacal copper quaternary （ACQ） is a wood preservative being used as a （replacement） for the preservative chromated copper arsenate （CCA） that is being phased out. This article presents the basic physical and chemical properties, performance statistics, safety to （humans,） animals and the environment from ACQ. It also covers treating methods, handling （procedures）, the effect ACQ has on wood properties, and recommendations on how and where it should be used. The purpose of this article is to present information showing that ACQ is a very good preservative for treated wood products and works very well when used in them.