Look for a lumber end tag. Each piece of ProWood lumber has a tag containing information regarding the preservative used, the appropriate end use (i.e. above-ground or ground contact), the quality standard and safe handling instructions.
In some cases, building code regulations mandate the use of treated wood that meets certain standards. The International Code Council (ICC) develops model building codes for use nationwide. ProWood has been determined by the ICC-ES to be code compliant with the details listed under the ESR-1980 Report (pdf – 257 KB), ESR-2240 Report (pdf – 309 KB) and the ESR-1721 Report (pdf – 107 KB). In the case of treated wood, the ICC relies primarily on the American Wood Protection Association (AWPA) to determine appropriate standards of treatment for specific preservatives in specific end uses. They also offer their own ICC Evaluation Service as a way to determine if a product is suitable. Quality control measures are designed to ensure the treated wood produced meets the quality standards. In addition to in-house quality checking, manufacturers are also required to subscribe to an independent inspection agency, which verifies the wood was treated in accordance with the applicable standards. Manufacturers who are in good standing with the third party inspection agency will carry that agency's quality mark on the lumber end tag.
For an independent viewpoint on how to tell if your wood is properly treated, view the USDA's Forest Products Laboratory TechLine on new wood treatments.