This standard specifies the product classification, requirements, test methods, inspection rules and markings, packaging, transportation and storage of co-extrusion rigid polyvinyl chloride (PVC-U) low-foaming sheets. This standard applies to rigid polyvinyl chloride low-foaming sheets (hereinafter referred to as "sheets") made of polyvinyl chloride resin as the main raw material, mixed with various additives, and made by co-extrusion process.