1.1 This guide provides an approach for both the calculation and the substantiation of recycled content of finished packaging paper and paperboard products. A mass balance approach is recommended for use by manufacturers since no physical or chemical test method is currently available to determine absolute recycled content of a finished paper product. 1.2 This guide covers () recycled content of packaging paper and paperboard products that contain any amount or kind of recycled fiber; and () methods to calculate and substantiate the level(s) of recycled fiber content claimed by an agreement between the buyer and the seller. 1.2.1 This guide may be used with or without modification to calculate or substantiate the recycled content of packaging paper and paperboard products when recovered nonfibrous materials (for example, filler) are a part of the recycled fiber furnish. Limited guidance is provided for appropriate modifications to this guide for the determination of amount of recycled nonfibrous materials in paper products. 1.3 This guide does not recommend either an amount or a kind of recycled fiber or material to use since () the amount and kind of recycled content in a packaging paper or paperboard product should be agreed upon between the buyer and the seller, and () the calculation and substantiation procedures recommended may be used for any amount or kind of recycled material agreed upon between the buyer and the seller. 1.4 The mass balance calculation method recommended by this guide may or may not comply with applicable federal, state, or local laws for recycled content statements intended to be received by consumers. Limited guidance on content statements is in Appendix X1. 1.5 The following safety hazards caveat pertains only to the test method portion, Section 10, of this guide: This standard does not purport to address all of the safety concerns, if any,*associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.