F Rating 1 : A rating usually expressed in hours indicating a specific length of time that a fire-resistive barrier can withstand fire before being consumed or before permitting the passage of flame through an opening in the assembly
William J. McHugh, Jr., Glossary of Firestop Terms (Article, Life Safety Digest magazine), Firestop Contractors International Association FCIA, Hillside, IL, USA 2010. http://www.fcia.org/articles/glossary.htm , (Firestop - Amer) {511}