3M fire barrier composite sheet is a thin one-part composite system designed to fire stop blank openings and larger penetrations such as cable trays, conduits and HVAC ductwork through rated construction. It expands with heat to form a hard char that tightly seals penetrations against flame spread, smoke and toxic gases. It measures of 52 in. x 28 in. x 0.30 in. It is non-flame supporting and thermally conductive, allows unwanted heat build-up to escape. It is easy to install using common trade tools and is re-enterable for new or retrofit installations.