3M Fire Block Sealant FB 136 is a one component, non-combustible draft, smoke and fire blocking sealant, designed to resist high temperatures and smoke passage in nonrated construction. Use 3M Fire Block Sealant FB 136 to seal interior construction voids around wires, pipes, HVAC ducts and vents, in wood or steel framed non-rated construction. This fire block is tack-free in approximately 15 minutes and features minimal shrinkage and sag-resistant formulation to help ensure longevity, plus a halogen-free formula. This fire block also provides excellent adhesion that bonds to concrete, brick, metals, wood, plastic and cable jacketing.
Tested as a type V residential Fireblock to ASTM E 84 (modified)
Durable caulk is heat-resistant (up to 240°F/115°C)
Tack-free in approximately 15 minutes
Meets International Building Code (IBC) and International Residential Code (IRC) fire blocking requirements

Intumescent = sealant swells up when heated, thus selaing the gap in the event of fire.