3M™ Fire Barrier Mortar is a lightweight cementitious firestop with variable mix ratios for use in through penetration applications. It allows up to three hours of fire protection in tested and listed systems.When properly installed, the 3M Fire Barrier Mortar helps prevent the spread of fire, smoke and noxious gases. The mix ratio can be varied from one part water to two parts powder for self-levelling and one part water to three parts powder for trowelable mortar. For vertical surfaces, use three parts mix to one part water.