3M Fire Barrier Moldable Putty Pads MPP+

3M Fire Barrier Moldable Putty Pads MPP+ come in two sizes: 7 x 7 inches and 9.5 x 9.5 inches. The smaller pad covers single-gang metallic or non-metallic boxes; the 9.5 inch pad gives you the extra material for larger or multi-gang boxes. If a box is bigger than one pad, the pads are self-adhering and can be molded together to cover the area, so you are not limited to one pad per opening.

Both. The MPP+ pads are listed for protection of membrane penetrations by listed metallic and non-metallic electrical boxes, so steel and plastic outlet boxes are both covered. The material is non-corrosive to metal, which is why it can sit directly against a steel box without a barrier.

Firestop tested for through penetration and membrane applications up to 4 hours in accordance with ASTM E 814 (UL 1479). For wall opening protection, the pads are tested to ASTM E 119 (UL 263) up to 2 hours when installed per the UL wall-opening protective listing, UL Category CLIV. Those are two different test paths, so match the one your inspector is citing on the drawing.

Yes. MPP+ pads carry an STC rating of 52 when tested on back-to-back electrical boxes, and they also provide a draft and cold smoke seal. That back-to-back condition is the usual sound leak in multi-family demising walls, so pads on both boxes address the fire rating and the noise path at the same time.

No tools and no mixing. The pads are a one-part intumescent material supplied ready to use at 1/10 inch (2.54 mm) thick, and technicians mold them by hand directly onto the substrate. They adhere to a wide range of construction materials, and multiple pads press together for bigger areas. Nothing else is required to complete the application.

Putty pads are the right call when the geometry is irregular: gaps between cables in multiple penetrations including fiber optic inner duct, insulated pipe, electrical conduit and metal pipe. The material conforms by hand to coverage that strips, wraps or rolls cannot practically follow. It is also compatible with synthetic cable jackets, so it can go straight against the cable. For a plastic pipe that needs to collapse the bore as it melts, a dedicated wrap strip or collar is the product type to look at instead.

Yes, MPP+ is re-enterable after installation, so you can open the penetration to add or replace cable and re-mold the material back over it. It also will not crumble or dry out and has aging properties suited to long-term installed service, so an older pad is generally still workable.

No. The MPP+ putty pads are not watertight. They provide a fire, draft and cold smoke seal, not a water seal, so do not specify them where the penetration also has to hold back water.

Red. The red color is how inspectors spot firestop material on a membrane penetration at a glance, which is useful when a whole floor of boxes has to be verified before drywall closes in.