Specified Technology STI SpecSeal® Firestop Pillow

These Pillows Easily Slide In and Out for New or Retrofit Jobs


What's special about this firestop product?

  • Intumescent pillows expand in all directions when activated by extreme heat, for a complete smoke, gas and fire seal.
  • The interior of the pillow is a monolithic encapsulated core, so there is no loose fill to shift and diminish the effectiveness of the protection.
  • You can reuse, remove, and reinstall these in the event you need to change cabling or openings.
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Firestop pillows are perfect for areas that are either medium to large in size, or places where a compressible cushion must be used because of its ability to be easily installed and removed. SpecSeal® Firestop Pillows actually resemble small pillows or bricks, and are highly resilient. Simply install by pressing them into openings and stacking them like bricks.

Part # Dimensions Color Weight Price
STI-SSB14 1"H x 4"W x 9"L (2,5 x 10 x 23 cm) Red 0.18 lb
Manufacturer Direct
STI-SSB24 2"H x 4"W x 9"L (5,0 x 10 x 23 cm) Red 0.27 lb
Manufacturer Direct
STI-SSB26 2"H x 6"W x 9"L (5,0 x 15 x 23 cm) Red 0.35 lb
Manufacturer Direct
STI-SSB36 3"H x 6"W x 9"L (7,5 x 15 x 23 cm) Red 0.48 lb
Manufacturer Direct

Made from a mineral fiber core with a water resistant intumescent membrane, these are great for stopping flames, gases and smoke from entering a space. If you have a difficult one sided area that needs firestopping, this is the ideal product, because it is made for single-sided applications as much as it is for bilateral.

  • Lightweight design makes them easy to work with and install.
  • Made from a heat-treated seamless poly bag that resists tears and remains highly durable during installation.
  • Easy to install because no tools are required

    Ideal for use in:

  • Construction openings that are medium to large in size
  • Around and between cable for power, voice, data and more
  • Around or between cable trays
  • Bus ducts
  • Multiple metallic conduits and tubing
  • Multiple, mixed penetrants of all types
  • STI Firestop Pillow Data Sheet (PDF) PDF

  • Standards:
    Meets ASTM E814 (UL1479) as well as the time-temperature requirements of ASTM E119 (UL 263). This is a three-hour rating for penetrations product which protects through concrete, CMU, or concrete tilt-up walls, as well as concrete or concrete over steel deck floors.

    Air Leakage:
    UL, Underwriters Laboratories, conducted tests for air leakage at ambient and elevated temperatures (400°F (204˚C)) and found that properly installed pillows seal penetrations virtually airtight.


    SSB Series Firestop Pillow
    Color Red
    Standards UL and ULA Listed, FM Approved
    Nom. Density 4 PCF (53 kg/m3)
    Compression** 25% - 33%
    Air Leakage Less than 1 CFM/sq ft
    Rating UL 1479 (Pillows Only)
    VOC Content*** 0.00 lbs/gal (0.0 g/l)
    STC Rating 60
    Shelf Life No Limit
    In Service Temp. <130°F (54°C)
    Flammability* V-0
    * Outer poly bag.
    ** As installed.
    *** ASTM D-3960 and EPA Federal Reference Method 24.


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    How-To Corner




    General: Inspect areas to be protected. Remove any sharp edges or protruding wires or ties that could damage poly bags. Arrange cables (if possible) to present a smooth and even surface. Eliminate large voids by filling with SpecSeal® Firestop Putty at egress from floor or wall surfaces. Calculate pillow requirements in square inches in advance of installation as an indicator of the proper installed volume and compression. See Estimation Table for instructions concerning proper estimation techniques.

    Calculating pillow requirement: Measure the size of the opening to be sealed and calculate the total area of the opening in square inches. Measure and calculate the approximate area occupied by the penetrants. Calculate the net area to be sealed by subtracting the area occupied by the penetrants from the total area of the opening. To allow for the required compression of the pillows, multiply the net area by 1.4. This will provide a compression factor of 29%. In the example shown above, the opening is 12" x 24" with an 18" wide tray. The cable depth in the tray is about 3". The area of the opening is 12 x 24 = 288 sq. in. The approximate area of the cables is 3 x 18 = 54 sq. in. Subtracting the area of the cables from the total area of the opening yields a net area of 234 sq. in. 234 x 1.4 = approx. 328 sq. in. to be filled by pillows. Using the table above to determine the nominal area of the various pillows, we can determine that approximately 28 (328 ÷ 12) SSB26 pillows would be required. The number of pillows required will of course vary by the size of the pillow being utilized. Generally, a small percentage of smaller pillows will be required along with the larger ones. A test opening of this size utilized 24 SSB26 pillows, along with 4 SSB24's and 4 SSB14's.

    NOTE: Removal of cables may require the installation of additional pillows to fill the void created by removing the cables. Inspect pillows for excess compression. Excessive handling or abuse may permanently compress the pillows. If pillows are too thin to apply pressure within the seal when installed, replace thin pillows or add additional new pillows as required.

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